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Tópico: Physical Geography

  1. #1
    Gforum Veterano
    Data de Ingresso
    Apr 2007

    Padrão Physical Geography

    Physical geography (also known as geosystems or physiography) is one of the two major subfields of geography. Physical geography focuses on understanding the processes and patterns in the natural environment, as opposed to the built environment which is the domain of Human geography. Within the body of physical geography the Earth is often split either into several spheres or into different environments, with the main spheres being the; Atmosphere, Biosphere, Cryosphere, Geosphere, Hydrosphere, Lithosphere and Pedosphere. Within physical geography there are various fields of study, mainly but not exclusively focusing on the spheres of the earth. Research in physical geography is often interdisciplinary and uses the systems approach.

    Earth Map

    Fields of physical geography

    * Geomorphology is the science concerned with understanding the surface of the Earth and the processes by which it is shaped, both at the present as well as in the past. Geomorphology as a field has several sub-fields that deal with the specific landforms of various environments e.g. desert geomorphology and fluvial geomorphology, however, these sub-fields are united by the core processes which cause them; mainly tectonic or climatic processes. Geomorphology seeks to understand landform history and dynamics, and predict future changes through a combination of field observation, physical experiment, and numerical modeling (Geomorphometry). Early studies in geomorphology are the foundation for pedology, one of two main branches of soil science.

    Natural Arch

    * Hydrology is predominantly concerned with the amounts and quality of water moving and accumulating on the land surface and in the soils and rocks near the surface and is typified by the hydrological cycle. Thus the field encompasses water in rivers, lakes, aquifers and to an extent glaciers, in which the field examines the process and dynamics involved in these bodies of water. Hydrology originated from engineering and has thus developed a largely quantitative method in its research, however, it does have an earth science side that embraces the systems approach. Similar to most fields of physical geography it has sub-fields that examine the specific bodies of water or their interaction with other spheres e.g. limnology and ecohydrology.

    Meander Formation

    * Glaciology is the study of glaciers and ice sheets, or more commonly the cryosphere or ice and phenomena that involve ice. Glaciology groups the latter (ice sheets) as continental glaciers and the former (glaciers) as alpine glaciers. Although, research in the areas are similar with research undertaken into both the dynamics of ice sheets and glaciers the latter tends to be concerned with the interaction of ice sheets with the present climate and the latter with the impact of glaciers on the landscape. Glaciology also has a vast array of sub-fields examining the factors and processes involved in ice sheets and glaciers e.g. snow hydrology and glacial geology.

    Alpine Glaciar

    * Biogeography is the science which deals with geographic patterns of species distribution and the processes that result in these patterns. Biogeography emerged as a field of study as a result of the work of Alfred Russel Wallace, although the field prior to the late twentieth century had largely been viewed as historic in its outlook and descriptive in its approach. The main stimulus for the field since its founding has been that of evolution, plate tectonics and the theory of island biogeography. The field can largely be divided into five sub-fields: island biogeography, paleobiogeography, phylogeography, zoogeography and phytogeography

    Wallace Line

    * Climatology is the study of the climate, scientifically defined as weather conditions averaged over a long period of time. As opposed to meteorology which studies atmospheric processes over a shorter duration, which are then examined by climatologist to find trends and frequencies in weather patterns/ phenomena. Climatology, examines both the nature of micro (local) and macro (global) climates and the natural and anthropogenic influences on them. The field is also sub-divided largely into the climates of various regions and the study of specific phenomena or time periods e.g. tropical cyclone rainfall climatology and paleoclimatology.

    Climate Trends

    * Pedology is the study of soils in its natural environment. It is one of two main branches of soil science, the other being edaphology. Pedology mainly deals with pedogenesis, soil morphology, soil classification. In physical geography pedology is largely studied due to the numerous interactions between climate (water, air, temperature), soil life (micro-organisms, plants, animals), the mineral materials within soils (biogeochemical cycles) and its position and effects on the landscape such as laterization.

    Nitrogen Cycle

    * Palaeogeography is the study of the distribution of the continents through geologic time through examining the preserved material in the stratigraphic record. Palaeogeography is a cross-discipline, almost all the evidence for the positions of the continents comes from geology in the form of fossils or geophysics the use of this data has resulted in evidence for continental drift, plate tectonics and supercontinents this in turn has supported palaeogeographic theories such as the Wilson cycle.

    * Coastal geography is the study of the dynamic interface between the ocean and the land, incorporating both the physical geography (i.e coastal geomorphology, geology and oceanography) and the human geography of the coast. It involves an understanding of coastal weathering processes, particularly wave action, sediment movement and weathering, and also the ways in which humans interact with the coast. Coastal geography although predominantly geomorphological in its research is not just concerned with coastal landforms, but also the causes and influences of sea level change.

    High Energy coastline

    * Oceanography is the branch of physical geography that studies the Earth's oceans and seas. It covers a wide range of topics, including marine organisms and ecosystem dynamics (biological oceanography); ocean currents, waves, and geophysical fluid dynamics (physical oceanography); plate tectonics and the geology of the sea floor (geological oceanography); and fluxes of various chemical substances and physical properties within the ocean and across its boundaries (chemical oceanography). These diverse topics reflect multiple disciplines that oceanographers blend to further knowledge of the world ocean and understanding of processes within it.

    Thermohaline circulation

    * Quaternary science is an inter-disciplinary field of study focusing on the Quaternary period, which encompasses the last 2.6 million years. The field studies the last ice age and the recent interstadial the Holocene and uses proxy evidence to reconstruct the past environments during this period to infer the climatic and environmental changes that have occurred.

    * Landscape ecology is a sub-discipline of ecology and geography that address how spatial variation in the landscape affects ecological processes such as the distribution and flow of energy, materials and individuals in the environment (which, in turn, may influence the distribution of landscape "elements" themselves such as hedgerows). The field was largely founded by the German geographer Carl Troll Landscape ecology typically deals with problems in an applied and holistic context. The main difference between biogeography and landscape ecology is that the latter is concerned with how flows or energy and material are changed and their impacts on the landscape whereas the former is concerned with the spatial patterns of species and chemical cycles.

    Habitat Fragmentation

    * Geomatics is the filed of gathering, storing, processing, and delivering of geographic information, or spatially referenced information. Geomatrics includes geodesy (scientific discipline that deals with the measurement and representation of the earth, its gravitational field, and other geodynamic phenomena, such as crustal motion, oceanic tides, and polar motion) and G.I.S. (a system for capturing, storing, analyzing and managing data and associated attributes which are spatially referenced to the earth) and remote sensing (the short or large-scale acquisition of information of an object or phenomenon, by the use of either recording or real-time sensing device(s) that is not in physical or intimate contact with the object).

    Digital Elevation Model

    * Environmental geography is a branch of geography that describes the spatial aspects of interactions between humans and the natural world. The branch bridges the divide between human and physical geography and thus requires an understanding of the dynamics of geology, meteorology, hydrology, biogeography, and geomorphology, as well as the ways in which human societies conceptualize the environment. Although the branch was previously more visible in research than at present with theories such as environmental determinism linking society with the environment. It has largely become the domain of the study of environmental management or anthropogenic influences on the environment and vice a versa.


    Physical geography literature

    Physical geography and Earth Science journals communicate and document the results of research carried out in universities and various other research institutions. Most journals cover a specific field and publish the research within that field, however unlike human geographers, physical geographers tend to publish in inter-disciplinary journals rather than predominantly geography journal; the research is normally expressed in the form of a scientific paper. Additionally, textbooks books and magazines on geography communicate research to laypeople, although these tend to focus on environmental issues or cultural dilemmas. Examples of journals that publish articles from physical geographers are:

    * Earth Surface Processes and Landforms
    * Journal of Biogeography
    * Journal of Quaternary Science
    * Geomorphology

    * Polar Research
    * The Professional Geographer
    * Transactions of the Institute of British Geographers

    * Bulletin of the American Meteorological Society
    * Climatic Change
    * Earth Interactions

    * Journal of Climate
    * Geophysical Research Letters
    * Journal of Hydrometeorology
    * GeoJournal

    Última edição por Freundlich; 11-05-2008 às 08:48.

  2. #2
    Gforum Veterano
    Data de Ingresso
    Apr 2007

    Padrão Continents

    A continent is one of several large landmasses on Earth. They are generally identified by convention rather than any strict criteria, but seven areas are commonly regarded as continents – they are (from largest in size to smallest): Asia, Africa, North America, South America, Antarctica, Europe, and Australia.


    Dymaxion Map

    "Continents are understood to be large, continuous, discrete masses of land, ideally separated by expanses of water." However, many of the seven most commonly recognized continents are identified by convention rather than adherence to the ideal criterion that each be a discrete landmass, separated by water from others. Likewise, the criterion that each be a continuous landmass is often disregarded by the inclusion of the continental shelf and oceanic islands. The Earth's major landmasses are washed upon by a single, continuous World Ocean, which is divided into a number of principal oceanic components by the continents and various geographic criteria.

    Plate tectonics is the geological process and study of the movement, collision and division of continents, earlier known as continental drift.

    The term "the Continent" (capitalized), used predominantly in the European isles and peninsulas, such as the British Isles, Sardinia, Sicily and the Scandinavian Peninsula, means mainland Europe, although it can also mean Asia when said in Japan.

    he narrowest meaning of continent is that of a continuous area of land or mainland, with the coastline and any land boundaries forming the edge of the continent. In this sense the term continental Europe is used to refer to mainland Europe, excluding islands such as Great Britain, Ireland, and Iceland, and the term continent of Australia may refer to the mainland of Australia, excluding Tasmania. Similarly, the continental United States refers to the 48 contiguous United States in central North America and may include Alaska in the northwest of the continent (both separated by Canada), while excluding Hawaii in the middle of the Pacific Ocean.

    From the perspective of geology or physical geography, continent may be extended beyond the confines of continuous dry land to include the shallow, submerged adjacent area (the continental shelf) and the islands on the shelf (continental islands), as they are structurally part of the continent. From this perspective the edge of the continental shelf is the true edge of the continent, as shorelines vary with changes in sea level. In this sense the islands of Great Britain and Ireland are part of Europe, and Australia and the island of New Guinea together form a continent (Australia-New Guinea).

    As a cultural construct, the concept of a continent may go beyond the continental shelf to include oceanic islands and continental fragments. In this way, Iceland is considered part of Europe and Madagascar part of Africa. Extrapolating the concept to its extreme, some geographers take Australia, New Zealand and all the islands of Oceania (or sometimes Australasia) to be equivalent to a continent, allowing the entire land surface of the Earth to be divided into continents or quasi-continents.

    The ideal criterion that each continent be a discrete landmass is commonly disregarded in favor of more arbitrary, historical conventions. Of the seven most commonly recognized continents, only Antarctica and Australia are separated from other continents.

    Several continents are defined not as absolutely distinct bodies but as "more or less discrete masses of land". Asia and Africa are joined by the Isthmus of Suez, and North and South America by the Isthmus of Panama. Both these isthmuses are very narrow in comparison with the bulk of the landmasses they join, and both are transected by artificial canals (the Suez Canal and Panama Canal, respectively) which effectively separate these landmasses.

    The division of the landmass of Eurasia into the continents of Asia and Europe is an anomaly, as no sea separates them. The distinction is maintained for historical and cultural reasons. An alternative view is that Eurasia is a single continent, one of six continents in total. This view is held by some geographers and is preferred in Russia (which spans Asia and Europe).

    North America and South America are now treated as separate continents in much of Western Europe, India, China, and most native English-speaking countries, such as the United States, Canada, Australia, and New Zealand[citation needed]. Furthermore, the concept of two American continents is prevalent in much of Asia. However, in earlier times they were viewed as a single continent known as America or, to avoid ambiguity with the United States of America, as the Americas. However, the plurality of this last term suggests that even in these "earlier times" some considered the New World (the Americas) as two separate continents. North and South America are viewed as a single continent, one of six in total, in some parts of Europe, and much of Latin America.

    When continents are defined as discrete landmasses, embracing all the contiguous land of a body, then Asia, Europe and Africa form a single continent known by various names such as Afro-Eurasia. This produces a four-continent model consisting of Afro-Eurasia, the Americas, Antarctica and Australia.

    When sea levels were lower during the Pleistocene ice age, greater areas of continental shelf were exposed as dry land, forming land bridges. At this time Australia-New Guinea was a single, continuous continent. Likewise North America and Asia were joined by the Bering land bridge. Other islands such as Great Britain were joined to the mainlands of their continents. At that time there were just three discrete continents: Afro-Eurasia-America, Antarctica and Australia-New Guinea.

    The seven-continent model is usually taught in Western Europe, Northern Europe, Central Europe, Southeastern Europe, China and most English-speaking countries. The six-continent combined-Eurasia model is preferred by the geographic community, Russia, Eastern Europe, and Japan. The six-continent combined-America model is taught in Latin America, the Iberian Peninsula, Italy, Iran, Greece and some other parts of Europe. This model may be taught to include only the five inhabited continents (excluding Antarctica) — as depicted in the Olympic logo.

    The names Oceania or Australasia are sometimes used in place of Australia. For example, the Atlas of Canada names Oceania, as does the model taught in Latin America and Iberia.

    Última edição por Freundlich; 11-05-2008 às 09:08.

  3. #3
    Gforum Veterano
    Data de Ingresso
    Apr 2007

    Padrão Asia

    Asia is the world's largest and most populous continent. It covers 8.6% of the Earth's total surface area (or 29.4% of its land area) and, with over 4 billion people, it contains more than 60% of the world's current human population. Chiefly in the eastern and northern hemispheres, Asia is traditionally defined as part of the landmass of Eurasia—with the western portion of the latter occupied by Europe—lying east of the Suez Canal, east of the Ural Mountains, and south of the Caucasus Mountains and the Caspian and Black Seas. It is bounded on the east by the Pacific Ocean, on the south by the Indian Ocean, and on the north by the Arctic Ocean. Given its size and diversity, Asia—a toponym dating back to classical antiquity—is more a cultural concept incorporating a number of regions and peoples than a homogeneous physical entity (see Subregions of Asia, Asian people).

    Location Asia

    The word Asia originated from the Ancient Greek word "Ασία", first attributed to Herodotus (about 440 BC) in reference to Anatolia or, for the purposes of describing the Persian Wars, to the Persian Empire, in contrast to Greece and Egypt. Herodotus comments that he is puzzled as to why three women's names are used to describe one enormous and substantial land mass (Europa, Asia, and Libya, referring to Africa), stating that most Greeks assumed that Asia was named after the wife of Prometheus but that the Lydians say it was named after Asias, son of Cotys who passed the name on to a tribe in Sardis.

    Even before Herodotus, Homer knew of a Trojan ally named Asios and elsewhere he describes a marsh as ασιος (Iliad 2, 461). The Greek term may be derived from Assuwa, a 14th century BC confederation of states in Western Anatolia. Hittite assu-—"good" is probably an element in that name.

    Alternatively, the etymology of the term may be from the Akkadian word (w)aṣû(m), which means "to go outside" or "to ascend", referring to the direction of the sun at sunrise in the Middle East, and also likely connected with the Phoenician word asa meaning east. This may be contrasted to a similar etymology proposed for Europe, as being from Akkadian erēbu(m) "to enter" or "set" (of the sun). However, this etymology is considered doubtful, because it does not explain how the term "Asia" first came to be associated with Anatolia, which is west of the Semitic-speaking areas, unless they refer to the viewpoint of a Phoenician sailor sailing through the straits between the Mediterranean Sea and the Black Sea.

    It is interesting to note, in Icelandic Saga, ancient Teutons separated Asia from Europe by the river Tanakvisl (or Vanakvisl), which flows into the Black Sea. Eastward across the River (in Asia), so legend tells, was a land known as Asaheim or Asaland, where dwelt Odin, chief god, in his citadel named Asgard. However, Aesir and all its forms are related to Sanskrit asura and Avestan ahura, the local reflexes of the name of a class of divine beings.

    Definition and boundaries

    Medieval Europeans considered Asia as a continent – a distinct landmass. The European concept of the three continents in the Old World goes back to Classical Antiquity, but during the Middle Ages was notably due to Isidore of Sevilla (see T and O map). The demarcation between Asia and Africa (to the southwest) is the Isthmus of Suez and the Red Sea. The boundary between Asia and Europe is conventionally considered to run through the Dardanelles, the Sea of Marmara, the Bosporus, the Black Sea, the Caucasus Mountains, the Caspian Sea, the Ural River to its source, and the Ural Mountains to the Kara Sea near Kara, Russia. While this interpretation of tripartite continents (i.e., of Asia, Europe, and Africa) remains common in modernity, discovery of the extent of Africa and Asia have made this definition somewhat anachronistic. This is especially true in the case of Asia, which would have several regions that would be considered distinct landmasses if these criteria were used (for example, Southern Asia and Eastern Asia).

    In the far northeast of Asia, Siberia is separated from North America by the Bering Strait. Asia is bounded on the south by the Indian Ocean (specifically, from west to east, the Gulf of Aden, Arabian Sea, and Bay of Bengal); on the east by the waters of the Pacific Ocean (including, counterclockwise, the South China Sea, East China Sea, Yellow Sea, Sea of Japan, Sea of Okhotsk, and Bering Sea); and on the north by the Arctic Ocean. Australia (or Oceania) is to the southeast.

    Asia Map excluding Southwest Asia

    Some geographers do not consider Asia and Europe to be separate continents, as there is no logical physical separation between them. Geographically, Asia is the major eastern constituent of the continent of Eurasia – with Europe being a northwestern peninsula of the landmass – or of Afro-Eurasia: geologically, Asia, Europe, and Africa comprise a single continuous landmass (save the Suez Canal) and share a common continental shelf. Almost all of Europe and most of Asia sit atop the Eurasian Plate, adjoined on the south by the Arabian and Indian Plates, and with the easternmost part of Siberia (east of the Cherskiy Range) on the North American Plate.

    In geography, there are two schools of thought. One school follows historical convention and treats Europe and Asia as different continents, categorizing subregions within them for more detailed analysis. The other school equates the word "continent" with a geographical region when referring to Europe, and use the term "region" to describe Asia in terms of physiography. Since, in linguistic terms, "continent" implies a distinct landmass, it is becoming increasingly common to substitute the term "region" for "continent" to avoid the problem of disambiguation altogether.

    Given the scope and diversity of the landmass, it is sometimes not even clear exactly what "Asia" consists of. Some definitions exclude Turkey, the Middle East, Central Asia, and Russia while only considering the Far East, Southeast Asia and the Indian subcontinent to compose Asia, especially in the United States after World War II. The term is sometimes used more strictly in reference to the Asia-Pacific region, which does not include the Middle East or Russia, but does include islands in the Pacific Ocean—a number of which may also be considered part of Australasia or Oceania, although Pacific Islanders are commonly not considered Asian.

    "Asian" as a demonym

    See also: Geography of Asia, countries in both Asia and Europe, geographic criteria for the definition of Europe, orientalism.

    The demonym "Asian" is often used colloquially to refer to people from a subregion of Asia instead of for anyone from Asia. Thus, in British English, "Asian" can mean South Asian, but may also refer to other Asian groups. In the United States, "Asian American" can mean East Asian Americans, due to the historical and cultural influences of China and Japan on the U.S. up to the 1960s and in preference to the terms "Oriental" and "Asiatic". However, the term is increasingly taken to include Southeast Asian Americans and South Asian Americans, due to the increasing numbers of them.

    Territories and regions


  4. #4
    Gforum Veterano
    Data de Ingresso
    Apr 2007

    Padrão Africa

    Africa is the world's second-largest and second most-populous continent, after Asia. At about 30.2 million km² (11.7 million sq mi) including adjacent islands, it covers 6 percent of the Earth's total surface area and 20.4 percent of the total land area. With about 922 million people (as of 2005) in 61 territories, it accounts for about 14.2 percent of the world's human population. The continent is surrounded by the Mediterranean Sea to the north, the Suez Canal and the Red Sea to the northeast, the Indian Ocean to the southeast, and the Atlantic Ocean to the west. There are 46 countries including Madagascar, and 53 including all the island groups.

    Africa location
    Africa, particularly central eastern Africa, is widely regarded within the scientific community to be the origin of humans and the Hominidae tree (great apes), as evidenced by the discovery of the earliest hominids and their possible ancestors, as well as later ones that have been dated to around seven million years ago – including Sahelanthropus tchadensis, Australopithecus africanus, A. afarensis, Homo erectus, H. habilis and H. ergaster – with the earliest Homo sapiens (human) found in Ethiopia being dated to ca. 200,000 years ago.

    Africa straddles the equator and encompasses numerous climate areas; it is the only continent to stretch from the northern temperate to southern temperate zones. Because of the lack of natural regular precipitation and irrigation as well as glaciers or mountain aquifer systems, there is no natural moderating effect on the climate except near the coasts.


    Afri was the name of several peoples who dwelt in North Africa near Carthage. Their name is usually connected with Phoenician afar, "dust", but a 1981 theory has asserted that it stems from a Berber word ifri meaning "cave", in reference to cave dwellers.

    In Roman times, Carthage became the capital of Africa Province, which also included the coastal part of modern Libya. The Roman suffix "-ca" denotes "country or land". The later Muslim kingdom of Ifriqiya, modern-day Tunisia, also preserved a form of the name.

    Other etymologies that have been postulated for the ancient name "Africa":

    * the 1st-century Jewish historian Flavius Josephus (Ant. 1.15) asserted that it was named for Epher, grandson of Abraham according to Gen. 25:4, whose descendants, he claimed, had invaded Libya.
    * the Latin word aprica, meaning "sunny", mentioned by Isidore of Seville (sixth century) in Etymologiae XIV.5.2
    * the Greek word aphrike, meaning "without cold." This was proposed by historian Leo Africanus (1488–1554), who suggested the Greek word phrike (φρίκη, meaning "cold and horror"), combined with the privative prefix "a-", thus indicating a land free of cold and horror.

    The Irish female name Aifric is sometimes Anglicised as Africa, but the personal name is unrelated to the geonym: Latin references to a place called Africa predate the Romans' first encounters with Celtic tribes and their languages by many years.

    Africa is the largest of the three great southward projections from the main mass of the Earth's exposed surface. Separated from Europe by the Mediterranean Sea, it is joined to Asia at its northeast extremity by the Isthmus of Suez (transected by the Suez Canal), 163 km (101 miles) wide. (Geopolitically, Egypt's Sinai Peninsula east of the Suez Canal is often considered part of Africa, as well. ) From the most northerly point, Ras ben Sakka in Tunisia (37°21' N), to the most southerly point, Cape Agulhas in South Africa (34°51'15" S), is a distance of approximately 8,000 km (5,000 miles);[9] from Cape Verde, 17°33'22" W, the westernmost point, to Ras Hafun in Somalia, 51°27'52" E, the most easterly projection, is a distance of approximately 7,400 km (4,600 miles).[10] The coastline is 26,000 km (16,100 miles) long, and the absence of deep indentations of the shore is illustrated by the fact that Europe, which covers only 10,400,000 km² (4,010,000 square miles) – about a third of the surface of Africa – has a coastline of 32,000 km (19,800 miles).

    Africa's largest country is Sudan, and its smallest country is the Seychelles, an archipelago off the east coast. The smallest nation on the continental mainland is The Gambia.

    In the late nineteenth century, the European imperial powers engaged in a major territorial scramble and occupied most of the continent, creating many colonial nation states, and leaving only two independent nations: Liberia, an independent state partly settled by African Americans; and Orthodox Christian Ethiopia (known to Europeans as "Abyssinia"). Colonial rule by Europeans would continue until after the conclusion of World War II, when all colonial states gradually obtained formal independence.

    Colonialism had a destabilising effect on a number of ethnic groups that is still being felt in African politics. Before European influence, national borders were not much of a concern, with Africans generally following the practice of other areas of the world, such as the Arabian Peninsula, where a group's territory was congruent with its military or trade influence. The European insistence of drawing borders around territories to isolate them from those of other colonial powers often had the effect of separating otherwise contiguous political groups, or forcing traditional enemies to live side by side with no buffer between them. For example, although the Congo River appears to be a natural geographic boundary, there were groups that otherwise shared a language, culture or other similarity living on both sides. The division of the land between Belgium and France along the river isolated these groups from each other. Those who lived in Saharan or Sub-Saharan Africa and traded across the continent for centuries often found themselves crossing borders that existed only on European maps.

    In nations that had substantial European populations, for example Rhodesia (now Zimbabwe) and South Africa, systems of second-class citizenship were often set up in order to give Europeans political power far in excess of their numbers. In the Congo Free State, personal property of King Leopold II of Belgium, the native population was submitted to inhumane treatment, and a near slavery status assorted with forced labor. However, the lines were not always drawn strictly across racial lines. In Liberia, citizens who were descendants of American slaves had a political system for over 100 years that gave ex-slaves and natives to the area roughly equal legislative power despite the fact the ex-slaves were outnumbered ten to one in the general population.

    Europeans often altered the local balance of power, created ethnic divides where they did not previously exist, and introduced a cultural dichotomy detrimental to the native inhabitants in the areas they controlled. For example, in what are now Rwanda and Burundi, two ethnic groups Hutus and Tutsis had merged into one culture by the time German colonists had taken control of the region in the nineteenth century. No longer divided by ethnicity as intermingling, intermarriage, and merging of cultural practices over the centuries had long since erased visible signs of a culture divide, Belgium instituted a policy of racial categorization upon taking control of the region, as racially based categorization and philosophies were a fixture of the European culture of that time. The term Hutu originally referred to the agricultural-based Bantu-speaking peoples that moved into present day Rwanda and Burundi from the West, and the term Tutsi referred to Northeastern cattle-based peoples that migrated into the region later. The terms described a person's economic class; individuals who owned roughly 10 or more cattle were considered Tutsi, and those with fewer were considered Hutu, regardless of ancestral history. This was not a strict line but a general rule of thumb, and one could move from Hutu to Tutsi and vice versa.

    The Belgians introduced a racialized system; European-like features such as fairer skin, ample height, narrow noses were seen as more ideally Hamitic, and belonged to those people closest to Tutsi in ancestry, who were thus given power amongst the colonised peoples. Identity cards were issued based on this philosophy.

    Tunisia was the first country in Africa to gain Independence, doing so in 1956. The decades-long struggle for independence from France was led by Habib Bourguiba, founder of the Republic of Tunisia.

    Map showing European territorial claims on the African continent in 1914

    The African Union (AU) is a federation consisting of all of Africa's states except Morocco. The union was formed, with Addis Ababa as its headquarters, on June 26, 2001. In July 2004, the African Union's Pan-African Parliament (PAP) was relocated to Midrand, in South Africa, but the African Commission on Human and Peoples' Rights remained in Addis Ababa. There is a policy in effect to decentralise the African Federation's institutions so that they are shared by all the states.

    The African Union, not to be confused with the AU Commission, is formed by an Act of Union which aims to transform the African Economic Community, a federated commonwealth, into a state, under established international conventions. The African Union has a parliamentary government, known as the African Union Government, consisting of legislative, judicial and executive organs, and led by the African Union President and Head of State, who is also the President of the Pan African Parliament. A person becomes AU President by being elected to the PAP, and subsequently gaining majority support in the PAP.

    President Gertrude Ibengwe Mongella is the Head of State and Chief of Government of the African Union, by virtue of the fact that she is the President of the Pan African Parliament. She was elected by Parliament in its inaugural session in March 2004, for a term of five years. The PAP consists of 265 legislators, five from each constituent state of the African Union. Over 21% of the members are female.[citation needed]

    The powers and authority of the President of the African Parliament derive from the Union Act, and the Protocol of the Pan African Parliament, as well as the inheritance of presidential authority stipulated by African treaties and by international treaties, including those subordinating the Secretary General of the OAU Secretariat (AU Commission) to the PAP. The government of the AU consists of all-union (federal), regional, state, and municipal authorities, as well as hundreds of institutions, that together manage the day-to-day affairs of the institution.

    Failed state policies, inequitable global trade practices, and climatic conditions (especially drought) have resulted in many widespread famines, and significant portions of Africa remain with distribution systems unable to disseminate enough food or water for the population to survive. What had before colonialism been the source for 90% of the world's gold has become the poorest continent on earth, its former riches enjoyed by those on other continents. The spread of disease is also rampant, especially the spread of the HIV and the associated AIDS, which has become a deadly pandemic on the continent.

    There are clear signs of increased networking among African organisations and states. In the civil war in the Democratic Republic of the Congo (former Zaire), rather than rich, non-African countries intervening, neighbouring African countries became involved (see also Second Congo War). Since the conflict began in 1998, the estimated death toll has reached 4 million. Political associations such as the African Union offer hope for greater co-operation and peace between the continent's many countries. Extensive human rights abuses still occur in several parts of Africa, often under the oversight of the state. Most of such violations occur for political reasons, often as a side effect of civil war. Countries where major human rights violations have been reported in recent times include the Democratic Republic of the Congo, Sierra Leone, Liberia, Sudan, Zimbabwe, and Côte d'Ivoire.

    The last 40 years have seen a rapid increase in population; hence, this population is relatively young. In some African states half or more of the population is under 25 years old.[45]

    Speakers of Bantu languages (part of the Niger-Congo family) are the majority in southern, central and East Africa proper. But there are also several Nilotic groups in East Africa, and a few remaining indigenous Khoisan ('San' or 'Bushmen') and Pygmy peoples in southern and central Africa, respectively. Bantu-speaking Africans also predominate in Gabon and Equatorial Guinea, and are found in parts of southern Cameroon and southern Somalia. In the Kalahari Desert of Southern Africa, the distinct people known as the Bushmen (also "San", closely related to, but distinct from "Hottentots") have long been present. The San are physically distinct from other Africans and are the indigenous people of southern Africa. Pygmies are the pre-Bantu indigenous peoples of central Africa.

    The peoples of North Africa comprise two main groups; Berber and Arabic-speaking peoples in the west, and Egyptians in the east. The Arabs who arrived in the seventh century introduced the Arabic language and Islam to North Africa. The Semitic Phoenicians, the European Greeks, Romans and Vandals settled in North Africa as well. Berbers still make up the majority in Morocco, while they are a significant minority within Algeria. They are also present in Tunisia and Libya. The Tuareg and other often-nomadic peoples are the principal inhabitants of the Saharan interior of North Africa. Nubians are a Nilo-Saharan-speaking group (though many also speak Arabic), who developed an ancient civilisation in northeast Africa.

    During the past century or so, small but economically important colonies of Lebanese and Chinese have also developed in the larger coastal cities of West and East Africa, respectively.

    Some Ethiopian and Eritrean groups (like the Amhara and Tigrayans, collectively known as "Habesha") speak Semitic languages. The Oromo and Somali peoples speak Cushitic languages, but some Somali clans trace their founding to legendary Arab founders. Sudan and Mauritania are divided between a mostly Arabized north and a native African south (although the "Arabs" of Sudan clearly have a predominantly native African ancestry themselves). Some areas of East Africa, particularly the island of Zanzibar and the Kenyan island of Lamu, received Arab Muslim and Southwest Asian settlers and merchants throughout the Middle Ages and in antiquity.

    Beginning in the sixteenth century, Europeans such as the Portuguese and Dutch began to establish trading posts and forts along the coasts of western and southern Africa. Eventually, a large number of Dutch augmented by French Huguenots and Germans settled in what is today South Africa. Their descendants, the Afrikaners and the Coloureds, are the largest European-descended groups in Africa today. In the nineteenth century, a second phase of colonisation brought a large number of French and British settlers to Africa. The Portuguese settled mainly in Angola, but also in Mozambique. The French settled in large numbers in Algeria where they became known collectively as pieds-noirs, and on a smaller scale in other areas of North and West Africa as well as in Madagascar. The British settled chiefly in South Africa as well as the colony of Rhodesia, and in the highlands of what is now Kenya. Germans settled in what is now Tanzania and Namibia, and there is still a population of German-speaking white Namibians. Smaller numbers of European soldiers, businessmen, and officials also established themselves in administrative centers such as Nairobi and Dakar. Decolonisation during the 1960s often resulted in the mass emigration of European-descended settlers out of Africa – especially from Algeria, Angola, Kenya and Rhodesia. However, in South Africa and Namibia, the white minority remained politically dominant after independence from Europe, and a significant population of Europeans remained in these two countries even after democracy was finally instituted at the end of the Cold War. South Africa has also become the preferred destination of white Anglo-Zimbabweans, and of migrants from all over southern Africa.

    European colonisation also brought sizeable groups of Asians, particularly people from the Indian subcontinent, to British colonies. Large Indian communities are found in South Africa, and smaller ones are present in Kenya, Tanzania, and some other southern and East African countries. The large Indian community in Uganda was expelled by the dictator Idi Amin in 1972, though many have since returned. The islands in the Indian Ocean are also populated primarily by people of Asian origin, often mixed with Africans and Europeans. The Malagasy people of Madagascar are a Austronesian people, but those along the coast are generally mixed with Bantu, Arab, Indian and European origins. Malay and Indian ancestries are also important components in the group of people known in South Africa as Cape Coloureds (people with origins in two or more races and continents).

    By most estimates, Africa contains well over a thousand languages (some have estimated over two thousand), most of African origin and a few of European origin. Africa is the most polyglot continent in the world; it is not rare to find individuals there who fluently speak not only several African languages, but one or two European ones as well. There are four major language families native to Africa.

    * The Afro-Asiatic languages are a language family of about 240 languages and 285 million people widespread throughout East Africa, North Africa, the Sahel, and Southwest Asia.
    * The Nilo-Saharan language family consists of more than a hundred languages spoken by 30 million people. Nilo-Saharan languages are mainly spoken in Chad, Ethiopia, Kenya, Sudan, Uganda, and northern Tanzania.
    * The Niger-Congo language family covers much of Sub-Saharan Africa and is probably the largest language family in the world in terms of different languages. A substantial number of them are the Bantu languages spoken in much of sub-Saharan Africa.
    * The Khoisan languages number about fifty and are spoken in Southern Africa by approximately 120,000 people. Many of the Khoisan languages are endangered. The Khoi and San peoples are considered the original inhabitants of this part of Africa.

    Following colonialism, nearly all African countries adopted official languages that originated outside the continent, although several countries nowadays also use various languages of native origin (such as Swahili) as their official language. In numerous countries, English and French (see African French) are used for communication in the public sphere such as government, commerce, education and the media. Arabic, Portuguese, Afrikaans and Malagasy are other examples of originally non-African languages that are used by millions of Africans today, both in the public and private spheres.

    Map showing the distribution of African language families and some major African languages. Afro-Asiatic extends from the Sahel to Southwest Asia. Niger-Congo is divided to show the size of the Bantu sub-family.


  5. #5
    Gforum Veterano
    Data de Ingresso
    Apr 2007

    Padrão North America

    North America is a continent in the Earth's northern hemisphere and (chiefly) western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the south and west by the North Pacific Ocean; South America lies to the southeast. It covers an area of about 24,709,000 square kilometers (9,540,000 sq mi), about 4.8% of the planet's surface or about 16.5% of its land area. As of July 2007, its population was estimated at nearly 524 million people. It is the third-largest continent in area, following Asia and Africa, and is fourth in population after Asia, Africa, and Europe. North America and South America are collectively known as the Americas.

    North America Location

    North and South America are popularly accepted as having been named after Italian explorer Amerigo Vespucci by the German cartographer Martin Waldseemüller. Vespucci was the first European to suggest that the Americas were not the East Indies, but a different landmass previously undiscovered by Europeans. Vespucci was the first to discover South America and the Amerique mountains of Central America, which connected his discoveries to those of Christopher Columbus. The etymology is further complicated by the need of cartographers to come up with a name that paralleled the feminine names of the other continents (e.g. Europa, Asia etc.). The convention is to use the surname for naming discoveries except in the case of royalty and so a derivation from "Amerigo Vespucci" may be problematic.

    The second and less generally accepted theory is that the continents are named after an English merchant named Richard Amerike from Bristol, who is believed to have financed John Cabot's voyage of discovery from England to Newfoundland in 1497. A minutely explored belief that has been advanced is that America was named for a Spanish sailor bearing the ancient Visigothic name of 'Amairick'. Another is that the name is rooted in an Native American language.

    Scientists have several theories as to the origins of the early human population of North America. The indigenous peoples of North America themselves have many creation stories, by which they assert that they have been present on the land since its creation.

    Before contact with Europeans, the natives of North America were divided into many different polities, from small bands of a few families to large empires. They lived in several "culture areas", which roughly correspond to geographic and biological zones and give a good indication of the main lifeway or occupation of the people who lived there (e.g. the Bison hunters of the Great Plains, or the farmers of Mesoamerica). Native groups can also be classified by their language family (e.g. Athapascan or Uto-Aztecan). It is important to note that peoples with similar languages did not always share the same material culture, nor were they always allies.

    Scientists believe that the Inuit people of the high Arctic came to North America much later than other native groups, as evidenced by the disappearance of Dorset culture artifacts from the archaeological record, and their replacement by the Thule people.

    The ruins of Chichen Itza.

    During the thousands of years of native inhabitation on the continent, cultures changed and shifted. Archaeologists often name different cultural groups they discover after the site where they are first found. One of the oldest cultures yet found is the Clovis culture of modern New Mexico. A more recent example is the group of related cultures called the Mound builders (e.g. the Fort Walton Culture), found in the Mississippi river valley. They flourished from 3000 BC to the 1500s AD.

    The more southern cultural groups of North America were responsible for the domestication of many common crops now used around the world, such as tomatoes and squash. Perhaps most importantly they domesticated one of the world's major staples, maize (corn).

    As a result of the development of agriculture in the south, many important cultural advances were made there. For example, the Maya civilization developed a writing system, built huge pyramids, had a complex calendar, and developed the concept of zero around 400 CE, a few hundred years after the Mesopotamians. The Mayan culture was still present when the Spanish arrived in Central America, but political dominance in the area had shifted to the Aztec Empire further north.

    Upon the arrival of the Europeans in the "New World", native peoples found their culture changed drastically. As such, their affiliation with political and cultural groups changed as well, several linguistic groups went extinct, and others changed quite quickly. The names and cultures that Europeans recorded for the natives were not necessarily the same as the ones they had used a few generations before, or the ones in use today.

    North America occupies the northern portion of the landmass generally referred to as the New World, the Western Hemisphere, the Americas, or simply America (which is sometimes considered a single continent and North America a subcontinent). North America's only land connection is to South America at the Colombia-Panama border according to most authorities, or at the Panama Canal by some and even at the Isthmus of Tehuantepec, Mexico by a few who separate Central America which rests mostly on the Caribbean Plate. Before the Central American isthmus was raised, the region had been underwater. The islands of the West Indies delineate a submerged former land bridge, which had connected North America and South America via Florida and Venezuela.

    The continental coastline is long and irregular. The Gulf of Mexico is the largest body of water indenting the continent, followed by Hudson Bay. Others include the Gulf of Saint Lawrence and the Gulf of California.

    There are numerous islands off the continent’s coasts: principally, the Arctic Archipelago, the Greater and Lesser Antilles, the Alexander Archipelago, and the Aleutian Islands. Greenland, a Danish self-governing island and the world's largest, is on the same tectonic plate (the North American Plate) and is part of North America geographically. Bermuda is not part of the Americas, but is an oceanic island which was formed on the fissure of the Mid-Atlantic Ridge over 100 million years ago. The nearest landmass to it is Cape Hatteras, North Carolina, and it is often thought of as part of North America, especially given its historical, political and cultural ties to Virginia and other parts of the continent.

    A satellite composite image of North America

    The vast majority of North America is on the North American Plate. Parts of California and western Mexico form the partial edge of the Pacific Plate, with the two plates meeting along the San Andreas fault. The southern-most portion of the continent and much of the West Indies lie on the Caribbean Plate, while the Juan de Fuca and Cocos Plates border the North American Plate on its western frontier.

    The continent can be divided into four great regions (each of which contains many sub-regions): the Great Plains stretching from the Gulf of Mexico to the Canadian Arctic; the geologically young, mountainous west, including the Rocky Mountains, the Great Basin, California and Alaska; the raised but relatively flat plateau of the Canadian Shield in the northeast; and the varied eastern region, which includes the Appalachian Mountains, the coastal plain along the Atlantic seaboard, and the Florida peninsula. Mexico, with its long plateaus and cordilleras, falls largely in the western region, although the eastern coastal plain does extend south along the Gulf.

    The western mountains are split in the middle, into the main range of the Rockies and the coast ranges in California, Oregon, Washington, and British Columbia with the Great Basin—a lower area containing smaller ranges and low-lying deserts—in between. The highest peak is Denali in Alaska.

    The United States Geographical Survey states that the geographic center of North America is "6 miles west of Balta, Pierce County, North Dakota" at approximately 48°10′N 100°10′W / 48.167, -100.167, approximately 15 miles (25 km) from Rugby, North Dakota. The USGS further states that “No marked or monumented point has been established by any government agency as the geographic center of either the 50 States, the conterminous United States, or the North American continent.” Nonetheless, there is a 15-foot (4.5 m) field stone obelisk in Rugby claiming to mark the center.

    The prevalent languages in North America are English, Spanish, and French. The term Anglo-America is used to refer to the anglophone countries of the Americas: namely Canada (where English and French are co-official) and the United States, but also sometimes Belize and parts of the Caribbean. Latin America refers to the other areas of the Americas (generally south of the United States) where Romance languages derived from Latin predominate: the other republics of Central America, Mexico, much of the Caribbean, and most of South America.

    The French language has historically played a significant role in North America and retains a distinctive presence in some regions. Canada is officially bilingual; French is the official language of the Canadian province of Quebec and is co-official with English in the province of New Brunswick. Other French-speaking locales include the French West Indies and Saint-Pierre and Miquelon, as well as the U.S. state of Louisiana, where French is also an official language. Haiti is included with this group based on past historical association but Haitians speak Creole and French.

    Socially and culturally, North America presents a well-defined entity. Canada and the United States have a similar culture and similar traditions as a result of both countries being former British colonies. A common cultural and economic market has developed between the two nations because of the strong economic and historical ties. Spanish-speaking North America shares a common past as former Spanish colonies. In Mexico and the Central American countries where civilizations like the Maya developed, indigenous people preserve traditions across modern boundaries. Central American and Spanish-speaking Caribbean nations have historically had more in common due to geographical proximity and the fact that, after winning independence from Spain, Mexico never took part in an effort to build a Central American Union.

    Economically, Canada and the United States are the wealthiest and most developed nations in the continent, followed by Mexico, a newly industrialized country; the countries of Central America and the Caribbean are much less developed. The most important trade blocs are the Caribbean Community and Common Market (CARICOM), the North American Free Trade Agreement (NAFTA), and the recently signed Central American Free Trade Agreement (CAFTA)—the last of these being an example of the economic integration sought by the nations of this subregion as a way to improve their financial status.

    Demographically, North America is a racially and ethnically diverse continent. Its three main ethnic groups are Whites, Mestizos and Blacks (chiefly African-Americans and Afro-Caribbeans).[citation needed] There is a significant minority of Amerindians and Asians among other less numerous groups.

    Countries and territories

    North America is often divided into subregions but no universally accepted divisions exist. Central America comprises the southern region of the continent, but its northern terminus varies between sources. Geophysically, the region starts at the Isthmus of Tehuantepec in Mexico (namely the Mexican states of Campeche, Chiapas, Tabasco, Quintana Roo, and Yucatán). The United Nations geoscheme includes Mexico in Central America; conversely, the European Union excludes both Mexico and Belize from the area. Geopolitically, Mexico is frequently not considered a part of Central America.

    Northern America is used to refer to the northern countries and territories of North America: Canada, the United States, Greenland, Bermuda, and St. Pierre and Miquelon. They are often considered distinct from the southern portion of the Americas, which largely comprise Latin America. The term Middle America is sometimes used to collectively refer to Mexico, the nations of Central America, and the Caribbean.

    Mexico City is the most populous city in North America

    New York City, the largest city in the United States and a major world city

    Toronto is the most populous city in Canada -- fifth in North America -- and is one of the world's most ethnically diverse cities.


  6. #6
    Gforum Veterano
    Data de Ingresso
    Apr 2007

    Padrão South America

    South America is a continent occupying the southern part of the supercontinent of America. It sits entirely in the Western Hemisphere, and mostly in the Southern Hemisphere with a small portion in the Northern Hemisphere. It is bordered on the west by the Pacific Ocean and on the north and east by the Atlantic Ocean. North America and the Caribbean Sea lie to the northwest.

    South America was named in 1507 by cartographers Martin Waldseemüller and Matthias Ringmann after Amerigo Vespucci, who was the first European to suggest that the Americas were not the East Indies, but a New World unknown to Europeans.
    South America has an area of 17,780,000 square kilometers (6,890,000 sq mi), or almost 3.5% of the Earth's surface. As of 2005, its population was estimated at more than 371,090,000. South America ranks fourth in area (after Asia, Africa, and North America) and fifth in population (after Asia, Africa, Europe, and North America).

    South America Location

    South America occupies the major southern portion of the landmass generally referred to as the New World, the Western Hemisphere, the Americas, or simply America (which is sometimes considered a single continent and South America a subcontinent). It is south and east of the Colombia-Panama border according to most authorities or, according to a few, the Panama Canal which transects the Isthmus of Panama. Almost all of mainland South America sits on the South American Plate. Geopolitically and geographically, all of Panama – including the segment east of the Panama Canal in the isthmus – is generally considered a part of North America alone and among the countries of Central America.

    Many of the islands of the Caribbean (or West Indies) – e.g., the Leeward and Lesser Antilles – sit atop the Caribbean Plate, a tectonic plate with a diffuse topography. The islands of Aruba, Barbados, Trinidad, and Tobago sit on the northerly South American continental shelf. The Netherlands Antilles and the federal dependencies of Venezuela lie along the northerly South American. Geopolitically, the island states and overseas territories of the Caribbean are generally grouped as a part or subregion of North America. The South American nations that border the Caribbean Sea – including Colombia, Venezuela, Guyana, Suriname, and French Guiana – are also known as Caribbean South America. Other islands are the Galápagos, Easter Island (in Oceania but belongs to Chile), Robinson Crusoe Island, Chiloé Island, and the Tierra del Fuego

    A composite relief image of South America.

    South America is home to the world's highest waterfall, Angel Falls in Venezuela, the largest river (by volume), the Amazon River, the longest mountain range, the Andes (whose highest mountain is Aconcagua at 6,962 m (22,841 ft)), the driest desert, the Atacama Desert, the largest rainforest, the Amazon Rainforest, the highest capital city, La Paz, Bolivia, the highest commercially navigable lake in the world, Lake Titicaca, and the world's southernmost town, Puerto Toro, Chile.

    South America's major mineral resources are gold, silver, copper, iron ore, tin, and oil. The many resources of South America have brought high income to its countries especially in times of war or of rapid economic growth by industrialized countries elsewhere. However, the concentration in producing one major export commodity often has hindered the development of diversified economies. The inevitable fluctuation in the price of commodities in the international markets has led historically to major highs and lows in the economies of South American states, often also causing extreme political instability. This is leading to efforts to diversify their production to drive them away from staying as economies dedicated to one major export.

    South America is home to many interesting and unique species of animals including the llama, anaconda, piranha, jaguar, vicuña, and tapir. The Amazon rainforests possess high biodiversity, containing a major proportion of the Earth's species.

    The largest country in South America by far, in both area and population, is Brazil, followed by Argentina. Regions in South America include the Andean States, the Guianas, the Southern Cone, and Brazil.

    The Andes

    River in the Amazon rainforest

    The rise of agriculture and domestication of animals

    A pair of alpacas near an Inca burial site in Peru

    South America is thought to have been first inhabited by people crossing the Bering Land Bridge, which is now the Bering Strait. Some archaeological finds do not fit this theory, and have led to an alternative theory Pre-Siberian American Aborigines. The first evidence for the existence of agricultural practices in South America date back to circa 6500 BC, when potatoes, chillies and beans began to be cultivated for food in the highlands of the Amazon Basin. Pottery evidence further suggests that manioc, which remains a staple foodstuff today, was being cultivated as early as 2000 BC.

    By 2000 BC many agrarian village communities had been settled throughout the Andes and the surrounding religious regions. Fishing became a widespread practice along the coast which helped to establish fish as a primary source of food. Irrigation systems were also developed at this time, which aided in the rise of an agrarian society.

    South Americans cultures began domesticating llamas, vicuñas, guanacos, and alpacas in the highlands of the Andes circa 3500 BC. Besides their use as sources of meat, and wool, these animals were used for transportation of goods (maximum load for a llama is typically 40 kg).

    he rise of agriculture and the subsequent appearance of permanent human settlements allowed for the multiple and overlapping beginnings of civilizations in South America.

    The earliest known settlements, and culture in South America, and the Americas altogether, are the Valdivia on the south east coast of Ecuador.

    The earliest known South American civilization was at Norte Chico, on the central Peruvian coast. Though a pre-ceramic culture, the monumental architecture of Norte Chico is contemporaneous with the pyramids of Ancient Egypt. The Chavín established a trade network and developed agriculture by 900 BC, according to some estimates and archaeological finds. Artifacts were found at a site called Chavín de Huantar in modern Peru at an elevation of 3,177 meters. Chavín civilization spanned 900 BC to 300 BC.

    The Muisca were the main indigenous civilization in what is now modern Colombia. They established a confederation of many clans, or cacicazgos, that had a free trade network among themselves. They were goldsmiths and farmers.

    Other important Pre-Columbian cultures include: Moche (100 BC – 700 AD, at the northern coast of Peru); Tiuahuanaco or Tiwanaku (100 BC – 1200 AD, Bolivia); the Cañaris (in south central Ecuador), Paracas and Nazca (400 BC – 800 AD, Peru); Wari or Huari Empire (600 – 1200, Central and northern Peru); Chimu Empire (1300 – 1470, Peruvian northern coast); Chachapoyas; and the Aymaran kingdoms (1000 – 1450, Bolivia and southern Peru).

    Holding their capital at the great cougar-shaped city of Cusco, the Inca civilization dominated the Andes region from 1438 to 1533. Known as Tawantin suyu, or "the land of the four regions," in Quechua, the Inca civilization was highly distinct and developed. Inca rule extended to nearly a hundred linguistic or ethnic communities, some 9 to 14 million people connected by a 25,000 kilometer road system. Cities were built with precise, unmatched stonework, constructed over many levels of mountain terrain. Terrace farming was a useful form of agriculture. There is evidence of excellent metalwork and even successful brain surgery in Inca civilization

    The Inca ruins of Machu Picchu

    Culture and language
    Brazil is the only Portuguese-speaking nation in the Americas, making the language an important part of Brazilian national identity.
    Brazil is the only Portuguese-speaking nation in the Americas, making the language an important part of Brazilian national identity.

    Portuguese and Spanish are the most spoken languages in South America, each spoken by around 90% of the continent's population. Portuguese is the official language of Brazil, which holds nearly 50% of the South American population. Spanish is the official language of most countries of the continent. Dutch is the official language of Suriname; English is the official language of Guyana, although there are at least twelve other languages spoken in the country such as Hindi, Arabic, and various indigenous dialects. English is also spoken in the Falkland Islands. French is the official language of French Guiana.

    Indigenous languages of South America include, among several others, Quechua in Ecuador, Peru, and Bolivia; Guaraní in Paraguay and, to a much less extent, in Bolivia; Aymara in Bolivia, Peru and less often in Chile, while Mapudungun is spoken in certain pockets of southern Chile and, more rarely, Argentina. At least three South American indigenous languages (Quechua in Ecuador,Peru and Bolivia, Aymara also in Bolivia, and guarani in Paraguay) are recognized along with Spanish as national languages.

    Other languages found in South America include Hindi and Indonesian in Suriname; Italian in Argentina, Brazil, Peru, Uruguay, Venezuela, and Chile; and German in certain pockets, Argentina, Chile, Venezuela, Peru and Paraguay and in many regions of the southern states of Brazil (Riograndenser Hunsrückisch is the most widely spoken German dialect in the country; among other Germanic dialects, a Brazilian form of Pomeranian is also well represented and is experiencing a revival). Welsh remains spoken and written in the historic towns of Trelew and Rawson in the Argentinean Patagonia. There are also small clusters of Japanese-speakers in Brazil, Bolivia, Colombia, Paraguay, Peru and Ecuador. Arabic speakers, often of Lebanese, Syrian or Palestinian descent, can be found in Arab communities in Brazil, Ecuador, Chile, Argentina, and less frequently in Colombia and Paraguay.

    European Control over South America since 1700
    In most of the continent's countries, the upper classes and well-educated people regularly study English, French, German or Italian. In those areas where tourism is a significant industry, English and some other European languages are often spoken. There are small Spanish speaking areas in Southernmost Brazil, due to the proximity of Uruguay.

    South Americans are culturally enriched by the historic connection with Europe, especially Spain and Portugal, and the impact of mass culture from the United States of America.

    View of a financial district in São Paulo, Brazil

    Buenos Aires - Argentina

    South American nations have a rich variety of music. Some of the most famous genres include cumbia from Colombia, samba and bossa nova from Brazil, and tango from Argentina and Uruguay. Also well known is the non-commercial folk genre Nueva Canción movement which was founded in Argentina and Chile and quickly spread to the rest of the Latin America. People on the Peruvian coast created the fine guitar and cajon duos or trios in the most mestizo (mixed) of South American rhythms such as the Marinera (from Lima), the Tondero (from Piura), the 19th century popular Creole Valse or Peruvian Valse, the soulful Arequipan Yaravi and the early 20th century Paraguayan Guarania. In the late 20th century, Rock en Español emerged by young hipsters influenced by British pop and American rock in Argentina, Chile, Colombia, Peru and Uruguay. Brazil has a Portuguese-language pop rock industry as well a great variety of other music genres.

    The literature of South America has attracted considerable critical and popular acclaim, especially with the Latin American Boom of the 1960s and 1970s, and the rise of authors such as Gabriel García Márquez in novels, and Pablo Neruda and Jorge Luis Borges in other genres.

    Santiago, Chile financial center at night

    View of a financial center in Bogotá, Colombia.

    Lima, Peru financial center

    Because of South America's broad ethnic mix, South American cuisine takes on African, American Indian, Asian and European influences. Bahia, Brazil, is especially well-known for its West African-influenced cuisine. Argentines, Chileans and Uruguayans regularly consume wine, while Argentina along with Paraguay, Uruguay and people in southern Chile and Brazil enjoy a sip of Mate a regional brewed herb cultivated for its drink, the paraguayan version, Terere, differing from the others in that it's served cold. Pisco is a liquor distilled from grapevine produced in Peru and Chile, however, there is a recurring dispute between those countries regarding its origins. Peruvian cuisine mixes elements from Chinese, Japanese, Spanish, African, Andean and Amazonic food.

    Brazil is the only Portuguese-speaking nation in the Americas, making the language an important part of Brazilian national identity.


    Descendents of Indigenous peoples, such as the Quechua and Aymara, make up the majority of the population in Peru and Bolivia, and are a significant element in most other former Spanish colonies. Exceptions to this include Argentina and Uruguay where Southern European descent make up the majority of the population. Mestizo (mixed white and amerindian) are the largest ethnic group in Chile, Paraguay, Venezuela, Colombia and Ecuador. Suriname is the only country in South America where Asians form the majority of the population. Creoles are the largest ethnic group in French Guiana but they also form a large part of the population in Guyana, Venezuela, Suriname, Colombia, Peru and Ecuador. Brazil is the South American country with the biggest ethnic diversity, with large numbers of Blacks, Whites and mulattoes, and also with significant number of Asians and Amerindians.

    Indigenous peoples

    * Alacalufe
    * Atacameños
    * Aymara
    * Awá
    * Banawa
    * Cañaris
    * Caiapos
    * Chibcha
    * Cocama
    * Diaguitas
    * Chayahuita
    * Enxet
    * Gê
    * Guaraní

    * Juris
    * Mapuche
    * Matsés
    * Pehuenche
    * Quechuas
    * Shipibo
    * Shuar
    * Tupi
    * Xucuru
    * Urarina
    * Yagua
    * Yąnomamö
    * Zaparos

    * Arawaks
    * Wai Wai

    Última edição por Freundlich; 11-05-2008 às 10:00.

  7. #7
    Gforum Veterano
    Data de Ingresso
    Apr 2007

    Padrão Europe

    Europe is one of the seven traditional continents of Earth. The westernmost peninsula of Eurasia, it is bounded to the north by the Arctic Ocean, to the west by the Atlantic Ocean, to the south by the Mediterranean Sea, to the southeast by the Caucasus Mountains, the Black Sea and the waterways connecting the Black Sea to the Mediterranean. To the east, Europe is generally divided from Asia by the water divide of the Ural Mountains, the Ural River, and by the Caspian Sea.

    Europe Location

    Europe is the world's second-smallest continent in terms of area, covering about 10,180,000 square kilometres (3,930,000 sq mi) or 2% of the Earth's surface. It hosts a large number of sovereign states (ca. 50), whose precise amount depends on the underlying definition of Europe's border, as well as on the in- or exclusion of semi-recognized states. Of all European countries, Russia is the largest by both area and population, while the Vatican is the smallest. Europe is the third most populous continent after Asia and Africa with a population of 710,000,000 or about 11% of the world's population. However, Europe's borders and population are in dispute, as the term continent can refer to a cultural and political distinction or a physiographic one.

    The term "Europe" has multiple uses. Its principal ones are geographical and political.

    * Physiographically, Europe is the westernmost peninsula of the continent of Eurasia; its limits are well defined by sea to the North, South and West, and by a slightly arbitrary boundary discussed below on the east and south-eastern side. The Ural mountains are usually taken as the eastern limit of Europe; points beyond are not usually considered to be part of the continent.

    * Politically, Europe comprises those countries in the European Union, but may at times be used more casually to refer to both the EU together with other non-EU countries in the same general region.

    In addition, people in countries such as Ireland, United Kingdom, Scandinavia and the North Atlantic and Mediterranean islands, may routinely refer to "continental" or "mainland" Europe (or simply "the Continent"), as a term for the main land mass.

    In ancient Greek mythology, Europa was a Phoenician princess whom Zeus abducted after assuming the form of a dazzling white bull. He took her to the island of Crete where she gave birth to Minos, Rhadamanthus and Sarpedon. For Homer, Europe (Greek: Εὐρώπη, Eurṓpē; see also List of traditional Greek place names) was a mythological queen of Crete, not a geographical designation. Later Europa stood for mainland Greece, and by 500 BC its meaning had been extended to lands to the north.

    Etymologically, the dominant theory suggests the name Europe is derived from the Greek roots meaning broad (eur-) and eye (op-, opt-), hence Eurṓpē, "wide-gazing" (compare with glaukōpis (grey-eyed) Athena or boōpis (ox-eyed) Hera). Broad has been an epithet of Earth itself in the reconstructed Proto-Indo-European religion. A minority, however, suggest this Greek popular etymology is really based on a Semitic word such as the Akkadian erebu meaning "to go down, set",cognate to Phoenician 'ereb "evening; west" and Arabic Maghreb, Hebrew ma'ariv. See also Erebus, PIE *h1regwos, "darkness".

    Most major world languages use words derived from "Europa" to refer to the continent. Chinese, for example uses the word Ōuzhōu (歐洲), which is an abbreviation of the transliterated name Ōuluóbā zhōu (歐羅巴洲). However, the Turkish people used the term Frengistan (land of the Franks) in referring to Europe.

    Europe is the northwestern constituent of the larger landmass known as Eurasia, or Afro-Eurasia: Asia occupies the eastern bulk of this continuous landmass and all share a common continental shelf. Europe's eastern frontier is now commonly delineated by the Ural Mountains in Russia. The first century AD geographer Strabo, took the Tanais River to be the boundary, as did early Judaic sources. The southeast boundary with Asia is not universally defined. Most commonly the Ural or, alternatively, the Emba River serve as possible boundaries. The boundary continues to the Caspian Sea, the crest of the Caucasus Mountains or, alternatively, the Kura River in the Caucasus, and on to the Black Sea; the Bosporus, the Sea of Marmara, and the Dardanelles conclude the Asian boundary. The Mediterranean Sea to the south separates Europe from Africa. The western boundary is the Atlantic Ocean; Iceland, though nearer to Greenland (North America) than mainland Europe, is generally included in Europe. There is ongoing debate on where the geographical centre of Europe is. For detailed description of the boundary between Asia and Europe see transcontinental nation.

    Land relief in Europe shows great variation within relatively small areas. The southern regions, however, are more mountainous, while moving north the terrain descends from the high Alps, Pyrenees and Carpathians, through hilly uplands, into broad, low northern plains, which are vast in the east. This extended lowland is known as the Great European Plain, and at its heart lies the North German Plain. An arc of uplands also exists along the north-western seaboard, which begins in the western parts of the islands of Britain and Ireland, and then continues along the mountainous, fjord-cut, spine of Norway.

    This description is simplified. Sub-regions such as the Iberian Peninsula and the Italian Peninsula contain their own complex features, as does mainland Central Europe itself, where the relief contains many plateaus, river valleys and basins that complicate the general trend. Sub-regions like Iceland, Britain and Ireland are special cases. The former is a land unto itself in the northern ocean which is counted as part of Europe, while the latter are upland areas that were once joined to the mainland until rising sea levels cut them off.


    Biomes of europe

    Europe lies mainly in the temperate climate zones, being subjected to prevailing westerlies.

    The climate is milder in comparison to other areas of the same latitude around the globe. This is due to the Gulf Stream. The Gulf Stream is nicknamed "Europe's central heating", because it makes Europe's climate warmer and wetter than it would otherwise be. The Gulf Stream does not only carry warm water to Europe's coast but also warms up the prevailing westerly winds that blow across the continent from the Atlantic Ocean.

    Therefore the average temperature throughout the year of Naples is 16 °C (60.8 °F), while it is only 12 °C (53.6 °F) in New York City which is almost on the same latitude. Berlin, Germany; Calgary, Canada; and Irkutsk, in the Asian part of Russia, lie at about the same latitude. But January temperatures in Berlin average about 8 °C (15 °F) higher than those in Calgary, and they are almost 22 °C (40 °F) higher than the average temperatures in Irkutsk.


    Biogeographic regions of Europe (including Asian part of Turkey)

    Having lived side-by-side with agricultural peoples for millennia, Europe's animals and plants have been profoundly affected by the presence and activities of man. With the exception of Fennoscandia and northern Russia, few areas of untouched wilderness are currently found in Europe, except for various national parks.

    The main natural vegetation cover in Europe is mixed forest. The conditions for growth are very favourable. In the north, the Gulf Stream and North Atlantic Drift warm the continent. Southern Europe could be described as having a warm, but mild climate. There are frequent summer droughts in this region. Mountain ridges also affect the conditions. Some of these (Alps, Pyrenees) are oriented east-west and allow the wind to carry large masses of water from the ocean in the interior. Others are oriented south-north (Scandinavian Mountains, Dinarides, Carpathians, Apennines) and because the rain falls primarily on the side of mountains that is oriented towards sea, forests grow well on this side, while on the other side, the conditions are much less favourable. Few corners of mainland Europe have not been grazed by livestock at some point in time, and the cutting down of the pre-agricultural forest habitat caused disruption to the original plant and animal ecosystems.

    In temperate Europe, mixed forest with both broadleaf and coniferous trees dominate. The most important species in central and western Europe are beech and oak. In the north, the taiga is a mixed spruce-pine-birch forest; further north within Russia and extreme northern Scandinavia, the taiga gives way to tundra as the Arctic is approached. In the Mediterranean, many olive trees have been planted, which are very well adapted to its arid climate; Mediterranean Cypress is also widely planted in southern Europe. The semi-arid Mediterranean region hosts much scrub forest. A narrow east-west tongue of Eurasian grassland (the steppe) extends eastwards from Ukraine and southern Russia and ends in Hungary and traverses into taiga to the north.

    Glaciation during the most recent ice age and the presence of man affected the distribution of European fauna. As for the animals, in many parts of Europe most large animals and top predator species have been hunted to extinction. The woolly mammoth was extinct before the end of the Neolithic period. Today wolves (carnivores) and bears (omnivores) are endangered. Once they were found in most parts of Europe. However, deforestation and hunting caused these animals to withdraw further and further. By the Middle Ages the bears' habitats were limited to more or less inaccessible mountains with sufficient forest cover. Today, the brown bear lives primarily in the Balkan peninsula, Scandinavia, and Russia; a small number also persist in other countries across Europe (Austria, Pyrenees etc.), but in these areas brown bear populations are fragmented and marginalised because of the destruction of their habitat. In addition, polar bears may be found on Svalbard, a Norwegian archipelago far north of Scandinavia. The wolf, the second largest predator in Europe after the brown bear, can be found primarily in Eastern Europe and in the Balkans, with a handful of packs in pockets of Western Europe (Scandinavia, Spain, etc.).

    Other important European carnivores are Eurasian lynx, European wild cat, foxes (especially the red fox), jackal and different species of martens, hedgehogs, different species of reptiles (like snakes as (vipers and grass snakes) and amphibians, different birds (owls, hawks and other birds of prey).

    Important European herbivores are snails, larvae, fish, different birds, and mammals, like rodents, deer and roe deer, boars, and living in the mountains, marmots, steinbocks, chamois among others.

    Sea creatures are also an important part of European flora and fauna. The sea flora is mainly phytoplankton. Important animals that live in European seas are zooplankton, molluscs, echinoderms, different crustaceans, squids and octopuses, fish, dolphins, and whales.

    Biodiversity is protected in Europe through the Council of Europe's Bern Convention), which has also been signed by the European Community as well as non-European states.


    Since the Renaissance, Europe has had a major influence in culture, economics and social movements in the world. European demographics are important not only historically, but also in understanding current international relations and population issues.

    Some current and past issues in European demographics have included religious emigration, race relations, economic immigration, a declining birth rate and an aging population. In some countries, such as Ireland and Poland, access to abortion is currently limited; in the past, such restrictions and also restrictions on artificial birth control were commonplace throughout Europe. Furthermore, three European countries (The Netherlands, Belgium and Switzerland) have allowed a limited form of voluntary euthanasia for some terminally ill people.

    In 2005 the population of Europe was estimated to be 728 million according to the United Nations, which is slightly more than one-ninth of the world's population. A century ago Europe had nearly a quarter of the world's population. The population of Europe has grown in the past century, but in other areas of the world (in particular Africa and Asia) the population has grown far more quickly.[89] According to UN population projection (medium variant), Europe's share will fall to 7% in 2050, numbering 653 million. Within this context, significant disparities exist between religions in relation to fertility rates. The average number of children per female of child bearing age is 1.52. According to some sources,[92][93] this rate is higher among Muslims. In 2005 the EU had an overall net gain from immigration of 1.8 million people, despite having one of the highest population densities in the world. This accounted for almost 85% of Europe's total population growth.

    Modern Political map

    The prevalent religions of Europe are the following:

    * Christianity
    o Roman Catholicism: Countries or areas with significant Catholic populations are Andorra, Austria, west Belarus, Belgium, Bosnia and Herzegovina, Croatia, the Czech Republic, France, south and west Germany, Hungary, Ireland, Italy, Latgale region in Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Monaco, south Netherlands, Poland, Portugal, Romania, San Marino, Slovakia, Slovenia, Spain, central and south Switzerland, west Ukraine, and Vatican City. There are also large Catholic minorities in the United Kingdom (especially in Northern Ireland), and most European countries. In Serbia Catholics are a small minority.
    o Eastern-Rite Catholicism also known as "Uniatism", is found in western Ukraine, Bulgaria, Cyprus, Greece, Armenia, Hungary, the Republic of Macedonia, Romania, Russia, Serbia and Slovakia, southern Italy (Sardinia and Sicily) and Corsica, France.
    o Orthodox Christianity: The countries with significant Orthodox populations are Armenia, Belarus, Bosnia and Herzegovina, Bulgaria, Cyprus, Georgia, Greece, the Republic of Macedonia, Moldova, Montenegro, Romania, Russia, Serbia, Ukraine, easternmost Hungary, a small minority in Southern Italy, Kazakhstan, sizable minorities in Albania, Latvia and Lithuania, small minority in Poland, Finland (Karelia).
    o Protestantism: Countries with significant Protestant populations include Denmark, Estonia, Finland, north and east Germany, Iceland, Latvia, the Netherlands, Norway, Sweden; east, north and west Switzerland; and the United Kingdom. There are significant minorities in France, the northwestern Piedmont region of Italy, Slovakia, the Czech Republic, Hungary, and a small minority in Poland.
    * Islam: Countries with significant Muslim population are Albania, Azerbaijan, Bosnia and Herzegovina, Bulgaria, Georgia, Kazakhstan, Montenegro, several republics of Russia, Serbia, Turkey, Crimea in Ukraine, and, from Western Europe, France and the United Kingdom mainly among the one million strong Pakistani community.[105]

    Other religions are practiced by smaller groups in Europe, including:

    * Judaism primarily in France, Germany, the United Kingdom, Russia and Italy. At one time Judaism was practiced widely throughout the European continent, though it has dwindled in numbers since the expulsion, extermination, and exodus of Jews during the later portion of the second millennium.
    * Hinduism mainly among Indian immigrants in the United Kingdom. In 1998 there were an estimated 1,382,000 Hindu adherents in Europe alone.[106]
    * Buddhism thinly spread throughout Europe and growing rapidly in recent years, about 3 million.[107][108]
    * Indigenous European pagan traditions and beliefs, many countries (a fast-growing neopagan movement in France, Germany, Ireland and the United Kingdom is noted), and one neopagan faith Asatru recognized as a minority religion in Iceland (since 1973), Norway and Sweden.
    * Rastafari, communities in the United Kingdom, France, Spain, Portugal, Italy and elsewhere.
    * Sikhism, nearly 1 million adherents of Sikhism in Europe. Most of the community live in United Kingdom (750,000) & Italy (70,000). Around 10,000 in Belgium & France. Netherlands and Germany have a Sikh population of 12,000. All other countries have less than or 5,000 Sikhs.
    * Jainism, small membership rolls, mainly among Indian immigrants in the United Kingdom.
    * Voodoo, mainly among black Caribbean and West African immigrants in the United Kingdom and France.
    * Traditional African Religions (including Muti), mainly in the United Kingdom and France.
    * Other religions with few (or under a million) adherents in Europe: Animism, Christian Scientists, Eco-religion, Gnosticism, Paganism, Jehovah's Witnesses, Mennonites, Moravian Church, Mormonism or Latter-day Saints, Pantheism, Polytheism, theological relativism, Scientology, Seventh-day Adventists, Universal Life Church, Unitarians, Wiccan, and Zoroastrianism.

    Millions of Europeans profess no religion or are atheist, agnostic or humanist. The largest non-confessional populations (as a percentage) are found in the Czech Republic, Denmark, France, Germany, the Netherlands, Norway, Sweden and the former soviet countries of Belarus, Estonia, Russia and Ukraine, although most former communist countries have significant non-confessional populations.

    Official religions

    A number of countries in Europe have official religions, including Liechtenstein, Malta, Monaco, the Vatican City (Catholic), Greece (Eastern Orthodox), Denmark, Iceland, and Norway (Lutheran). In Switzerland, some cantons are officially Catholic, others Reformed Protestant. Some Swiss villages even have their religion as well as the village name written on the signs at their entrances.

    Georgia has no established church, but the Georgian Orthodox Church enjoys de facto privileged status. In Finland, both the Finnish Orthodox Church and the Lutheran Church are official. England, a part of the UK, has Anglicanism as its official religion. Scotland, another part of the UK, has Presbyterianism as its national church, but it is no longer "official". In Sweden, the national church is Lutheranism, but it is also no longer "official". Azerbaijan, France, Portugal, Romania, Russia, Spain and Turkey are officially "secular".

    Predominant religions in Europe


  8. #8
    Gforum Veterano
    Data de Ingresso
    Apr 2007

    Padrão Antarctica

    Antarctica is Earth's southernmost continent, overlying the South Pole. It is situated in the southern hemisphere, almost entirely south of the Antarctic Circle, and is surrounded by the Southern Ocean. At 14.4 million km² (5.4 million sq mi), it is the fifth-largest continent in area after Asia, Africa, North America, and South America. Some 98% of Antarctica is covered by ice, which averages at least 1.6 kilometres (1.0 mi) in thickness.

    On average, Antarctica is the coldest, driest and windiest continent, and has the highest average elevation of all the continents. Since there is little precipitation, except at the coasts, the interior of the continent is technically the largest desert in the world. There are no permanent human residents and there is no evidence of any existing or pre-historic indigenous population. Only cold-adapted plants and animals survive there, including penguins, fur seals, mosses, lichen, and many types of algae.

    The name Antarctica is a romanized version of the Greek compound word Αntarktiké (Aνταρκτική), meaning "Opposite of the Arctic". Although myths and speculation about a Terra Australis ("Southern Land") date back to antiquity, the first confirmed sighting of the continent is commonly accepted to have occurred in 1820 by the Russian expedition of Mikhail Lazarev and Fabian Gottlieb von Bellingshausen. However, the continent remained largely neglected for the rest of the 19th century because of its hostile environment, lack of resources, and isolation.

    The Antarctic Treaty was signed in 1959 by twelve countries; to date, forty-five countries have signed the treaty. The treaty prohibits military activities and mineral mining, supports scientific research, and protects the continent's ecozone. Ongoing experiments are conducted by more than 4,000 scientists of many nationalities and with different research interests

    Antarctica Location

    Adelie Penguin chicks in Antarctica, with MS Explorer and an iceberg in the background. The image was taken in January 1999. MS Explorer sank on November 23, 2007, after hitting an iceberg in Antarctica.

    Belief in the existence of a Terra Australis—a vast continent in the far south of the globe to "balance" the northern lands of Europe, Asia and north Africa—had existed since the times of Ptolemy (1st century AD), who suggested the idea to preserve the symmetry of all known landmasses in the world. Depictions of a large southern landmass were common in maps such as the early 16th century Turkish Piri Reis map. Even in the late 17th century, after explorers had found that South America and Australia were not part of the fabled "Antarctica", geographers believed that the continent was much larger than its actual size.

    European maps continued to show this hypothetical land until Captain James Cook's ships, HMS Resolution and Adventure, crossed the Antarctic Circle on January 17, 1773, in December 1773 and again in January 1774. Cook in fact came within about 75 miles (121 km) of the Antarctic coast before retreating in the face of field ice in January 1773. The first confirmed sighting of Antarctica can be narrowed down to the crews of ships captained by three individuals. According to various organizations (the National Science Foundation, NASA, the University of California, San Diego, and other source), ships captained by three men sighted Antarctica in 1820: Fabian Gottlieb von Bellingshausen (a captain in the Russian Imperial Navy), Edward Bransfield (a captain in the Royal Navy), and Nathaniel Palmer (an American sealer out of Stonington, Connecticut). Von Bellingshausen saw Antarctica on January 27, 1820, three days before Bransfield sighted land, and ten months before Palmer did so in November 1820. On that day the two-ship expedition led by Von Bellingshausen and Mikhail Petrovich Lazarev reached a point within 32 kilometers (20 mi) of the Antarctic mainland and saw ice fields there. The first documented landing on mainland Antarctica was by the American sealer John Davis in Western Antarctica on February 7, 1821, although some historians dispute this claim.

    In December 1839, as part of the United States Exploring Expedition of 1838–42 conducted by the United States Navy (sometimes called the "Ex. Ex.", or "the Wilkes Expedition"), an expedition sailed from Sydney, Australia, into the Antarctic Ocean, as it was then known, and reported the discovery "of an Antarctic continent west of the Balleny Islands". That part of Antarctica was later named "Wilkes Land", a name it maintains to this day.

    In 1841, explorer James Clark Ross passed through what is now known as the Ross Sea and discovered Ross Island (both of which were named for him). He sailed along a huge wall of ice that was later named the Ross Ice Shelf (also named for him). Mount Erebus and Mount Terror are named after two ships from his expedition: HMS Erebus and Terror.Mercator Cooper landed in Eastern Antarctica on January 26, 1853.

    During an expedition led by Ernest Shackleton in 1907, parties led by T. W. Edgeworth David became the first to climb Mount Erebus and to reach the South Magnetic Pole. Douglas Mawson, who assumed the leadership of the Magnetic Pole party on their perilous return, went on to lead several expeditions until retiring in 1931. In addition, Shackleton himself and three other members of his expedition made several firsts in December 1908 – February 1909: they were the first humans to traverse the Ross Ice Shelf, the first to traverse the Transantarctic Mountain Range (via the Beardmore Glacier), and the first to set foot on the South Polar Plateau. On December 14, 1911, an expedition led by Norwegian polar explorer Roald Amundsen from the ship Fram became the first to reach the geographic South Pole, using a route from the Bay of Whales and up the Axel Heiberg Glacier. One month later, the ill-fated Scott Expedition reached the pole.

    Richard Evelyn Byrd led several voyages to the Antarctic by plane in the 1930s and 1940s. He is credited with implementing mechanized land transport on the continent and conducting extensive geological and biological research. However, it was not until October 31, 1956 that anyone set foot on the South Pole again; on that day a U.S. Navy group led by Rear Admiral George J. Dufek successfully landed an aircraft there.

    Centered asymmetrically around the South Pole and largely south of the Antarctic Circle, Antarctica is the southernmost continent and is surrounded by the Southern Ocean; alternatively, it may be considered to be surrounded by the southern Pacific, Atlantic, and Indian Oceans, or by the southern waters of the World Ocean. It covers more than 14 million km² (5.4 million sq mi), making it the fifth-largest continent, about 1.3 times larger than Europe. The coastline measures 17,968 kilometers (11,160 mi) and is mostly characterized by ice formations.

    A satellite composite image of Antarctica.

    Maritime Antarctica

    Antarctica is divided in two by the Transantarctic Mountains close to the neck between the Ross Sea and the Weddell Sea. The portion west of the Weddell Sea and east of the Ross Sea is called Western Antarctica and the remainder Eastern Antarctica, because they roughly correspond to the Western and Eastern Hemispheres relative to the Greenwich meridian.

    About 98% of Antarctica is covered by the Antarctic ice sheet, a sheet of ice averaging at least 1.6 kilometers (1.0 mi) thick. The continent has about 90% of the world's ice (and thereby about 70% of the world's fresh water). If all of this ice were melted, sea levels would rise about 60 meters (200 ft).[17] In most of the interior of the continent, precipitation is very low, down to 20 millimeters (0.8 in) per year; in a few "blue ice" areas precipitation is lower than mass loss by sublimation and so the local mass balance is negative. In the dry valleys the same effect occurs over a rock base, leading to a desiccated landscape.

    Western Antarctica is covered by the West Antarctic Ice Sheet. The sheet has been of recent concern because of the real, if small, possibility of its collapse. If the sheet were to break down, ocean levels would rise by several meters in a relatively geologically short period of time, perhaps a matter of centuries. Several Antarctic ice streams, which account for about 10% of the ice sheet, flow to one of the many Antarctic ice shelves.

    Vinson Massif, the highest peak in Antarctica at 4,892 meters (16,050 ft), is located in the Ellsworth Mountains. Although Antarctica is home to many volcanoes, only Mount Erebus is known to be active. Located on Ross Island, Erebus is the southernmost active volcano. There is another famous volcano called Deception Island, which is famous for its giant eruption in 1970. Minor eruptions are frequent and lava flow has been observed in recent years. Other dormant volcanoes may potentially be active.[18] In 2004, an underwater volcano was found in the Antarctic Peninsula by American and Canadian researchers. Recent evidence shows this unnamed volcano may be active.

    Antarctica is home to more than 70 lakes that lie thousands of meters under the surface of the continental ice sheet. Lake Vostok, discovered beneath Russia's Vostok Station in 1996, is the largest of these subglacial lakes. It is believed that the lake has been sealed off for 500,000 to one million years. There is some evidence, in the form of ice cores drilled to about 400 meters (1,300 ft) above the water line, that Vostok's waters may contain microbial life. The sealed, frozen surface of the lake shares similarities with Jupiter's moon Europa. If life is discovered in Lake Vostok, this would strengthen the argument for the possibility of life on Europa. On February 7, 2008, a NASA team embarked on a mission to Lake Untersee, searching for extremophiles in its highly-alkaline waters. If found, these resilient creatures could further bolster the argument for extraterrestrial life in extremely cold, methane-rich environments.

    Mount Erebus, an active volcano on Ross Island.


    The blue ice covering Lake Fryxell, in the Transantarctic Mountains, comes from glacial meltwater from the Canada Glacier and other smaller glaciers.
    Antarctica is the coldest place on Earth. At the 3-kilometer (2 mi)-high Vostok Station in Antarctica, scientists recorded the world's lowest temperature: −89 °C (−129 °F). For comparison, this is 11 degrees colder than sublimating dry ice. Antarctica is a frozen desert with little precipitation; the South Pole itself receives less than 10 centimeters (4 in) per year, on average. Temperatures reach a minimum of between −80 °C and −90 °C (−112 °F and −130 °F) in the interior in winter and reach a maximum of between 5 °C and 15 °C (41 °F and 59 °F) near the coast in summer. Sunburn is often a health issue as the snow surface reflects almost all of the ultraviolet light falling on it. Eastern Antarctica is colder than its western counterpart because of its higher elevation. Weather fronts rarely penetrate far into the continent, leaving the center cold and dry. Despite the lack of precipitation over the central portion of the continent, ice there lasts for extended time periods. Heavy snowfalls are not uncommon on the coastal portion of the continent, where snowfalls of up to 1.22 meters (48 in) in 48 hours have been recorded.

    At the edge of the continent, strong katabatic winds off the polar plateau often blow at storm force. In the interior, however, wind speeds are typically moderate. During summer, more solar radiation reaches the surface during clear days at the South Pole than at the equator because of the 24 hours of sunlight each day at the Pole.

    Antarctica is colder than the Arctic for two reasons. First, much of the continent is more than 3 kilometers (2 mi) above sea level, and temperature decreases with elevation. Second, the Arctic Ocean covers the north polar zone: the ocean's relative warmth is transferred through the icepack and prevents temperatures in the Arctic regions from reaching the extremes typical of the land surface of Antarctica.

    Given the latitude, long periods of constant darkness or constant sunlight create climates unfamiliar to human beings in much of the rest of the world. The aurora australis, commonly known as the southern lights, is a glow observed in the night sky near the South Pole. Another unique spectacle is diamond dust, a ground-level cloud composed of tiny ice crystals. It generally forms under otherwise clear or nearly clear skies, so people sometimes also refer to it as clear-sky precipitation. A sun dog, a frequent atmospheric optical phenomenon, is a bright "spot" beside the true sun.

    Antarctica has no permanent residents, but a number of governments maintain permanent research stations throughout the continent. The number of people conducting and supporting scientific research and other work on the continent and its nearby islands varies from about 4,000 in summer to about 1,000 in winter. Many of the stations are staffed year-round.

    The first semi-permanent inhabitants of regions near Antarctica (areas situated south of the Antarctic Convergence) were British and American sealers who used to spend a year or more on South Georgia, from 1786 onward. During the whaling era, which lasted until 1966, the population of that island varied from over 1,000 in the summer (over 2,000 in some years) to some 200 in the winter. Most of the whalers were Norwegian, with an increasing proportion of Britons. The settlements included Grytviken, Leith Harbour, King Edward Point, Stromness, Husvik, Prince Olav Harbour, Ocean Harbour and Godthul. Managers and other senior officers of the whaling stations often lived together with their families. Among them was the founder of Grytviken, Captain Carl Anton Larsen, a prominent Norwegian whaler and explorer who, along with his family, adopted British citizenship in 1910.

    The first child born in the southern polar region was Norwegian girl Solveig Gunbjörg Jacobsen, born in Grytviken on 8 October 1913, and her birth was registered by the resident British Magistrate of South Georgia. She was a daughter of Fridthjof Jacobsen, the assistant manager of the whaling station, and of Klara Olette Jacobsen. Jacobsen arrived on the island in 1904 to become the manager of Grytviken, serving from 1914 to 1921; two of his children were born on the island.

    Emilio Marcos Palma was the first person born on the Antarctic mainland, at Base Esperanza in 1978; his parents were sent there along with seven other families by the Argentinean government to determine if family life was suitable on the continent. In 1984, Juan Pablo Camacho was born at the Frei Montalva Station, becoming the first Chilean born in Antarctica. Several bases are now home to families with children attending schools at the station.

    The climate of Antarctica does not allow extensive vegetation. A combination of freezing temperatures, poor soil quality, lack of moisture, and lack of sunlight inhibit the flourishing of plants. As a result, plant life is limited to mostly mosses and liverworts. The autotrophic community is made up of mostly protists. The flora of the continent largely consists of lichens, bryophytes, algae, and fungi. Growth generally occurs in the summer, and only for a few weeks at most.

    There are more than 200 species of lichens and about 50 species of bryophytes, such as mosses. Seven hundred species of algae exist, most of which are phytoplankton. Multicolored snow algae and diatoms are especially abundant in the coastal regions during the summer. There are two species of flowering plants found in the Antarctic Peninsula: Deschampsia antarctica (Antarctic hair grass) and Colobanthus quitensis (Antarctic pearlwort).

    Land fauna is nearly completely invertebrate. Invertebrate life includes microscopic mites, lice, nematodes, tardigrades, rotifers, krill and springtails. The flightless midge Belgica antarctica, just 12 millimeters (0.5 in) in size, is the largest purely terrestrial animal in Antarctica. The Snow Petrel is one of only three birds that breed exclusively in Antarctica. They have been seen at the South Pole.

    Due to the extreme cold, the body fluids of tiny mites and midges in Antarctica contain glycerol, an antifreeze liquid that protects them from solidifying when temperatures plummet to as low as −34 °C (−30 °F).

    A variety of marine animals exist and rely, directly or indirectly, on the phytoplankton. Antarctic sea life includes penguins, blue whales, orcas and fur seals. The Emperor penguin is the only penguin that breeds during the winter in Antarctica, while the Adélie Penguin breeds farther south than any other penguin. The Rockhopper penguin has distinctive feathers around the eyes, giving the appearance of elaborate eyelashes. King penguins, Chinstrap penguins, and Gentoo Penguins also breed in the Antarctic.

    The Antarctic fur seal was very heavily hunted in the 18th and 19th centuries for its pelt by sealers from the United States and the United Kingdom. The Weddell Seal, a "true seal", is named after Sir James Weddell, commander of British sealing expeditions in the Weddell Sea. Antarctic krill, which congregates in large schools, is the keystone species of the ecosystem of the Southern Ocean, and is an important food organism for whales, seals, leopard seals, fur seals, squid, icefish, penguins, albatrosses and many other birds.[31]

    The passing of the Antarctic Conservation Act in the U.S. brought several restrictions to U.S. activity on the continent. The introduction of alien plants or animals can bring a criminal penalty, as can the extraction of any indigenous species. The overfishing of krill, which plays a large role in the Antarctic ecosystem, led officials to enact regulations on fishing. The Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR), a treaty that came into force in 1980, requires that regulations managing all Southern Ocean fisheries consider potential effects on the entire Antarctic ecosystem.[3] Despite these new acts, unregulated and illegal fishing, particularly of Patagonian toothfish (marketed as Chilean Sea Bass in the U.S.), remains a serious problem. The illegal fishing of toothfish has been increasing, with estimates of 32,000 tonnes (35,300 short tons) in 2000.

    Emperor Penguins in Ross Sea, Antarctica.


  9. #9
    Gforum Veterano
    Data de Ingresso
    Apr 2007

    Padrão Oceania

    Oceania (sometimes Oceanica) is a geographical, often geopolitical, region consisting of numerous lands—mostly islands in the Pacific Ocean and vicinity. The term is often used in many languages to define one of the continents and is one of eight terrestrial ecozones.

    Ethnologically, the islands that are included in Oceania are divided into the subregions of Melanesia, Micronesia, and Polynesia.

    The exact scope of Oceania is variably defined: it generally includes New Zealand, is often taken to include parts of Australasia such as Australia and New Guinea, and sometimes all or part of the Malay Archipelago.

    Oceania Location

    Originally coined by the French explorer Dumont d'Urville in 1831, Oceania has been traditionally divided into Micronesia, Melanesia and Polynesia. As with any region, however, interpretations vary; increasingly, geographers and scientists divide Oceania into Near Oceania and Remote Oceania.

    Most of Oceania consists of island nations composed of thousands of coral atolls and volcanic islands, with small human populations.

    Australia is the only continental country but Indonesia has land borders with Papua New Guinea, East Timor, and Malaysia. If the Australia-New Guinea continent is included then the highest point is Puncak Jaya in Papua at 4,884 m (16,024 ft) and the lowest point is Lake Eyre, Australia at 16 m (52 ft) below sea level.

    The regions and constituents of Oceania may vary according to source. In the table below, the subregions and countries of Oceania are broadly categorised according to the scheme for geographic subregions used by the United Nations, and data included are per sources in cross-referenced articles. Where they differ, provisos are clearly indicated. Apropos, according to different definitions, the following territories and regions may be subject to various other categorisations.

    Regions of Oceania

    Interpretative details and controversies

    * New Zealand is the western corner of the Polynesian triangle. Its indigenous Māori constitute one of the major cultures of Polynesia. It is also, however, considered part of Australasia.
    * Hawaii is the northern corner of the Polynesian triangle and is generally included in Oceania, though politically it is part of the United States. The Hawaiian language is a Polynesian member of the Oceanic language family, and Hawaiian culture is one of the major cultures of Polynesia.
    * The U.S. territories in the North Pacific are generally considered part of Oceania.
    * Rapa Nui, or Easter Island, is the eastern corner of the Polynesian triangle. A Polynesian island in the eastern Pacific Ocean and part of the territory of Chile, it is generally included in Oceania, in which case the most easterly place in Polynesia and Oceania is its dependency Sala y Gómez 415 km to the East.
    * The line in Indonesia dividing Oceania from Asia varies in location and is sometimes considered to be the Wallace Line. See the transcontinental country article.
    * East Timor is often reckoned as a part of Oceania due to its location to the east of the Wallace Line and its cultural ties to Pacific peoples. See transcontinental country; [1] Biogeographically, East Timor lies within Wallacea, an ecological transition zone between Asia and Australasia. This transition is less known and less favoured these days as a continental boundary.
    * Australia is sometimes not included in Oceania. Terms such as Pacific Islands or South Sea Islands might be used to describe Oceania without Australia (and New Zealand). The term "Australasia" invariably includes Australia, and usually includes New Zealand, Papua New Guinea, and some other parts of Oceania, but this term is sometimes controversial outside of Australia, as it may be seen as indicating a link with Asia — a separate continent — or as too greatly emphasising Australia.[citation needed] "Austral" means "of, relating to, or coming from the south", and is the common root of both Australia and Australasia.
    * Although Christmas Island and the Cocos (Keeling) Islands belong to the Commonwealth of Australia, they are west of Sumatra and are commonly associated with Asia, and not with Oceania.[citation needed]
    * The Philippines, an archipelago in the Western Pacific Ocean, is sometimes included in Oceania, due to its Austronesian people, its role as the centre of the former Spanish East Indies, and as a former naval power in the Pacific when it was a territory of the United States from (1898–1946). Except for Palawan all of its larger islands lie to the East of the Wallace line.
    * In its widest sense, the term may embrace the entire insular region between Asia and the Americas, thereby including other Pacific island groups such as the Ryukyu, Kuril and Aleutian islands, and the Japanese Archipelago.

    Political Map of Oceania

    Oceania is one of eight terrestrial ecozones, which constitute the major ecological regions of the planet. The Oceania ecozone includes all of Micronesia, Fiji, and all of Polynesia except New Zealand. New Zealand, along with New Guinea and nearby islands, Australia, the Solomon Islands, Vanuatu, and New Caledonia, constitute the separate Australasia ecozone.


  10. #10
    Gforum Veterano
    Data de Ingresso
    Apr 2007

    Padrão Volcano

    A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot, molten rock, ash, and gases to escape from below the surface. Volcanic activity involving the extrusion of rock tends to form mountains or features like mountains over a period of time.

    Volcanoes are generally found where tectonic plates are pulled apart or come together. A mid-oceanic ridge, for example the Mid-Atlantic Ridge, has examples of volcanoes caused by "divergent tectonic plates" pulling apart; the Pacific Ring of Fire has examples of volcanoes caused by "convergent tectonic plates" coming together. By contrast, volcanoes are usually not created where two tectonic plates slide past one another. Volcanoes can also form where there is stretching and thinning of the Earth's crust (called "non-hotspot intraplate volcanism"), such as in the African Rift Valley, the Wells Gray-Clearwater Volcanic Field and the Rio Grande Rift in North America and the European Rhine Graben with its Eifel volcanoes.

    Volcanoes can be caused by "mantle plumes". These so-called "hotspots" , for example at Hawaii, can occur far from plate boundaries. Hotspot volcanoes are also found elsewhere in the solar system, especially on rocky planets and moons.


    Cross-section through a stratovolcano:

    1. Large magma chamber
    2. Bedrock
    3. Conduit (pipe)
    4. Base
    5. Sill
    6. Branch pipe
    7. Layers of ash emitted by the volcano
    8. Flank 9. Layers of lava emitted by the volcano
    10. Throat
    11. Parasitic cone
    12. Lava flow
    13. Vent
    14. Crater
    15. Ash cloud

    Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station

    Plate tectonics and hotspots

    Divergent plate boundaries

    At the mid-oceanic ridges, two tectonic plates diverge from one another. New oceanic crust is being formed by hot molten rock slowly cooling and solidifying. The crust is very thin at mid-oceanic ridges due to the pull of the tectonic plates. The release of pressure due to the thinning of the crust leads to adiabatic expansion, and the partial melting of the mantle causing volcanism and creating new oceanic crust. Most divergent plate boundaries are at the bottom of the oceans, therefore most volcanic activity is submarine, forming new seafloor. Black smokers or deep sea vents are an example of this kind of volcanic activity. Where the mid-oceanic ridge is above sea-level, volcanic islands are formed, for example, Iceland.

    Map showing the divergent plate boundaries (OSR – Oceanic Spreading Ridges) and recent sub aerial volcanoes.

    Convergent plate boundaries

    Subduction zones are places where two plates, usually an oceanic plate and a continental plate, collide. In this case, the oceanic plate subducts, or submerges under the continental plate forming a deep ocean trench just offshore. Water released from the subducting plate lowers the melting temperature of the overlying mantle wedge, creating magma. This magma tends to be very viscous due to its high silica content, so often does not reach the surface and cools at depth. When it does reach the surface, a volcano is formed. Typical examples for this kind of volcano are Mount Etna and the volcanoes in the Pacific Ring of Fire.


    Hotspots are not usually located on the ridges of tectonic plates, but above mantle plumes, where the convection of the Earth's mantle creates a column of hot material that rises until it reaches the crust, which tends to be thinner than in other areas of the Earth. The temperature of the plume causes the crust to melt and form pipes, which can vent magma. Because the tectonic plates move whereas the mantle plume remains in the same place, each volcano becomes dormant after a while and a new volcano is then formed as the plate shifts over the hotspot. The Hawaiian Islands are thought to be formed in such a manner, as well as the Snake River Plain, with the Yellowstone Caldera being the part of the North American plate currently above the hotspot.


  11. #11
    Gforum Veterano
    Data de Ingresso
    Apr 2007

    Padrão Volcanic Features

    Volcanic features

    The most common perception of a volcano is of a conical mountain, spewing lava and poisonous gases from a crater at its summit. This describes just one of many types of volcano, and the features of volcanoes are much more complicated. The structure and behavior of volcanoes depends on a number of factors. Some volcanoes have rugged peaks formed by lava domes rather than a summit crater, whereas others present landscape features such as massive plateaus. Vents that issue volcanic material (lava, which is what magma is called once it has escaped to the surface, and ash) and gases (mainly steam and magmatic gases) can be located anywhere on the landform. Many of these vents give rise to smaller cones such as Puʻu ʻŌʻō on a flank of Hawaii's Kīlauea.

    Other types of volcano include cryovolcanoes (or ice volcanoes), particularly on some moons of Jupiter, Saturn and Neptune; and mud volcanoes, which are formations often not associated with known magmatic activity. Active mud volcanoes tend to involve temperatures much lower than those of igneous volcanoes, except when a mud volcano is actually a vent of an igneous volcano.

    Shield volcanoes

    Skjaldbreiður, a shield volcano whose name means "broad shield"

    Shield volcanoes, so named for their broad, shield-like profiles, are formed by the eruption of low-viscosity lavas that can flow a great distance from a vent, but not generally explode catastrophically. The Hawaiian volcanic chain is a series of shield cones, and they are common in Iceland, as well.

    Lava domes

    Lava domes are built by slow eruptions of highly viscous lavas. They are sometimes formed within the crater of a previous volcanic eruption (as in Mount Saint Helens), but can also form independently, as in the case of Lassen Peak. Like stratovolcanoes, they can produce violent, explosive eruptions, but their lavas generally do not flow far from the originating vent.

    Cinder cones

    Volcanic cones or cinder cones result from eruptions that erupt mostly small pieces of scoria and pyroclastics (both resemble cinders, hence the name of this volcano type) that build up around the vent. These can be relatively short-lived eruptions that produce a cone-shaped hill perhaps 30 to 400 meters high. Most cinder cones erupt only once. Cinder cones may form as flank vents on larger volcanoes, or occur on their own. Parícutin in Mexico and Sunset Crater in Arizona are examples of cinder cones.

    (composite volcano)

    Mayon Volcano, a stratovolcano

    Stratovolcanoes are tall conical mountains composed of lava flows and other ejecta in alternate layers, the strata that give rise to the name. Stratovolcanoes are also known as composite volcanoes. Strato/composite volcanoes are made of cinders, ash and lava. The volcanoes are made by another volcano. Cinders and ash pile on top of each other, then lava flows on top and dries and then the process begins again. Classic examples include Mt. Fuji in Japan, Mount Mayon in the Philippines, and Mount Vesuvius and Stromboli in Italy. Within a relatively short geologic time scale stratovolcanoes are more dangerous (see stratovolcano for a list of dangers).


    Supervolcano is the popular term for a large volcano that usually has a large caldera and can potentially produce devastation on an enormous, sometimes continental, scale. Such eruptions would be able to cause severe cooling of global temperatures for many years afterwards because of the huge volumes of sulfur and ash erupted. They are the most dangerous type of volcano. Examples include Yellowstone Caldera in Yellowstone National Park of western USA, Lake Taupo in New Zealand and Lake Toba in Sumatra, Indonesia. Supervolcanoes are hard to identify centuries later, given the enormous areas they cover. Large igneous provinces are also considered supervolcanoes because of the vast amount of basalt lava erupted, but they are non-explosive because only non-explosive eruptions such as Kilauea produce basalt lava.

    Submarine volcanoes

    Pillow lava (NOAA)

    Submarine volcanoes are common features on the ocean floor. Some are active and, in shallow water, disclose their presence by blasting steam and rocky debris high above the surface of the sea. Many others lie at such great depths that the tremendous weight of the water above them prevents the explosive release of steam and gases, although they can be detected by hydrophones and discoloration of water because of volcanic gases. Pumice rafts may also appear. Even large submarine eruptions may not disturb the ocean surface. Because of the rapid cooling effect of water as compared to air, and increased buoyancy, submarine volcanoes often form rather steep pillars over their volcanic vents as compared to above-surface volcanoes. They may become so large that they break the ocean surface as new islands. Pillow lava is a common eruptive product of submarine volcanoes.

    Subglacial volcanoes

    Subglacial volcanoes develop underneath icecaps. They are made up of flat lava flows atop extensive pillow lavas and palagonite. When the icecap melts, the lavas on the top collapse leaving a flat-topped mountain. Then, the pillow lavas also collapse, giving an angle of 37.5 degrees. These volcanoes are also called table mountains, tuyas or (uncommonly) mobergs. Very good examples of this type of volcano can be seen in Iceland, however, there are also tuyas in British Columbia. The origin of the term comes from Tuya Butte, which is one of the several tuyas in the area of the Tuya River and Tuya Range in northern British Columbia. Tuya Butte was the first such landform analyzed and so its name has entered the geological literature for this kind of volcanic formation. The Tuya Mountains Provincial Park was recently established to protect this unusual landscape, which lies north of Tuya Lake and south of the Jennings River near the boundary with the Yukon Territory.

    Antarctica eruption

    In January, 2008, the British Antarctic Survey (Bas) scientists led by Hugh Corr and David Vaughan, reported (in the journal Nature Geoscience) that 2,200 years ago, a volcano erupted under Antarctica ice sheet (based on airborne survey with radar images). The biggest eruption in the last 10,000 years, the volcanic ash was found deposited on the ice surface under the Hudson Mountains, close to Pine Island Glacier.


  12. #12
    Gforum Veterano
    Data de Ingresso
    Apr 2007

    Padrão Erupted material

    Lava composition

    Pāhoehoe Lava flow at Hawaii (island). The picture shows few overflows of a main lava channel.

    Another way of classifying volcanoes is by the composition of material erupted (lava), since this affects the shape of the volcano. Lava can be broadly classified into 4 different compositions (Cas & Wright, 1987):

    * If the erupted magma contains a high percentage (>63%) of silica, the lava is called felsic.
    o Felsic lavas (or rhyolites) tend to be highly viscous (not very fluid) and are erupted as domes or short, stubby flows. Viscous lavas tend to form stratovolcanoes or lava domes. Lassen Peak in California is an example of a volcano formed from felsic lava and is actually a large lava dome.
    o Because siliceous magmas are so viscous, they tend to trap volatiles (gases) that are present, which cause the magma to erupt catastrophically, eventually forming stratovolcanoes. Pyroclastic flows (ignimbrites) are highly hazardous products of such volcanoes, since they are composed of molten volcanic ash too heavy to go up into the atmosphere, so they hug the volcano's slopes and travel far from their vents during large eruptions. Temperatures as high as 1,200 °C are known to occur in pyroclastic flows, which will incinerate everything flammable in their path and thick layers of hot pyroclastic flow deposits can be laid down, often up to many meters thick. Alaska's Valley of Ten Thousand Smokes, formed by the eruption of Novarupta near Katmai in 1912, is an example of a thick pyroclastic flow or ignimbrite deposit. Volcanic ash that is light enough to be erupted high into the Earth's atmosphere may travel many kilometres before it falls back to ground as a tuff.
    * If the erupted magma contains 52–63% silica, the lava is of intermediate composition.
    o These "andesitic" volcanoes generally only occur above subduction zones (e.g. Mount Merapi in Indonesia).
    * If the erupted magma contains <52% and >45% silica, the lava is called mafic (because it contains higher percentages of magnesium (Mg) and iron (Fe)) or basaltic. These lavas are usually much less viscous than rhyolitic lavas, depending on their eruption temperature; they also tend to be hotter than felsic lavas. Mafic lavas occur in a wide range of settings:
    o At mid-ocean ridges, where two oceanic plates are pulling apart, basaltic lava erupts as pillows to fill the gap;
    o Shield volcanoes (e.g. the Hawaiian Islands, including Mauna Loa and Kilauea), on both oceanic and continental crust;
    o As continental flood basalts.
    * Some erupted magmas contain <=45% silica and produce ultramafic lava. Ultramafic flows, also known as komatiites, are very rare; indeed, very few have been erupted at the Earth's surface since the Proterozoic, when the planet's heat flow was higher. They are (or were) the hottest lavas, and probably more fluid than common mafic lavas.

    Lava texture

    Two types of lava are named according to the surface texture: ʻAʻa , both words having Hawaiian origins. ʻAʻa is characterized by a rough, clinkery surface and is what most viscous and hot lava flows look like. However, even basaltic or mafic flows can be erupted as ʻaʻa flows, particularly if the eruption rate is high and the slope is steep. Pāhoehoe is characterized by its smooth and often ropey or wrinkly surface and is generally formed from more fluid lava flows. Usually, only mafic flows will erupt as pāhoehoe, since they often erupt at higher temperatures or have the proper chemical make-up to allow them to flow at a higher fluidity.

    Notable volcanoes

    The 16 current Decade Volcanoes are:

    * Avachinsky-Koryaksky, Kamchatka, Russia
    * Colima, Jalisco and Colima, Mexico
    * Mount Etna, Sicily, Italy
    * Galeras, Nariño, Colombia
    * Mauna Loa, Hawaii, USA
    * Mount Merapi, Central Java, Indonesia
    * Mount Nyiragongo, Democratic Republic of the Congo
    * Mount Rainier, Washington, USA

    * Sakurajima, Kagoshima Prefecture, Japan
    * Santamaria/Santiaguito, Guatemala
    * Santorini, Cyclades, Greece
    * Taal Volcano, Luzon, Philippines
    * Teide, Canary Islands, Spain
    * Ulawun, New Britain, Papua New Guinea
    * Mount Unzen, Nagasaki Prefecture, Japan
    * Vesuvius, Naples, Italy

    There are many different kinds of volcanic activity and eruptions: phreatic eruptions (steam-generated eruptions), explosive eruption of high-silica lava (e.g., rhyolite), effusive eruption of low-silica lava (e.g., basalt), pyroclastic flows, lahars (debris flow) and carbon dioxide emission. All of these activities can pose a hazard to humans. Earthquakes, hot springs, fumaroles, mud pots and geysers often accompany volcanic activity.

    Volcanic "injection"

    The concentrations of different volcanic gases can vary considerably from one volcano to the next. Water vapor is typically the most abundant volcanic gas, followed by carbon dioxide and sulfur dioxide. Other principal volcanic gases include hydrogen sulfide, hydrogen chloride, and hydrogen fluoride. A large number of minor and trace gases are also found in volcanic emissions, for example hydrogen, carbon monoxide, halocarbons, organic compounds, and volatile metal chlorides.

    Large, explosive volcanic eruptions inject water vapor (H2O), carbon dioxide (CO2), sulfur dioxide (SO2), hydrogen chloride (HCl), hydrogen fluoride (HF) and ash (pulverized rock and pumice) into the stratosphere to heights of 16–32 kilometres (10–20 mi) above the Earth's surface. The most significant impacts from these injections come from the conversion of sulfur dioxide to sulfuric acid (H2SO4), which condenses rapidly in the stratosphere to form fine sulfate aerosols. The aerosols increase the Earth's albedo—its reflection of radiation from the Sun back into space - and thus cool the Earth's lower atmosphere or troposphere; however, they also absorb heat radiated up from the Earth, thereby warming the stratosphere. Several eruptions during the past century have caused a decline in the average temperature at the Earth's surface of up to half a degree (Fahrenheit scale) for periods of one to three years. The sulfate aerosols also promote complex chemical reactions on their surfaces that alter chlorine and nitrogen chemical species in the stratosphere. This effect, together with increased stratospheric chlorine levels from chlorofluorocarbon pollution, generates chlorine monoxide (ClO), which destroys ozone (O3). As the aerosols grow and coagulate, they settle down into the upper troposphere where they serve as nuclei for cirrus clouds and further modify the Earth's radiation balance. Most of the hydrogen chloride (HCl) and hydrogen fluoride (HF) are dissolved in water droplets in the eruption cloud and quickly fall to the ground as acid rain. The injected ash also falls rapidly from the stratosphere; most of it is removed within several days to a few weeks. Finally, explosive volcanic eruptions release the greenhouse gas carbon dioxide and thus provide a deep source of carbon for biogeochemical cycles.


  13. #13
    Gforum Veterano
    Data de Ingresso
    Apr 2007

    Padrão Earthquake

    An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. Earthquakes are recorded with a seismometer, also known as a seismograph. The moment magnitude of an earthquake is conventionally reported, or the related and mostly obsolete Richter magnitude, with magnitude 3 or lower earthquakes being mostly imperceptible and magnitude 7 causing serious damage over large areas. Intensity of shaking is measured on the modified Mercalli scale.

    At the Earth's surface, earthquakes manifest themselves by a shaking and sometimes displacement of the ground. When a large earthquake epicenter is located offshore, the seabed sometimes suffers sufficient displacement to cause a tsunami. The shaking in earthquakes can also trigger landslides and occasionally volcanic activity.

    In its most generic sense, the word earthquake is used to describe any seismic event—whether a natural phenomenon or an event caused by humans—that generates seismic waves. Earthquakes are caused mostly by rupture of geological faults, huge amounts of gas migration, mainly methane deep within the earth, but also by volcanic activity, landslides, mine blasts, and nuclear experiments.

    An earthquake's point of initial rupture is called its focus or hypocenter. The term epicenter means the point at ground level directly above this.

    Global earthquake epicenters, 1963–1998

    Global plate tectonic movement

    Naturally occurring earthquakes

    Fault Types

    Tectonic earthquakes will occur anywhere within the earth where there is sufficient stored elastic strain energy to drive fracture propagation along a fault plane. In the case of transform or convergent type plate boundaries, which form the largest fault surfaces on earth, they will move past each other smoothly and aseismically only if there are no irregularities or asperities along the boundary that increase the frictional resistance. Most boundaries do have such asperities and this leads to a form of stick-slip behaviour. Once the boundary has locked, continued relative motion between the plates leads to increasing stress and therefore, stored strain energy in the volume around the fault surface. This continues until the stress has risen sufficiently to break through the asperity, suddenly allowing sliding over the locked portion of the fault, releasing the stored energy. This energy is released as a combination of radiated elastic strain seismic waves, frictional heating of the fault surface, and cracking of the rock, thus causing an earthquake. This process of gradual build-up of strain and stress punctuated by occasional sudden earthquake failure is referred to as the Elastic-rebound theory. It is estimated that only 10 percent or less of an earthquake's total energy is radiated as seismic energy. Most of the earthquake's energy is used to power the earthquake fracture growth or is converted into heat generated by friction. Therefore, earthquakes lower the Earth's available elastic potential energy and raise its temperature, though these changes are negligible compared to the conductive and convective flow of heat out from the Earth's deep interior.

    Earthquakes away from plate boundaries

    Where plate boundaries occur within continental lithosphere, deformation is spread out a over a much larger area than the plate boundary itself. In the case of the San Andreas fault continental transform, many earthquakes occur away from the plate boundary and are related to strains developed within the broader zone of deformation caused by major irregularities in the fault trace (e.g. the “Big bend” region). The Northridge earthquake was associated with movement on a blind thrust within such a zone. Another example is the strongly oblique convergent plate boundary between the Arabian and Eurasian plates where it runs through the northwestern part of the Zagros mountains. The deformation associated with this plate boundary is partitioned into nearly pure thrust sense movements perpendicular to the boundary over a wide zone to the southwest and nearly pure strike-slip motion along the Main Recent Fault close to the actual plate boundary itself. This is demonstrated by earthquake focal mechanisms. [2]

    All tectonic plates have internal stress fields caused by their interactions with neighbouring plates and sedimentary loading or unloading (e.g. deglaciation). These stresses may be sufficient to cause failure along existing fault planes, giving rise to intra-plate earthquakes.

    Deep focus earthquakes

    The majority of tectonic earthquakes originate at depths not exceeding tens of kilometers. In subduction zones, where older and colder oceanic crust descends beneath another tectonic plate, Deep focus earthquakes may occur at much greater depths (up to seven hundred kilometers). These seismically active areas of subduction are known as Wadati-Benioff zones. These are earthquakes that occur at a depth at which the subducted lithosphere should no longer be brittle, due to the high temperature and pressure. A possible mechanism for the generation of deep focus earthquakes is faulting caused by olivine undergoing a phase transition into a spinel structure.[3]

    Earthquakes and volcanic activity

    Earthquakes also often occur in volcanic regions and are caused there, both by tectonic faults and by the movement of magma in volcanoes. Such earthquakes can serve as an early warning of volcanic eruptions.

    Earthquake storms

    Sometimes a series of earthquakes occur in a sort of earthquake storm, where the earthquakes strike a fault in clusters, each triggered by the shaking or stress redistribution of the previous earthquakes. Similar to aftershocks but on adjacent segments of fault, these storms occur over the course of years, and with some of the later earthquakes as damaging as the early ones. Such a pattern was observed in the sequence of about a dozen earthquakes that struck the North Anatolian Fault in Turkey in the 20th century, the half dozen large earthquakes in New Madrid in 1811-1812, and has been inferred for older anomalous clusters of large earthquakes in the Middle East and in the Mojave Desert.


  14. #14
    Gforum Veterano
    Data de Ingresso
    Apr 2007

    Padrão Size and frequency of occurrence

    Minor earthquakes occur nearly constantly around the world in places like California and Alaska in the U.S., as well as in Chile, Peru, Indonesia, Iran, Pakistan the Azores in Portugal, Turkey, New Zealand, Greece, Italy, and Japan,[4] Larger earthquakes occur less frequently, the relationship being exponential; for example, roughly ten times as many earthquakes larger than magnitude 4 occur in a particular time period than earthquakes larger than magnitude 5. In the (low seismicity) United Kingdom, for example, it has been calculated that the average recurrences are:

    * an earthquake of 3.7 - 4.6 every year
    * an earthquake of 4.7 - 5.5 every 10 years
    * an earthquake of 5.6 or larger every 100 years.

    The number of seismic stations has increased from about 350 in 1931 to many thousands today. As a result, many more earthquakes are reported than in the past because of the vast improvement in instrumentation (not because the number of earthquakes has increased). The USGS estimates that, since 1900, there have been an average of 18 major earthquakes (magnitude 7.0-7.9) and one great earthquake (magnitude 8.0 or greater) per year, and that this average has been relatively stable. In fact, in recent years, the number of major earthquakes per year has actually decreased, although this is likely a statistical fluctuation. More detailed statistics on the size and frequency of earthquakes is available from the USGS.

    Most of the world's earthquakes (90%, and 81% of the largest) take place in the 40,000-km-long, horseshoe-shaped zone called the circum-Pacific seismic belt, also known as the Pacific Ring of Fire, which for the most part bounds the Pacific Plate. Massive earthquakes tend to occur along other plate boundaries, too, such as along the Himalayan Mountains.

    With the rapid growth of mega-cities such as Mexico City, Tokyo or Tehran, in areas of high seismic risk, some seismologists are warning that a single quake may claim the lives of up to 3 million people.

    Effects/impacts of earthquakes

    Shaking and ground rupture

    Shaking and ground rupture are the main effects created by earthquakes, principally resulting in more or less severe damage to buildings or other rigid structures. The severity of the local effects depends on the complex combination of the earthquake magnitude, the distance from epicenter, and the local geological and geomorphological conditions, which may amplify or reduce wave propagation. The ground-shaking is measured by ground acceleration.

    1755 copper engraving depicting Lisbon in ruins and in flames after the 1755 Lisbon earthquake. A tsunami overwhelms the ships in the harbor.

    Earthquake damage in Mexico City (1985).

    Damage in Great Hanshin earthquake (1995) in Kobe, Japan.

    Specific local geological, geomorphological, and geostructural features can induce high levels of shaking on the ground surface even from low-intensity earthquakes. This effect is called site or local amplification. It is principally due to the transfer of the seismic motion from hard deep soils to soft superficial soils and to effects of seismic energy focalization owing to typical geometrical setting of the deposits.

    Ground rupture is a visible breaking and displacement of the earth's surface along the trace of the fault, which may be of the order of few metres in the case of major earthquakes. Ground rupture is a major risk for large engineering structures such as dams, bridges and nuclear power stations and requires careful mapping of existing faults to identify any likely to break the ground surface within the life of the structure.

    Landslides and avalanches

    Earthquakes can cause landslides and avalanches, which may cause damage in hilly and mountainous areas.


    Following an earthquake, fires can be generated by break of the electrical power or gas lines. In the event of water mains rupturing and a loss of pressure, it may also become difficult to stop the spread of a fire once it has started.

    Soil liquefaction

    Soil liquefaction occurs when, because of the shaking, water-saturated granular material temporarily loses its strength and transforms from a solid to a liquid. Soil liquefaction may cause rigid structures, as buildings or bridges, to tilt or sink into the liquefied deposits.


    Undersea earthquakes and earthquake-triggered landslides into the sea, can cause Tsunami. See, for example, the 2004 Indian Ocean earthquake.


    Floods may be a secondary effects of earthquakes, if dams are damaged.

    Earthquakes may cause landslips to dam rivers, which then collapse and cause floods.

    Human impacts

    Earthquakes may result in disease, lack of basic necessities, loss of life, higher insurance premiums, general property damage, road and bridge damage, and collapse of buildings or destabilization of the base of buildings which may lead to collapse in future earthquakes.

    Major earthquakes

    Main article: List of earthquakes

    Pre-20th century

    * Pompeii (62 AD).
    * Aleppo Earthquake (1138).
    * Basel earthquake (1356). Major earthquake that struck Central Europe in 1356.
    * Carniola earthquake (1511). A major earthquake that shook a large portion of South-Central Europe. Its epicenter was around the town of Idrija, in today's Slovenia. It caused great damage to structures all over Carniola, including Ljubljana, and in western Carinthia, particularly in Villach and Klagenfurt which were almost completely destroyed. There was some minor damage in Venice and other cities, too.
    * Shaanxi Earthquake (1556). Deadliest known earthquake in history, estimated to have killed 830,000 in China.
    * Dover Straits (1580).
    * Dubrovnik earthquake (1667). Disastrous earthquake in Dubrovnik, Croatia killed about 3/5 of the population.
    * Port Royal Earthquake (1692). An earthquake on June 7, 1692, largely destroyed Port Royal, a safe harbor for pirates, causing two thirds of the city to sink into the Caribbean Sea.
    * The great Sicilian earthquake (1693). As many as 100,000 may have died.
    * Cascadia Earthquake (1700).
    * Tokyo earthquake (1703). 37,000 died.
    * Kamchatka earthquakes (1737) The third biggest earthquake on record measuring 9.3 on the Richter scale.
    * Lisbon earthquake (1755), one of the most destructive and deadly earthquakes in history, killing between 60,000 and 100,000 people and causing a major tsunami that affected parts of Europe, North Africa and the Caribbean.
    * Calabria earthquake (1783). Series of 6 earthquakes in Calabria, Italy killed 50,000.[12]
    * Quito earthquake. (1797) Quito, Viceroyalty of Peru, now the capital of Ecuador, was devastated by an earthquake. 40,000 died.
    * New Madrid Earthquake (1811), and another tremor (1812) that also struck the small Missouri town, was reportedly the strongest ever in North America and made the Mississippi River temporarily change its direction and permanently altered its course in the region.
    * Fort Tejon Earthquake (1857). Estimated Richter Scale above 8, said the strongest earthquake in Southern California history.
    * Great Neapolitan Earthquake (1857). Estimated Richter Scale of 6.9. 11,000 dead.
    * 1872 Lone Pine earthquake (1872). Might been strongest ever measured in California with an estimated Richter Scale of 8.1 said seismologists.
    * Charleston earthquake (1886). Largest earthquake in the southeastern United States, killed 100.
    * Ljubljana earthquake (14. IV. 1895), a series of powerful quakes that ultimately had a vital impact on the city of Ljubljana, being a catalyst of its urban renewal.
    * Assam earthquake of 1897 (1897). Large earthquake that destroyed all masonry structures, measuring more than 8 on the Richter scale.

    20th century

    * San Francisco Earthquake (1906). Between 7.7 and 8.3 magnitudes; killed approximately 3,000 people and caused around $400 million in damage; most devastating earthquake in California and U.S. history.
    * Messina Earthquake (1908). Killed about 60,000 people.
    * Gansu earthquake (1920). Killed 200,000 in Gansu province, China.[13]
    * Great Kantō earthquake (1923). On the Japanese island of Honshū, killing over 140,000 in Tokyo and environs.
    * 1931 Hawke's Bay earthquake. Occurred in the Hawkes Bay in the North Island of New Zealand leaving 256 dead.
    * 1933 Long Beach earthquake
    * 1935 Balochistan earthquake at Quetta, Pakistan measuring 7.7 on the Richter scale. Anywhere from 30,000 to 60,000 people died
    * 1939 Erzincan earthquake at Erzincan, Turkey measuring 7.9 on the Richter scale.
    * Ashgabat earthquake (1948). Earthquake in Ashgabat, Soviet Union measuring 7.3 on the Richter scale killed over 110,000 (2/3 the population of the city).[14]
    * Assam earthquake of 1950 (1950). Earthquake in Assam, India measures 8.6M.
    * Kamchatka earthquakes (1952 and 1737), measuring >9.0.
    * Great Kern County earthquake (1952). This was second strongest tremor in Southern California history, epicentered 60 miles North of Los Angeles. Major damage in Bakersfield, California and Kern County, California, while it shook the Los Angeles area.
    * 1959 Yellowstone earthquake, formed Quake Lake in southern Montana, USA
    * Great Chilean Earthquake (1960). Strongest earthquake ever recorded,[15] 9.5 on Moment magnitude scale, and generated tsunamis throughout the Pacific ocean. It measured 9.6 on the Richter scale. [16]
    * 1960 Agadir earthquake, Morocco with around 15,000 casualties.
    * 1963 Skopje earthquake, measuring 6.1 on the Richter scale kills 1,800 people, leaves another 120,000 homeless, and destroys 80% of the city.
    * Good Friday Earthquake (1964) In Alaska, it was the fourth biggest earthquake recorded,[17] measuring 9.2M. and generated tsunamis throughout the Pacific ocean.
    * 1966 Tashkent Earthquake. Ruined most of Tashkent, Uzbek SSR, USSR (now Uzbekistan), tens of thousands of deaths.
    * Ancash earthquake (1970). Caused a landslide that buried the town of Yungay, Peru; killed over 40,000 people.
    * Sylmar earthquake (1971). Caused great and unexpected destruction of freeway bridges and flyways in the San Fernando Valley, leading to the first major seismic retrofits of these types of structures, but not at a sufficient pace to avoid the next California freeway collapse in 1989.
    * Managua earthquake (1972), which killed more than 10,000 people and destroyed 90% of the city. The earthquake took place on December 23, 1972 at midnight.
    * Friuli earthquake (1976), Which killed more than 2.000 people in Northeastern Italy and in the Slovenian Littoral on the 6th of May
    * Tangshan earthquake (1976). The most destructive earthquake of modern times. The official death toll was 255,000, but many experts believe that two or three times that number died.
    * Guatemala 1976 earthquake (1976). Causing 23,000 deaths, 77,000 injuries and the destruction of more than 250,000 homes.
    * Vrancea, Romania earthquake (1977). 7.2-7.4 on the Richter scale. Over 1500 people killed, the majority in the Romanian capital Bucharest.
    * Coalinga, California earthquake (1983). 6.5 on the Richter scale on a section of the San Andreas Fault. Six people killed, downtown Coalinga, California devastated and oil field blazes.
    * Great Mexican Earthquake (1985). Killed over 6,500 people, according to official Mexican government reports,[citation needed] but as many as 30,000 people are thought to have been killed (they disappeared and never reappeared after the initial Earthquakes).
    * Great San Salvador Earthquake (October 10, 1986). Killed over 1,500 people.
    * Whittier Narrows earthquake (1987).
    * 1989 Newcastle earthquake, Australia
    * Armenian earthquake (1988). Killed over 25,000.
    * Loma Prieta earthquake (1989). Severely affecting Santa Cruz, San Francisco, San Jose and Oakland in California. This is also called the World Series Earthquake. It struck as Game 3 of the 1989 World Series was just getting underway at Candlestick Park in San Francisco. Revealed necessity of accelerated seismic retrofit of road and bridge structures.
    * Iran Earthquake (1990). 7.7 on the Richter scale. Killed over 35,000 in Gilan Province, southwest of Caspian sea.[18]
    * Luzon Earthquake (1990). On 16 July 1990, an earthquake measuring 7.7 on the Richter scale struck the island of Luzon, Philippines.
    * Landers, California earthquake (1992). Serious damage in the small town of Yucca Valley, California and was felt across 10 states in Western U.S. Another tremor measured 6.4 struck 3 hours later and felt across Southern California.
    * August 1993 Guam Earthquake, measuring 8.2 on the Richter scale and lasting 60 seconds.
    * 1993 Latur earthquake Latur Earthquake,an earthquake of magnitude 6.3 on Richter Scale rocked the districts of Latur and Osmanabad in Maharashtra in India.The degree of fury was such that dwellings in several villages of these 2 districts were totally converted to debris. In adjoining Karnataka state, 9 people were killed and about 16,000 people injured. A huge number of houses were damaged.[19]
    * Northridge, California earthquake (1994). Damage showed seismic resistance deficiencies in modern low-rise apartment construction.
    * Sakhalin earthquake (1995). Measuring 7.6 on the Richter scale, killing over 2,000 people in Sakhalin, Russia.[20]
    * Great Hanshin earthquake (1995). Killed over 6,400 people in and around Kobe, Japan.
    * 1998 Afghanistan earthquake (1998). 6.9 on the Richter scale. Some 125 villages were damaged and 4000 people killed.[21]
    * Athens earthquake (1999). 5.9 on the Richter scale, it hit Athens on September 7. Epicentered 10 miles north of the Greek capital, it claimed 143 lives.
    * Chi-Chi earthquake (1999) Also called the 921 earthquake. Struck Taiwan on September 21, 1999. Over 2,000 people killed, destroyed or damaged over ten thousand buildings. Caused world computer prices to rise sharply.
    * Armenia, Colombia (1999) 6.2 on the Richter scale, Killed over 2,000 in the Colombian Coffee Grown Zone.
    * 1999 İzmit earthquake measuring 7.5 on the Richter scale and killed over 40,000 people and left approximately half a million people homeless in northwestern Turkey.
    * Hector Mine earthquake (1999). 7.1 on the Richter scale, epicentered 30 miles east of Barstow, California, widely felt in California and Nevada.
    * 1999 Düzce earthquake at Düzce, Turkey measuring 7.2 on the Richter scale.
    * Baku earthquake (2000).

    21st century

    * Nisqually Earthquake (2001).
    * El Salvador earthquakes (2001). 7.9 (13 January) and 6.6 (13 February) magnitudes, killed more than 1,100 people.
    * Gujarat Earthquake (26 January 2001).
    * Hindu Kush earthquakes (2002). Over 1,100 killed.
    * Molise earthquake (2002) 26 killed.
    * Bam Earthquake (2003). Over 40,000 people are reported dead.
    * Parkfield, California earthquake (2004). Not large (6.0), but the most anticipated and intensely instrumented earthquake ever recorded and likely to offer insights into predicting future earthquakes elsewhere on similar slip-strike fault structures.
    * Chūetsu earthquake (2004).
    * Sumatra-Andaman Earthquake (26 December 2004). By some estimates, the second largest earthquake in recorded history (estimates of magnitude vary between 9.1[22] and 9.3). Epicentered off the coast of the Indonesian island of Sumatra, this massive earthquake triggered a series of gigantic tsunamis that smashed onto the shores of a number of nations, causing 230,000 fatalities.
    * Sumatran (Nias) Earthquake (2005).
    * Fukuoka earthquake (2005).
    * Northern Chile Earthquake (2005). 7.9 (13 June). Killed only 15 people, but left many poor families homeless.
    * Kashmir earthquake (2005) (also known as the Great Pakistan earthquake). Killed over 79,000 people; and many more injured.
    * Lake Tanganyika earthquake (2005).
    * May 2006 Java earthquake (2006).
    * July 2006 7.7 magnitude Java earthquake which triggered tsunamis (2006).
    * October 2006 6.6 magnitude Kona, Hawaii earthquake (2006).
    * November 2006 8.1 magnitude north of Japan (2006).
    * December 26, 2006, 7.2 magnitude, southwest of Taiwan (2006).
    * Sumatra Earthquakes March 06, 2007, 6.4 and 6.3 magnitude, Sumatra, Indonesia (2007).
    * March 25, 2007, 6.9 magnitude, off the west coast of Honshū, Japan (2007).
    * April 1, 2007, 8.1 magnitude, Solomon Islands (2007).
    * 2007 Guatemala Earthquake 6.7 magnitude (2007).
    * July 16, 2007, 6.6 magnitude, Niigata prefecture, Japan (2007).
    * 2007 Peru earthquake 8.0 magnitude, August 15 (2007)[23]
    * September 2007 Sumatra earthquakes 8.0 magnitude September 12 (2007)[24]
    * November 14, 2007, 7.7 magnitude, Antofagasta, Chile (2007).
    * November 29, 2007, 7.4 magnitude, Caribbean Sea (2007).
    * December 20, 2007 6.8 magnitude, Gisborne, New Zealand (2007).
    * February 20, 2008 Sumatra earthquake 7.5 magnitude[25]
    * February 25, 2008 Sumatra earthquake 7.3 magnitude. The quake was centered about 160 km (100 miles) south-southwest of Padang. The Pacific Tsunami Warning Center issued a local tsunami watch.[26]
    * March 21, 2008 China earthquake 7.2 magnitude. The quake happened in Yutian County, Xinjiang, a remote region in the Kunlun Mountains far from any residential areas.[27]
    * March 29, 2008 Sumatra earthquake 6.3 magnitude. The epicenter was about 175 miles (281 kilometers) south of Banda Aceh -- in a region hard-hit by the 2004 Indian Ocean earthquake. The Pacific Tsunami Warning Center issued warnings on the possibility of the quake triggering tsunamis on coasts near its epicenter.[28]
    * April 8, 2008 earthquake 7.5 magnitude. The quake was in the southern Pacific Ocean, about 85 kilometers southwest of Vanuatu.
    * May 12, 2008 earthquake 8.0 magnitude about 60 kilometers northwest of Chengdu in the Sichuan province in China, killed over 32,476 people, expected to soar and China admits quake death toll could exceed 50000.

    Earthquakes in mythology and religion

    In Norse mythology, earthquakes were explained as the violent struggling of the god Loki. When Loki, god of mischief and strife, murdered Baldr, god of beauty and light, he was punished by being bound in a cave with a poisonous serpent placed above his head dripping venom. Loki's wife Sigyn stood by him with a bowl to catch the poison, but whenever she had to empty the bowl the poison would drip on Loki's face, forcing him to jerk his head away and thrash against his bonds, causing the earth to tremble.
    In Greek mythology, Poseidon was the god of earthquakes.

    Source: wikipedia

  15. #15
    Gforum Veterano
    Data de Ingresso
    Apr 2007

    Padrão Tropycal cyclone

    A tropical cyclone is a storm system characterized by a low pressure center and numerous thunderstorms that produce strong winds and flooding rain. A tropical cyclone feeds on heat released when moist air rises, resulting in condensation of water vapour contained in the moist air. They are fueled by a different heat mechanism than other cyclonic windstorms such as nor'easters, European windstorms, and polar lows, leading to their classification as "warm core" storm systems.

    The term "tropical" refers to both the geographic origin of these systems, which form almost exclusively in tropical regions of the globe, and their formation in Maritime Tropical air masses. The term "cyclone" refers to such storms' cyclonic nature, with counterclockwise rotation in the Northern Hemisphere and clockwise rotation in the Southern Hemisphere. Depending on their location and strength, tropical cyclones are referred to by other names, such as hurricane, typhoon, tropical storm, cyclonic storm, tropical depression and simply cyclone.

    While tropical cyclones can produce extremely powerful winds and torrential rain, they are also able to produce high waves and damaging storm surge. They develop over large bodies of warm water, and lose their strength if they move over land. This is the reason coastal regions can receive significant damage from a tropical cyclone, while inland regions are relatively safe from receiving strong winds. Heavy rains, however, can produce significant flooding inland, and storm surges can produce extensive coastal flooding up to 40 kilometres (25 mi) from the coastline. Although their effects on human populations can be devastating, tropical cyclones can also relieve drought conditions. They also carry heat and energy away from the tropics and transport it toward temperate latitudes, which makes them an important part of the global atmospheric circulation mechanism. As a result, tropical cyclones help to maintain equilibrium in the Earth's troposphere, and to maintain a relatively stable and warm temperature worldwide.

    Many tropical cyclones develop when the atmospheric conditions around a weak disturbance in the atmosphere are favorable. Others form when other types of cyclones acquire tropical characteristics. Tropical systems are then moved by steering winds in the troposphere; if the conditions remain favorable, the tropical disturbance intensifies, and can even develop an eye. On the other end of the spectrum, if the conditions around the system deteriorate or the tropical cyclone makes landfall, the system weakens and eventually dissipates.

    Cyclone Catarina, a rare South Atlantic tropical cyclone viewed from the International Space Station on March 26, 2004

    Physical structure

    Structure of a tropical cyclone

    All tropical cyclones are areas of low atmospheric pressure near the Earth's surface. The pressures recorded at the centers of tropical cyclones are among the lowest that occur on Earth's surface at sea level. Tropical cyclones are characterized and driven by the release of large amounts of latent heat of condensation, which occurs when moist air is carried upwards and its water vapor condenses. This heat is distributed vertically around the center of the storm. Thus, at any given altitude (except close to the surface, where water temperature dictates air temperature) the environment inside the cyclone is warmer than its outer surroundings.


    Rainbands are bands of showers and thunderstorms that spiral cyclonically toward the storm center. High wind gusts and heavy downpours often occur in individual rainbands, with relatively calm weather between bands. Tornadoes often form in the rainbands of landfalling tropical cyclones. Intense annular tropical cyclones are distinctive for their lack of rainbands; instead, they possess a thick circular area of disturbed weather around their low pressure center.[4] While all surface low pressure areas require divergence aloft to continue deepening, the divergence over tropical cyclones is in all directions away from the center. The upper levels of a tropical cyclone feature winds directed away from the center of the storm with an anticyclonic rotation, due to the Coriolis effect. Winds at the surface are strongly cyclonic, weaken with height, and eventually reverse themselves. Tropical cyclones owe this unique characteristic to requiring a relative lack of vertical wind shear to maintain the warm core at the center of the storm.

    Eye and inner core

    A strong tropical cyclone will harbor an area of sinking air at the center of circulation. If this area is strong enough, it can develop into an eye. Weather in the eye is normally calm and free of clouds, although the sea may be extremely violent.[3] The eye is normally circular in shape, and may range in size from 3 kilometres (1.9 mi) to 370 kilometres (230 mi) in diameter.[7][8] Intense, mature tropical cyclones can sometimes exhibit an inward curving of the eyewall's top, making it resemble a football stadium; this phenomenon is thus sometimes referred to as the stadium effect.

    There are other features that either surround the eye, or cover it. The central dense overcast is the concentrated area of strong thunderstorm activity near the center of a tropical cyclone; in weaker tropical cyclones, the CDO may cover the center completely. The eyewall is a circle of strong thunderstorms that surrounds the eye; here is where the greatest wind speeds are found, where clouds reach the highest, and precipitation is the heaviest. The heaviest wind damage occurs where a tropical cyclone's eyewall passes over land. Eyewall replacement cycles occur naturally in intense tropical cyclones. When cyclones reach peak intensity they usually have an eyewall and radius of maximum winds that contract to a very small size, around 10 kilometres (6.2 mi) to 25 kilometres (16 mi). Outer rainbands can organize into an outer ring of thunderstorms that slowly moves inward and robs the inner eyewall of its needed moisture and angular momentum. When the inner eyewall weakens, the tropical cyclone weakens (in other words, the maximum sustained winds weaken and the central pressure rises.) The outer eyewall replaces the inner one completely at the end of the cycle. The storm can be of the same intensity as it was previously or even stronger after the eyewall replacement cycle finishes. The storm may strengthen again as it builds a new outer ring for the next eyewall replacement.

    One measure of the size of a tropical cyclone is determined by measuring the distance from its center of circulation to its outermost closed isobar, also known as its ROCI. If the radius is less than two degrees of latitude or 222 kilometres (138 mi), then the cyclone is "very small" or a "midget". Radii between 3 and 6 latitude degrees or 333 kilometres (207 mi) to 666 kilometres (414 mi) are considered "average sized". "Very large" tropical cyclones have a radius of greater than 8 degrees or 888 kilometres (552 mi). Other methods of determining a tropical cyclone's size include measuring the radius of gale force winds and measuring the radius at which its relative vorticity field decreases to 1×10-5 s-1 from its center

    There are six Regional Specialized Meteorological Centres (RSMCs) worldwide. These organizations are designated by the World Meteorological Organization and are responsible for tracking and issuing bulletins, warnings, and advisories about tropical cyclones in their designated areas of responsibility. Additionally, there are six Tropical Cyclone Warning Centres (TCWCs) that provide information to smaller regions. The RSMCs and TCWCs are not the only organizations that provide information about tropical cyclones to the public. The Joint Typhoon Warning Center (JTWC) issues advisories in all basins except the Northern Atlantic for the purposes of the United States Government. The Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) issues advisories and names for tropical cyclones that approach the Philippines in the Northwestern Pacific to protect the life and property of its citizens. The Canadian Hurricane Centre (CHC) issues advisories on hurricanes and their remnants for Canadian citizens when they affect Canada.

    On March 26, 2004, Cyclone Catarina became the first recorded South Atlantic cyclone and subsequently struck southern Brazil with winds equivalent to Category 2 on the Saffir-Simpson Hurricane Scale. As the cyclone formed outside the authority of another warning center, Brazilian meteorologists initially treated the system as an extratropical cyclone, although subsequently classified it as tropical

    Map of the cumulative tracks of all tropical cyclones during the 1985–2005 time period. The Pacific Ocean west of the International Date Line sees more tropical cyclones than any other basin, while there is almost no activity in the Atlantic Ocean south of the Equator.[/CENTER]


  16. #16
    Gforum Veterano
    Data de Ingresso
    Apr 2007

    Padrão Cyclone Formation



    Worldwide, tropical cyclone activity peaks in late summer, when the difference between temperatures aloft and sea surface temperatures is the greatest. However, each particular basin has its own seasonal patterns. On a worldwide scale, May is the least active month, while September is the most active.

    In the Northern Atlantic Ocean, a distinct hurricane season occurs from June 1 to November 30, sharply peaking from late August through September. The statistical peak of the Atlantic hurricane season is September 10. The Northeast Pacific Ocean has a broader period of activity, but in a similar time frame to the Atlantic. The Northwest Pacific sees tropical cyclones year-round, with a minimum in February and March and a peak in early September. In the North Indian basin, storms are most common from April to December, with peaks in May and November.

    In the Southern Hemisphere, tropical cyclone activity begins in late October and ends in May. Southern Hemisphere activity peaks in mid-February to early March.

    Map of all tropical cyclone tracks from 1945 to 2006. Equal-area


    Waves in the trade winds in the Atlantic Ocean—areas of converging winds that move along the same track as the prevailing wind—create instabilities in the atmosphere that may lead to the formation of hurricanes.
    Waves in the trade winds in the Atlantic Ocean—areas of converging winds that move along the same track as the prevailing wind—create instabilities in the atmosphere that may lead to the formation of hurricanes.

    The formation of tropical cyclones is the topic of extensive ongoing research and is still not fully understood.[36] While six factors appear to be generally necessary, tropical cyclones may occasionally form without meeting all of the following conditions. In most situations, water temperatures of at least 26.5 °C (79.7 °F) are needed down to a depth of at least 50 metres (160 ft); waters of this temperature cause the overlying atmosphere to be unstable enough to sustain convection and thunderstorms.[38] Another factor is rapid cooling with height, which allows the release of the heat of condensation that powers a tropical cyclone. High humidity is needed, especially in the lower-to-mid troposphere; when there is a great deal of moisture in the atmosphere, conditions are more favorable for disturbances to develop. Low amounts of wind shear are needed, as high shear is disruptive to the storm's circulation. Tropical cyclones generally need to form more than 555 kilometres (345 mi) or 5 degrees of latitude away from the equator, allowing the Coriolis effect to deflect winds blowing towards the low pressure center and creating a circulation. Lastly, a formative tropical cyclone needs a pre-existing system of disturbed weather, although without a circulation no cyclonic development will take place.


    Most tropical cyclones form in a worldwide band of thunderstorm activity called by several names: the Intertropical Front (ITF), the Intertropical Convergence Zone (ITCZ), or the monsoon trough. Another important source of atmospheric instability is found in tropical waves, which cause about 85% of intense tropical cyclones in the Atlantic ocean, and become most of the tropical cyclones in the Eastern Pacific basin.

    Tropical cyclones move westward equatorward of the subtropical ridge, intensifying as they move. Most of these systems form between 10 and 30 degrees away of the equator, and 87% form no farther away than 20 degrees of latitude, north or south. Because the Coriolis effect initiates and maintains tropical cyclone rotation, tropical cyclones rarely form or move within about 5 degrees of the equator, where the Coriolis effect is weakest. However, it is possible for tropical cyclones to form within this boundary as Tropical Storm Vamei did in 2001 and Cyclone Agni in 2004.

    Movement and track

    Although tropical cyclones are large systems generating enormous energy, their movements over the Earth's surface are controlled by large-scale winds—the streams in the Earth's atmosphere. The path of motion is referred to as a tropical cyclone's track and has been analogized by Dr. Neil Frank, former director of the National Hurricane Center, to "leaves carried along by a stream".

    Tropical systems, while generally located equatorward of the 20th parallel, are steered primarily westward by the east-to-west winds on the equatorward side of the subtropical ridge—a persistent high pressure area over the world's oceans. In the tropical North Atlantic and Northeast Pacific oceans, trade winds—another name for the westward-moving wind currents—steer tropical waves westward from the African coast and towards the Caribbean Sea, North America, and ultimately into the central Pacific ocean before the waves dampen out.These waves are the precursors to many tropical cyclones within this region. In the Indian Ocean and Western Pacific (both north and south of the equator), tropical cyclogenesis is strongly influenced by the seasonal movement of the Intertropical Convergence Zone and the monsoon trough, rather than by easterly waves.

    Coriolis effect

    The Earth's rotation imparts an acceleration known as the Coriolis effect, Coriolis acceleration, or colloquially, Coriolis force. This acceleration causes cyclonic systems to turn towards the poles in the absence of strong steering currents. The poleward portion of a tropical cyclone contains easterly winds, and the Coriolis effect pulls them slightly more poleward. The westerly winds on the equatorward portion of the cyclone pull slightly towards the equator, but, because the Coriolis effect weakens toward the equator, the net drag on the cyclone is poleward. Thus, tropical cyclones in the Northern Hemisphere usually turn north (before being blown east), and tropical cyclones in the Southern Hemisphere usually turn south (before being blown east) when no other effects counteract the Coriolis effect.

    The Coriolis effect also initiates cyclonic rotation, but it is not the driving force that brings this rotation to high speeds – that force is the heat of condensation.

    Interaction with the mid-latitude westerlies

    When a tropical cyclone crosses the subtropical ridge axis, its general track around the high-pressure area is deflected significantly by winds moving towards the general low-pressure area to its north. When the cyclone track becomes strongly poleward with an easterly component, the cyclone has begun recurvature. A typhoon moving through the Pacific Ocean towards Asia, for example, will recurve offshore of Japan to the north, and then to the northeast, if the typhoon encounters southwesterly winds (blowing northeastward) around a low-pressure system passing over China or Siberia. Many tropical cyclones are eventually forced toward the northeast by extratropical cyclones in this manner, which move from west to east to the north of the subtropical ridge. An example of a tropical cyclone in recurvature was Typhoon Ioke in 2006, which took a similar trajectory.


    Officially, landfall is when a storm's center (the center of its circulation, not its edge) crosses the coastline.[53] Storm conditions may be experienced on the coast and inland hours before landfall; in fact, a tropical cyclone can launch its weakest winds over land, yet not make landfall; if this occurs, then it is said that the storm made a direct hit on the coast. Due to this definition, the landfall area experiences half of a land-bound storm by the time the actual landfall occurs. For emergency preparedness, actions should be timed from when a certain wind speed or intensity of rainfall will reach land, not from when landfall will occur.

    Multiple storm interaction

    When two cyclones approach one another, their centers will begin orbiting cyclonically about a point between the two systems. The two vortices will be attracted to each other, and eventually spiral into the center point and merge. When the two vortices are of unequal size, the larger vortex will tend to dominate the interaction, and the smaller vortex will orbit around it. This phenomenon is called the Fujiwhara effect, after Dr. Sakuhei Fujiwhara.


    A tropical cyclone can cease to have tropical characteristics through several different ways. One such way is if it moves over land, thus depriving it of the warm water it needs to power itself, quickly losing strength. Most strong storms lose their strength very rapidly after landfall and become disorganized areas of low pressure within a day or two, or evolve into extratropical cyclones. While there is a chance a tropical cyclone could regenerate if it managed to get back over open warm water, if it remains over mountains for even a short time, weakening will accelerate.Many storm fatalities occur in mountainous terrain, as the dying storm unleashes torrential rainfall,leading to deadly floods and mudslides, similar to those that happened with Hurricane Mitch in 1998. Additionally, dissipation can occur if a storm remains in the same area of ocean for too long, mixing the upper 60 metres (200 ft) of water, dropping sea surface temperatures more than 5 °C (41 °F). Without warm surface water, the storm cannot survive.

    A tropical cyclone can dissipate when it moves over waters significantly below 26.5 °C (79.7 °F). This will cause the storm to lose its tropical characteristics (i.e. thunderstorms near the center and warm core) and become a remnant low pressure area, which can persist for several days. This is the main dissipation mechanism in the Northeast Pacific ocean. Weakening or dissipation can occur if it experiences vertical wind shear, causing the convection and heat engine to move away from the center; this normally ceases development of a tropical cyclone.[62] Additionally, its interaction with the main belt of the Westerlies, by means of merging with a nearby frontal zone, can cause tropical cyclones to evolve into extratropical cyclones. This transition can take 1–3 days.[63] Even after a tropical cyclone is said to be extratropical or dissipated, it can still have tropical storm force (or occasionally hurricane/typhoon force) winds and drop several inches of rainfall. In the Pacific ocean and Atlantic ocean, such tropical-derived cyclones of higher latitudes can be violent and may occasionally remain at hurricane or typhoon-force wind speeds when they reach the west coast of North America. These phenomena can also affect Europe, where they are known as European windstorms; Hurricane Iris's extratropical remnants are an example of such a windstorm from 1995. Additionally, a cyclone can merge with another area of low pressure, becoming a larger area of low pressure. This can strengthen the resultant system, although it may no longer be a tropical cyclone.

    Artificial dissipation

    In the 1960s and 1970s, the United States government attempted to weaken hurricanes through Project Stormfury by seeding selected storms with silver iodide. It was thought that the seeding would cause supercooled water in the outer rainbands to freeze, causing the inner eyewall to collapse and thus reducing the winds.[65] The winds of Hurricane Debbie—a hurricane seeded in Project Stormfury—dropped as much as 31%, but Debby regained its strength after each of two seeding forays.[66] In an earlier episode in 1947, disaster struck when a hurricane east of Jacksonville, Florida promptly changed its course after being seeded, and smashed into Savannah, Georgia. Because there was so much uncertainty about the behavior of these storms, the federal government would not approve seeding operations unless the hurricane had a less than 10% chance of making landfall within 48 hours, greatly reducing the number of possible test storms. The project was dropped after it was discovered that eyewall replacement cycles occur naturally in strong hurricanes, casting doubt on the result of the earlier attempts. Today, it is known that silver iodide seeding is not likely to have an effect because the amount of supercooled water in the rainbands of a tropical cyclone is too low.

    Other approaches have been suggested over time, including cooling the water under a tropical cyclone by towing icebergs into the tropical oceans. Other ideas range from covering the ocean in a substance that inhibits evaporation, dropping large quantities of ice into the eye at very early stages of development (so that the latent heat is absorbed by the ice, instead of being converted to kinetic energy that would feed the positive feedback loop), or blasting the cyclone apart with nuclear weapons. Project Cirrus even involved throwing dry ice on a cyclone. These approaches all suffer from one flaw above many others: tropical cyclones are simply too large for any of the weakening techniques to be practical.


    Tropical cyclones out at sea cause large waves, heavy rain, and high winds, disrupting international shipping and, at times, causing shipwrecks. Tropical cyclones stir up water, leaving a cool wake behind them, which causes the region to be less favourable for subsequent tropical cyclones. On land, strong winds can damage or destroy vehicles, buildings, bridges, and other outside objects, turning loose debris into deadly flying projectiles. The storm surge, or the increase in sea level due to the cyclone, is typically the worst effect from landfalling tropical cyclones, historically resulting in 90% of tropical cyclone deaths.The broad rotation of a landfalling tropical cyclone, and vertical wind shear at its periphery, spawns tornadoes. Tornadoes can also be spawned as a result of eyewall mesovortices, which persist until landfall.

    Over the past two centuries, tropical cyclones have been responsible for the deaths of about 1.9 million persons worldwide. Large areas of standing water caused by flooding lead to infection, as well as contributing to mosquito-borne illnesses. Crowded evacuees in shelters increase the risk of disease propagation. Tropical cyclones significantly interrupt infrastructure, leading to power outages, bridge destruction, and the hampering of reconstruction efforts.

    Although cyclones take an enormous toll in lives and personal property, they may be important factors in the precipitation regimes of places they impact, as they may bring much-needed precipitation to otherwise dry regions.Tropical cyclones also help maintain the global heat balance by moving warm, moist tropical air to the middle latitudes and polar regions. The storm surge and winds of hurricanes may be destructive to human-made structures, but they also stir up the waters of coastal estuaries, which are typically important fish breeding locales. Tropical cyclone destruction spurs redevelopment, greatly increasing local property values.
    Observation and forecasting

    Sunset view of Hurricane Isidore's rainbands photographed at 7,000 feet (2,100 m)
    Sunset view of Hurricane Isidore's rainbands photographed at 7,000 feet (2,100 m)

    Intense tropical cyclones pose a particular observation challenge, as they are a dangerous oceanic phenomenon, and weather stations, being relatively sparse, are rarely available on the site of the storm itself. Surface observations are generally available only if the storm is passing over an island or a coastal area, or if there is a nearby ship. Usually, real-time measurements are taken in the periphery of the cyclone, where conditions are less catastrophic and its true strength cannot be evaluated. For this reason, there are teams of meteorologists that move into the path of tropical cyclones to help evaluate their strength at the point of landfall.[81]

    Tropical cyclones far from land are tracked by weather satellites capturing visible and infrared images from space, usually at half-hour to quarter-hour intervals. As a storm approaches land, it can be observed by land-based Doppler radar. Radar plays a crucial role around landfall by showing a storm's location and intensity every several minutes.[82]

    In-situ measurements, in real-time, can be taken by sending specially equipped reconnaissance flights into the cyclone. In the Atlantic basin, these flights are regularly flown by United States government hurricane hunters.[83] The aircraft used are WC-130 Hercules and WP-3D Orions, both four-engine turboprop cargo aircraft. These aircraft fly directly into the cyclone and take direct and remote-sensing measurements. The aircraft also launch GPS dropsondes inside the cyclone. These sondes measure temperature, humidity, pressure, and especially winds between flight level and the ocean's surface. A new era in hurricane observation began when a remotely piloted Aerosonde, a small drone aircraft, was flown through Tropical Storm Ophelia as it passed Virginia's Eastern Shore during the 2005 hurricane season. A similar mission was also completed successfully in the western Pacific ocean. This demonstrated a new way to probe the storms at low altitudes that human pilots seldom dare.[84]
    A general decrease in error trends in tropical cyclone path prediction is evident since the 1970s
    A general decrease in error trends in tropical cyclone path prediction is evident since the 1970s

    See also: Tropical cyclone track forecasting, Tropical cyclone prediction model, and Tropical cyclone rainfall forecasting

    Because of the forces that affect tropical cyclone tracks, accurate track predictions depend on determining the position and strength of high- and low-pressure areas, and predicting how those areas will change during the life of a tropical system. The deep layer mean flow, or average wind through the depth of the troposphere, is considered the best tool in determining track direction and speed. If storms are significantly sheared, use of wind speed measurements at a lower altitude, such as at the 700 hPa pressure surface (3,000 metres (9,800 ft) above sea level) will produce better predictions. Tropical forecasters also consider smoothing out short-term wobbles of the storm as it allows them to determine a more accurate long-term trajectory.[85] High-speed computers and sophisticated simulation software allow forecasters to produce computer models that predict tropical cyclone tracks based on the future position and strength of high- and low-pressure systems. Combining forecast models with increased understanding of the forces that act on tropical cyclones, as well as with a wealth of data from Earth-orbiting satellites and other sensors, scientists have increased the accuracy of track forecasts over recent decades.[86] However, scientists are less skillful at predicting the intensity of tropical cyclones.[87] The lack of improvement in intensity forecasting is attributed to the complexity of tropical systems and an incomplete understanding of factors that affect their development.


  17. #17
    Gforum Veterano
    Data de Ingresso
    Apr 2007

    Padrão Cyclone - Classifications, terminology, and naming

    Intensity classifications

    Three tropical cyclones at different stages of development. The weakest (left), demonstrates only the most basic circular shape. A stronger storm (top right) demonstrates spiral banding and increased centralization, while the strongest (lower right) has developed an eye.

    Tropical cyclones are classified into three main groups, based on intensity: tropical depressions, tropical storms, and a third group of more intense storms, whose name depends on the region. For example, if a tropical storm in the Northwestern Pacific reaches hurricane-strength winds on the Beaufort scale, it is referred to as a typhoon; if a tropical storm passes the same benchmark in the Northeast Pacific Basin, or in the Atlantic, it is called a hurricane. Neither "hurricane" nor "typhoon" are used in either the Southern Hemisphere or the Indian Ocean. In these basins, storms of tropical nature are referred as simply "cyclones".

    Additionally, as indicated in the table below, each basin uses a separate system of terminology, making comparisons between different basins difficult. In the Pacific Ocean, hurricanes from the Central North Pacific sometimes cross the International Date Line into the Northwest Pacific, becoming typhoons (such as Hurricane/Typhoon Ioke in 2006); on rare occasions, the reverse will occur. It should also be noted that typhoons with sustained winds greater than 67 metres per second (130 kn) or 150 miles per hour (240 km/h) are called Super Typhoons by the Joint Typhoon Warning Center.

    A tropical depression is an organized system of clouds and thunderstorms with a defined, closed surface circulation and maximum sustained winds of less than 17 metres per second (33 kn) or 39 miles per hour (63 km/h). It has no eye and does not typically have the organization or the spiral shape of more powerful storms. However, it is already a low-pressure system, hence the name "depression".The practice of the Philippines is to name tropical depressions from their own naming convention when the depressions are within the Philippines' area of responsibility.

    A tropical storm is an organized system of strong thunderstorms with a defined surface circulation and maximum sustained winds between 17 metres per second (33 kn) (39 miles per hour (63 km/h)) and 32 metres per second (62 kn) (73 miles per hour (117 km/h)). At this point, the distinctive cyclonic shape starts to develop, although an eye is not usually present. Government weather services, other than the Philippines, first assign names to systems that reach this intensity (thus the term named storm).

    A hurricane or typhoon (sometimes simply referred to as a tropical cyclone, as opposed to a depression or storm) is a system with sustained winds of at least 33 metres per second (64 kn) or 74 miles per hour (119 km/h). A cyclone of this intensity tends to develop an eye, an area of relative calm (and lowest atmospheric pressure) at the center of circulation. The eye is often visible in satellite images as a small, circular, cloud-free spot. Surrounding the eye is the eyewall, an area about 16 kilometres (9.9 mi) to 80 kilometres (50 mi) wide in which the strongest thunderstorms and winds circulate around the storm's center. Maximum sustained winds in the strongest tropical cyclones have been estimated at about 85 metres per second (165 kn) or 195 miles per hour (314 km/h).

    Origin of storm terms

    Taipei 101 endures a typhoon in 2005

    The word typhoon, used today in the Northwest Pacific, may be derived from Urdu, Persian and Arabic ţūfān (طوفان), which in turn originates from Greek tuphōn (Τυφών), a monster in Greek mythology responsible for hot winds. The related Portuguese word tufão, used in Portuguese for typhoons, is also derived from Greek tuphōn.

    The word hurricane, used in the North Atlantic and Northeast Pacific, is derived from the name of a native Caribbean Amerindian storm god, Huracan, via Spanish huracán. (Huracan is also the source of the word Orcan, another word for the European windstorm. These events should not be confused.) Huracan became the Spanish term for hurricanes.


    Storms reaching tropical storm strength were initially given names to eliminate confusion when there are multiple systems in any individual basin at the same time, which assists in warning people of the coming storm. In most cases, a tropical cyclone retains its name throughout its life; however, under special circumstances, tropical cyclones may be renamed while active. These names are taken from lists that vary from region to region and are drafted a few years ahead of time. The lists are decided on, depending on the regions, either by committees of the World Meteorological Organization (called primarily to discuss many other issues), or by national weather offices involved in the forecasting of the storms. Each year, the names of particularly destructive storms (if there are any) are "retired" and new names are chosen to take their place.

    Tropical cyclones that cause extreme destruction are rare, although when they occur, they can cause great amounts of damage or thousands of fatalities.

    The 1970 Bhola cyclone is the deadliest tropical cyclone on record, killing more than 300,000 people and potentially as many as 1 million[99] after striking the densely populated Ganges Delta region of Bangladesh on November 13, 1970. Its powerful storm surge was responsible for the high death toll. The North Indian cyclone basin has historically been the deadliest basin, with several cyclones since 1900 killing more than 100,000 people, all in Bangladesh. Elsewhere, Typhoon Nina killed nearly 100,000 in China due to a 2000-year flood that caused 62 dams including the Banqiao Dam to fail. The Great Hurricane of 1780 is the deadliest Atlantic hurricane on record, killing about 22,000 people in the Lesser Antilles. A tropical cyclone does need not be particularly strong to cause memorable damage, primarily if the deaths are from rainfall or mudslides. Tropical Storm Thelma in November 1991 killed thousands in the Philippines, while in 1982, the unnamed tropical depression that eventually became Hurricane Paul killed around 1,000 people in Central America.
    Hurricane Katrina is estimated as the costliest tropical cyclone worldwide, causing $81.2 billion in property damage (2005 USD) with overall damage estimates exceeding $100 billion (2005 USD). Katrina killed at least 1,836 people after striking Louisiana and Mississippi as a major hurricane in August 2005. The Galveston Hurricane of 1900 is the deadliest natural disaster in the United States, killing an estimated 6,000 to 12,000 people in Galveston, Texas. Hurricane Iniki in 1992 was the most powerful storm to strike Hawaii in recorded history, hitting Kauai as a Category 4 hurricane, killing six people, and causing U.S. $3 billion in damage. Other destructive Eastern Pacific hurricanes include Pauline and Kenna, both causing severe damage after striking Mexico as major hurricanes. In March 2004, Cyclone Gafilo struck northeastern Madagascar as a powerful cyclone, killing 74, affecting more than 200,000, and becoming the worst cyclone to affect the nation for more than 20 years.

    The most intense storm on record was Typhoon Tip in the northwestern Pacific Ocean in 1979, which reached a minimum pressure of 870 mbar (25.69 inHg) and maximum sustained wind speeds of 165 knots (85 m/s) or 190 miles per hour (310 km/h). Tip, however, does not solely hold the record for fastest sustained winds in a cyclone. Typhoon Keith in the Pacific and Hurricanes Camille and Allen in the North Atlantic currently share this record with Tip. Camille was the only storm to actually strike land while at that intensity, making it, with 165 knots (85 m/s) or 190 miles per hour (310 km/h) sustained winds and 183 knots (94 m/s) or 210 miles per hour (340 km/h) gusts, the strongest tropical cyclone on record at landfall. Typhoon Nancy in 1961 had recorded wind speeds of 185 knots (95 m/s) or 215 miles per hour (346 km/h), but recent research indicates that wind speeds from the 1940s to the 1960s were gauged too high, and this is no longer considered the storm with the highest wind speeds on record.[91] Similarly, a surface-level gust caused by Typhoon Paka on Guam was recorded at 205 knots (105 m/s) or 235 miles per hour (378 km/h). Had it been confirmed, it would be the strongest non-tornadic wind ever recorded on the Earth's surface, but the reading had to be discarded since the anemometer was damaged by the storm.

    In addition to being the most intense tropical cyclone on record, Tip was the largest cyclone on record, with tropical storm-force winds 2,170 kilometres (1,350 mi) in diameter. The smallest storm on record, Cyclone Tracy, was roughly 100 kilometres (62 mi) wide before striking Darwin, Australia in 1974.

    Hurricane John is the longest-lasting tropical cyclone on record, lasting 31 days in 1994. Before the advent of satellite imagery in 1961, however, many tropical cyclones were underestimated in their durations. John is the second longest-tracked tropical cyclone in the Northern Hemisphere on record, behind Typhoon Ophelia of 1960, which had a path of 8,500 miles (12,500 km). Reliable data for Southern Hemisphere cyclones is unavailable.

    While the number of storms in the Atlantic has increased since 1995, there is no obvious global trend; the annual number of tropical cyclones worldwide remains about 87 ± 10. However, the ability of climatologists to make long-term data analysis in certain basins is limited by the lack of reliable historical data in some basins, primarily in the Southern Hemisphere. In spite of that, there is some evidence that the intensity of hurricanes is increasing. Kerry Emanuel stated, "Records of hurricane activity worldwide show an upswing of both the maximum wind speed in and the duration of hurricanes. The energy released by the average hurricane (again considering all hurricanes worldwide) seems to have increased by around 70% in the past 30 years or so, corresponding to about a 15% increase in the maximum wind speed and a 60% increase in storm lifetime."

    Atlantic storms are becoming more destructive financially, since five of the ten most expensive storms in United States history have occurred since 1990. This can be attributed to the increased intensity and duration of hurricanes striking North America, and to a greater degree, the number of people living in susceptible coastal areas, following increased development in the region since the last surge in Atlantic hurricane activity in the 1960s.

    Often in part because of the threat of hurricanes, many coastal regions had sparse population between major ports until the advent of automobile tourism; therefore, the most severe portions of hurricanes striking the coast may have gone unmeasured in some instances. The combined effects of ship destruction and remote landfall severely limit the number of intense hurricanes in the official record before the era of hurricane reconnaissance aircraft and satellite meteorology. Although the record shows a distinct increase in the number and strength of intense hurricanes, therefore, experts regard the early data as suspect.
    The number and strength of Atlantic hurricanes may undergo a 50–70 year cycle, also known as the Atlantic Multidecadal Oscillation. Although more common since 1995, few above-normal hurricane seasons occurred during 1970–94. Destructive hurricanes struck frequently from 1926–60, including many major New England hurricanes. Twenty-one Atlantic tropical storms formed in 1933, a record only recently exceeded in 2005, which saw 28 storms. Tropical hurricanes occurred infrequently during the seasons of 1900–25; however, many intense storms formed during 1870–99. During the 1887 season, 19 tropical storms formed, of which a record 4 occurred after 1 November and 11 strengthened into hurricanes. Few hurricanes occurred in the 1840s to 1860s; however, many struck in the early 19th century, including an 1821 storm that made a direct hit on New York City. Some historical weather experts say these storms may have been as high as Category 4 in strength.

    These active hurricane seasons predated satellite coverage of the Atlantic basin. Before the satellite era began in 1960, tropical storms or hurricanes went undetected unless a reconnaissance aircraft encountered one, a ship reported a voyage through the storm, or a storm hit land in a populated area. The official record, therefore, could miss storms in which no ship experienced gale-force winds, recognized it as a tropical storm (as opposed to a high-latitude extra-tropical cyclone, a tropical wave, or a brief squall), returned to port, and reported the experience.


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