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Antarctica
Antarctica is Earth's southernmost continent, underlying the South Pole. It is situated
in the Antarctic region of the southern hemisphere, almost entirely south of the
Antarctic Circle, and is surrounded by the Southern Ocean. At 14.0 million km2 (5.4
million sq mi), it is the fifth-largest continent in area after Asia, Africa, North
America, and South America. About 98% of Antarctica is covered by ice, which
averages at least 1.6 kilometres (1.0 mi) in thickness.
Antarctica, on average, is the coldest, driest, and windiest continent, and has the
highest average elevation of all the continents.[2] Antarctica is considered a desert,
with annual precipitation of only 200 mm (8 inches) along the coast and far less
inland.[3] There are no permanent human residents, but anywhere from 1,000 to 5,000
people reside throughout the year at the research stations scattered across the
continent. Only cold-adapted plants and animals survive there, including penguins,
seals, nematodes, tardigrades, mites, many types of algae and other microorganisms,
and tundra vegetation.
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 Fabian Gottlieb von
Bellingshausen and Mikhail Lazarev. The continent, however, remained largely
neglected for the rest of the 19th century because of its hostile environment, lack of
resources, and isolation. The first formal use of the name "Antarctica" as a continental
name in the 1890s is attributed to the Scottish cartographer John George
Bartholomew. The name Antarctica means opposite to the north".[5]
The Antarctic Treaty was signed in 1959 by twelve countries; to date, forty-six
countries have signed the treaty. The treaty prohibits military activities and mineral
mining, supports scientific research, and protects the continent's ecozone. Ongoingexperiments are conducted by more than 4,000 scientists of many nationalities and
with various research interests.[1]
Europe
Europe is one of the world's seven continents. Comprising the westernmost peninsula
of Eurasia, Europe is generally divided from Asia to its east by the water divide of the
Ural Mountains, the Ural River, the Caspian Sea, the Caucasus region (Specification
of borders) and the Black Sea to the southeast.[2] Europe is bordered by the Arctic
Ocean and other bodies of water to the north, the Atlantic Ocean to the west, the
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Mediterranean Sea to the south, and the Black Sea and connected waterways to the
southeast. Yet the borders for Europea concept dating back to classical antiquity
are somewhat arbitrary, as the term continent can refer to a cultural and political
distinction or a physiographic one.
Europe is the world's second-smallest continent by surface area, covering about
10,180,000 square kilometres (3,930,000 sq mi) or 2% of the Earth's surface and
about 6.8% of its land area. Of Europe's approximately 50 states, Russia is the largest
by both area and population (although the country covers both Europe and Asia),
while the Vatican City is the smallest. Europe is the third-most populous continent
after Asia and Africa, with a population of 731 million or about 11% of the world's
population.
Europe, in particular Ancient Greece, is the birthplace of Western culture.[3] It played
a predominant role in global affairs from the 16th century onwards, especially after
the beginning of colonialism. Between the 16th and 20th centuries, European nations
controlled at various times the Americas, most of Africa, Oceania, and large portions
of Asia. Both World Wars were largely focused upon Europe, greatly contributing to
a decline in Western European dominance in world affairs by the mid-20th century as
the United States and Soviet Union took prominence.[4] During the Cold War, Europe
was divided along the Iron Curtain between NATO in the west and the Warsaw Pact
in the east. European integration led to the formation of the Council of Europe and the
European Union in Western Europe, both of which have been expanding eastward
since the fall of the Soviet Union in 1991.
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the
Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australiain the west, and the Americas in the east.
At 169.2 million square kilometres (63.8 million square miles) in area, this largest
division of the World Ocean and, in turn, the hydrosphere covers about 46% of the
Earth's water surface and about 30% of its total surface.[1] The equator subdivides it
into the North Pacific Ocean and South Pacific Ocean, with two exceptions: the
Galpagos and Gilbert Islands, while straddling the equator, are deemed wholly
within the South Pacific.[2] The Mariana Trench in the western North Pacific is the
deepest point in the Pacific and in the world, reaching a depth of 10,911 metres
(35,797 ft).[3]
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The Pacific Ocean was sighted by Europeans early in the 16th century, first by the
Spanish explorer Vasco Nez de Balboa who crossed the Isthmus of Panama in 1513
and named it Mar del Sur (South Sea). Its current name was given by Portuguese
explorer Ferdinand Magellan during the Spanish expedition of world
circumnavigation in 1521, who encountered calm seas during the journey and called it
Tepre Pacificum in Latin, meaning "pacific" or "peaceful sea".[4]
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering about
20% of the water on the Earth's surface.[1] It is bounded on the north by the Indian
subcontinent; on the west by East Africa; on the east by Indochina, the Sunda Islands,
and Australia; and on the south by the Southern Ocean (or, depending on definition,
by Antarctica). It is the only ocean to be named after a country, i.e., India.[2][3][4]
As one component of the interconnected global ocean, the Indian Ocean is delineated
from the Atlantic Ocean by the 20 east meridian running south from Cape Agulhas,
and from the Pacific by the meridian of 14655' east[5]. The northernmost extent of
the Indian Ocean is approximately 30 north in the Persian Gulf. The Indian Ocean
has asymmetric ocean circulation[citation needed]. This ocean is nearly 10,000
kilometres (6,200 mi) wide at the southern tips of Africa and Australia; its area is
73,556,000 square kilometres (28,400,000 mi2), including the Red Sea and the
Persian Gulf.
The ocean's volume is estimated to be 292,131,000 cubic kilometres (70,086,000
mi3).[6] Small islands dot the continental rims. Island nations within the ocean are
Madagascar, the world's fourth largest island; Reunion Island; Comoros; Seychelles;
Maldives; Mauritius; and Sri Lanka. The archipelago of Indonesia borders the ocean
on the east.
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total
area of about 106,400,000 square kilometres (41,100,000 sq mi), it covers
approximately twenty percent of the Earth's surface and about twenty-six percent of
its water surface area. The first part of its name refers to Atlas of Greek mythology,
making the Atlantic the "Sea of Atlas".
The oldest known mention of "Atlantic" is in The Histories of Herodotus around 450
BC (Hdt. 1.202.4): Atlantis thalassa (Greek: ; English: Sea of
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Atlas); see also: Atlas Mountains. Another name historically used was the ancient
term Ethiopic Ocean, derived from Ethiopia, whose name was sometimes used as a
synonym for all of Africa and thus for the ocean. Before Europeans discovered other
oceans, the term "ocean" itself was synonymous with the waters beyond the Strait of
Gibraltar that we now know as the Atlantic. The Greeks believed this ocean to be a
gigantic river encircling the world.
The Atlantic Ocean occupies an elongated, S-shaped basin extending longitudinally
between the Americas to the west, and Eurasia and Africa to the east. As one
component of the interconnected global ocean, it is connected in the north to the
Arctic Ocean (which is sometimes considered a sea of the Atlantic), to the Pacific
Ocean in the southwest, the Indian Ocean in the southeast, and the Southern Ocean in
the south. (Other definitions describe the Atlantic as extending southward to
Antarctica.) The equator subdivides it into the North Atlantic Ocean and South
Atlantic Ocean.
Arctic Ocean
The Arctic Ocean, located in the Northern Hemisphere and mostly in the Arctic north
polar region, is the smallest, and shallowest of the world's five major oceanic
divisions.[1] The International Hydrographic Organization (IHO) recognizes it as an
ocean, although some oceanographers call it the Arctic Mediterranean Sea or simply
the Arctic Sea, classifying it as one of the mediterranean seas of the Atlantic Ocean.
[2] Alternatively, the Arctic Ocean can be seen as the northernmost lobe of the all-
encompassing World Ocean.
Almost completely surrounded by Eurasia and North America, the Arctic Ocean is
partly covered by sea ice throughout the year[3] (and almost completely in winter).
The Arctic Ocean's temperature and salinity vary seasonally as the ice cover melts andfreezes;[4] its salinity is the lowest on average of the five major oceans, due to low
evaporation, heavy freshwater inflow from rivers and streams, and limited connection
and outflow to surrounding oceanic waters with higher salinities. The summer
shrinking of the ice has been quoted at 50%.[1] The National Snow and Ice Data
Center (NSIDC) uses satellite data to provide a daily record of Arctic sea ice cover
and the rate of melting compared to an average period and specific past years.