CONTINENTAL DIVIDE
A continental
divide is a drainage divide on
a continent such
that the drainage basin on
one side of the divide feeds into one ocean or sea,
and the basin on the other side either feeds into a different ocean or sea, or
else is endorheic, not connected to the open sea.
The endpoints where a continental divide meets the coast
are not always definite, because the exact border between adjacent bodies of
water is usually not clearly defined. TheInternational
Hydrographic Organization's publication Limits of Oceans and Seas defines exact boundaries of oceans,
but it is not universally recognized. Where a continental divide meets an
endorheic basin, such as the Great Divide Basin of Wyoming, the continental divide splits and encircles the
basin.
Examples
·
In Africa,
the most significant continental divide is the Congo-Nile Divide between
the watersheds of the Nile and the Congo, passing through the area of the African Great Lakes.
Between the Congo and the Sahara,
a vast area drains into the endorheicLake Chad, so puncturing the Atlantic–Mediterranean divide. The Mediterranean–Indian Ocean divide
is punctured in East Africaby the endorheic lake systems of the East African Rift; in the south of the continent the divide
between the Atlantic and Indian Oceans snakes between the watersheds of the
Congo, Zambezi, Limpopo and Orange Rivers, with the Okavango terminating
in the Kalahari Desert.
·
The interior of Antarctica receives
very little precipitation, and that in the form of snow,
and the continent is surrounded by theSouthern Ocean. Therefore, Antarctica is not generally
considered to have a continental divide. The Transantarctic Mountainsdivide
the ice streams draining West Antarctica into
the Ronne Ice Shelf, toward the Pacific and into
the Ross Ice Shelf, from those draining East Antarctica toward
the Atlantic and Indian Oceans.
·
In Australia the Great Dividing Range largely separates those rivers flowing
to the eastern seaboard and the Pacific Ocean from those flowing westward to
the Murray–Darling Basin and to the Southern Ocean. However, Australia has fewer distinct ocean
boundaries and fewer prominent mountain ranges, which makes it hard to clearly
and precisely define any one divide. Much of the interior of the continent
drains into the endorheic Lake Eyre Basin.
·
Eurasia has various divides, depending on the definition of
"ocean" (for example, the Mediterranean Sea and
its various lobes, theAtlantic Ocean, the Arctic Ocean, the Baltic Sea, the Black Sea, and the North Sea). Examples include:
·
Asia:
·
Himachal Pradesh (Sutlej–Indus): Arabian Sea
·
Lake Baikal (Yenisei–Lena): Kara Sea, Laptev Sea
·
Perm Krai/Urals (Volga–Pechora/Ob): Caspian Sea, Arctic Sea
·
Uttarakhand (Yamuna–Ganges): Bay of Bengal
·
Europe-Asia:
·
Don-Volga: Black Sea, Caspian Sea
·
Europe:
·
the European Watershed with the triple divide of North Sea (Rhine),
Black Sea (Danube) and Mediterranean Adriatic Sea (Po) at Lunghin Pass in
the Central Eastern Alps.
·
North America
·
The Arctic Divide, in conjunction with other
continental divides of North America, demarcates two watersheds of the Arctic Ocean: the Arctic Ocean watershed and theHudson Bay watershed. This divide was a barrier
to transportation until the Methye Portage was
discovered in 1778, which opened up the Arctic rivers to the fur tradersand became part of a transcontinental trade route
from Atlantic to Pacific. It was of significance in Canadian history because it
marked the northern boundary of Rupert's Land, the trading monopoly area of
the Hudson's Bay Company.[1]
·
The Continental Divide of the
Americas, also called the Great Divide, separates the watersheds of
the Pacific Ocean from
those of the Atlantic and Arctic Oceans. It runs from the Seward Peninsula in Alaska,
through western Canada along the crest of the Rocky Mountains, including through Glacier National Park, Yellowstone National Park,
and Rocky Mountain National Park to New Mexico. From there, it follows the crest of Mexico's Sierra Madre Occidental and extends to the tip of South America. It is crossed by the Panama Canal and
by the two outlets of Isa Lake in
Yellowstone National Park.
·
The Eastern Continental Divide separates the watershed of the Gulf of Mexico from
the Atlantic Ocean. It runs from the Twin Tiers of New York and Pennsylvania along
theAppalachian Mountains to the tip of Florida. The city of Atlanta sits
atop this divide.
·
The Northern Divide, or Laurentian Divide, separates the watershed of the Atlantic Ocean from
that of Hudson Bay. The western part of it from Glacier National Park
in the Rocky Mountains to the Great Lakes watershed marked the northern
boundary of the Louisiana Purchase and was the border between the United
States and British North America until it was superseded by the 49th parallel in the treaty of 1818. In Canada, it historically marked the southern
boundary of the fur trading monopoly area of theHudson's Bay Company, and
the easternmost portion still marks part of the boundary between Quebec and Labrador. The divide traverses very flat terrain, especially
in North Dakota, causing many travelers to believe the sign marking the divide
is a joke.[2]
·
The St. Lawrence River Divide separates the Great Lakes Basin from
the rest of the Atlantic Ocean watershed. Two canals cross the divide: The Chicago Sanitary and Ship Canal crosses the Chicago Portage and
connects Lake Michigan to
the Mississippi River watershed.
The Erie Canal connects Lake Erie to the Hudson River watershed.
Historically there were additional canals, e.g., the Ohio and Erie Canal, but
most of these are no longer in operation.
·
In South America, the Continental Divide of the
Americas lies along
the Andes,
from Lácar Lake and
south there are numerous lakes on the eastern slopes that drains to the
Pacific, crossing the line of highest peaks. These lakes in Patagonia are
moraine-dammed streams that used to drain to the Atlantic rather than the
Pacific before thePleistocene glaciations.
REFERENCE
http://en.wikipedia.org/wiki/Continental_divide
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