Continental divide

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Major continental divides, showing drainage into the major oceans and seas of the world. Grey areas are endorheic basins that do not drain to the ocean.

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. Every continent on earth except Antarctica (which has no known significant, definable free-flowing surface rivers) has at least one continental drainage divide; islands, even small ones like Killiniq Island on the Labrador Sea in Canada, may also host part of a continental divide or have their own island-spanning divide. The endpoints of a continental divide may be coastlines of gulfs, seas or oceans, the boundary of an endorheic basin, or another continental divide. One case, the Great Basin Divide, is a closed loop around an endorheic basin. The endpoints where a continental divide meets the coast are not always definite since the exact border between adjacent bodies of water is usually not clearly defined. The International 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. Where two divides intersect, they form a triple divide, or a tripoint, a junction where three watersheds meet.

Whether a divide is considered a continental divide distinguished from other secondary drainage divides may depend on whether the associated gulfs, seas, or oceans are considered separate. For example, the Gulf of Mexico is considered separate from the Atlantic Ocean, so the Eastern Continental Divide separates their respective watersheds. But the

Sea of Cortez
is usually not considered separate from the Pacific Ocean, so the divide between the Colorado River watershed, which drains to the Sea of Cortez, and the Columbia River watershed, which drains to the Pacific Ocean, is not considered to be a continental divide.

Together, continental divides demarcate a set of drainage basins or watersheds, each of which drains to a specific ocean, sea or gulf, such as the North American Atlantic seaboard watershed which is demarcated by the Eastern Continental Divide and Great Lakes-St. Lawrence Divide.

Divides by continent

Note: A 'continent' for the purpose of water divides may not correspond to a geopolitical or geophysical continent.

Africa

In

Mediterranean divide. The Mediterranean–Indian Ocean divide is punctured in East Africa by 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
.

Antarctica

Ronne Ice Shelf, toward the Pacific Ocean and into the Ross Ice Shelf, from those draining East Antarctica
toward the Atlantic and Indian Oceans.

Australia

In

Lake Eyre Basin
, which during previous Ice Ages was a much larger sea.

Eurasia

Eurasia has various divides, depending on the definition of "ocean" (for example, the Mediterranean Sea and its various lobes, the Atlantic Ocean, the Arctic Ocean, the Baltic Sea, the Black Sea, and the North Sea). Examples include:

British Isles

North America

hydrological divides of North America
.

If the Gulf of California or Sea of Cortez is considered to be separate from the Pacific Ocean, there is a divide which separates the Pacific Ocean basin from the basin which drains into that gulf/sea, i.e the Colorado River basin:

South America

In South America, the Continental Divide of the Americas lies along the Andes. In Central Chile and nearby areas of Argentina the Principal Cordillera makes up the continental divide.[6] This divide forms much of the Argentina–Chile border. In the Miocene the continental divide in the Principal Cordillera was about 20 km to the west of the modern water divide.[7] Subsequent river incision shifted the divide to the east.[7] Compression and uplift in this part of the Andes has continued into the present.[7]

From

glaciations.[citation needed
]

See also

  • Bioceanic principle
  • Cordillera de los Andes
    forming part of the Continental Divide of the Americas in South America
  • Royal Proclamation of 1763 which followed the Eastern Continental Divide
  • Louisiana Purchase whose northern boundary was the Laurentian Divide
  • Treaty of 1818 which redefined the U.S./ British Canadian boundary west of the Great Lakes from the Laurentian Divide to the 49th parallel

References

  1. ^ "Kennedy Junction". Australian Extremes. March 18, 2021. Retrieved March 18, 2021.
  2. ^ In Europe and internationally, divides are called 'watersheds'.
  3. ^ Latin for "unknown limits"
  4. ^ Foster, John E.; Eccles, W.J. (1985). "Fur Trade". The Canadian Encyclopedia. The Historica Foundation of Canada. Retrieved 2007-12-30.
  5. ^ Gonzalez, Mark (2007). "Continental Divides in North Dakota and North America" (PDF). NDGS Newsletter. North Dakota Geographical Society. Archived from the original (PDF) on 2013-01-17. Retrieved 2009-03-29.
  6. ^ "Orografía de Mendoza". El Portal de Mendoza (in Spanish). Cámara de Turismo de Mendoza and Cooperativa El Portal de Mendoza. Retrieved June 29, 2019.
  7. ^ . Retrieved June 9, 2019.

External links