Continental Divide (Atlantic/Pacific)


Continental Divide (Atlantic/Pacific)

:"For continental divides in general, see Continental Divide."
[


thumb|300px|Continental divides in North America. The Great Divide is in red.]

Continental Divide or Great Divide is the name given to the North American portion of the mountainous ridge which separates the watersheds that drain into the Pacific Ocean from, 1) those river systems which drain into the Atlantic Ocean (including those which drain via the Gulf of Mexico), and 2) along the northernmost reaches of the Divide, those river systems which drain into the Arctic Ocean. A secondary, non-mountainous divide further separates other river systems that drain into the Arctic Ocean (including those which drain via Hudson Bay, James Bay, and Ungava Bay) from those which drain into the Atlantic Ocean (including those which drain via the Great Lakes and Saint Lawrence Seaway).

Geography

The divide begins at Cape Prince of Wales in Alaska. It runs northeast-/eastward across the north of the state into the Yukon Territory, Canada, where it turns south and travels through British Columbia (forming part of the B.C.-Alberta boundary), in Canada; then through Montana (forming part of the Montana-Idaho boundary), Wyoming, Colorado, and New Mexico, in the United States; then along the crest of the Sierra Madre Occidental through the Mexican states of Chihuahua, Durango, Zacatecas, Aguascalientes, Jalisco, Guanajuato, Querétaro, México, the Federal District, Morelos, Puebla, Oaxaca, and Chiapas; thence through southern Guatemala, southwestern Honduras, western Nicaragua, and western/southwestern Costa Rica, and southern Panama.

The physical divide continues (though the name "Great Divide" does not) into South America, where it follows the peaks of the Andes Mountains, traversing western Colombia, central Ecuador, western and southwestern Peru, and eastern Chile (essentially conforming to the Chile-Bolivia and Chile-Argentina boundaries), southward to the southern end of Patagonia and Tierra del Fuego.

In North America, Triple Divide Peak in Glacier National Park, in Montana, is the point at which two of the principal continental divides in North America converge, the Great Divide and the Northern Divide. From this point, waters flow to the Pacific, the Atlantic and the Arctic Oceans. Another triple divide or "triple point" occurs in Canada on a prominent peak directly on the border between Alberta and British Columbia, called Snow Dome because the Columbia Icefield completely covers the summit. [cite web
last = Birrel
first = Dave
title = Snow Dome
work = Peaks of the Canadian Rockes
publisher = PeakFinder (Rocky Mountain Books)
date = 2007
url = http://peakfinder.com/peakfinder.ASP?PeakName=Snow+Dome
accessdate = 2007-12-28
] Water flows off this mountain into the Pacific, via the Columbia River system; the Arctic via the Athabasca River and MacKenzie River systems; and Hudson Bay via the North Saskatchewan River system. Because Canadians consider Hudson Bay to be an extension of the Atlantic Ocean, they consider Snow Dome to be the hydrological apex of North America. [cite web
last = Timmer
first = Henry
title = Snow Dome - The Hydrological Apex of North America
work = Snow Dome
publisher = climbwild.net
date = 2006
url = http://climbwild.net/MP_Snow_Dome_page_one.html
accessdate = 2007-12-28
]

In fact, there are such triple divide points wherever two continental divides meet. [cite web
last = Andersen
first = Robert N.
title = Triple Divide Points and North American Drainage Basins
publisher = University of Wisconsin - Eau Claire
date = 2006
url = http://www.uwec.edu/andersrn/Triple_Divide_Pts.htm
accessdate = 2007-12-29
] North America can be considered to have five major drainage systems: into the Pacific, Atlantic and Arctic Oceans, plus Hudson Bay and the Gulf of Mexico. Within this system there are four continental divides and three triple points, the two mentioned previously and a third near Hibbing, Minnesota where the Northern Divide intersects the Eastern Continental Divide. [cite web
last =
first =
chapter = Minnesota Rivers Map
title = Minnesota State Map Collection
publisher = Geology.com
date = 2006
url = http://geology.com/state-map/minnesota.shtml
accessdate = 2007-12-29
] Since there is no true consensus on what a continental divide is, there is no real agreement on where the triple points are. [cite web
last = Gonzalez
first = Mark A.
title = Continental Divides in North Dakota and North America
work = NGDS Newsletter
publisher = North Dakota Geological Survey
date = 2002
url = https://www.dmr.nd.gov/ndgs/Newsletter/NLS03/pdf/Divide.pdf
accessdate = 2007-12-29
] However, the main Continental Divide described in this article is a far more distinctive geological feature than the others and its two main triple points are much more prominent.

The Continental Divide Trail follows the divide through the U.S. from the Mexican border to the Canadian border. A less-developed Canadian extension called the Great Divide Trail continues on through five National Parks of Canada and six provincial parks to end at Kakwa Lake in northeastern British Columbia. [cite book
last = Lynx
first = Dustin
title = Hiking Canada's Great Divide Trail
publisher = Rocky Mountain Books
date = 2000
url = http://rmbooks.com/books/lynhik.htm
isbn = 0921102798
]

Exceptions

Many endorheic regions in North America complicate the simple view of east or west, "ocean-bound" water flow.

The Great Basin of the Western US, The Valley of Mexico and Bolson de Mapimi in Mexico, the Tularosa Basin in New Mexico and Texas, and the Salton Trough are examples of internally draining areas. In these cases, water often drains to low basins, where sedimentation and evaporation form salt lakes, playas, salt flats, and alkali flats.

On the Llano Estacado in Texas and New Mexico, many thousands of seasonal playa lakes form during wet months, an average of one per square mile. This region is very flat, and water mostly evaporates before draining.

Zuni Salt Lake is one example of a larger, seasonal maar which does not drain to an ocean. There are a number of seasonal lakes of this sort in North America. In areas of karst topography (such as northern Florida), isolated drainages can also occur.

The Great Divide Basin in Wyoming has no natural outlet except as groundwater, and hence it lies between the Atlantic and Pacific watersheds, being part of neither. Water from the North Two Ocean Creek in Wyoming flows into both oceans.

Additionally, although Panama's isthmus provides clear division between Atlantic and Pacific, the boundaries between the Atlantic and Arctic Oceans in Baffin Bay are not well defined, rendering the easternmost portion of this divide arbitrary.


=

References

ee also

*Northern Divide (Laurentian Divide}
*Eastern Continental Divide
*List of railroad crossings of the North American continental divide
*Laurentia
*Continental Divide Trail
*Great Divide Trail
*Valparaiso Moraine
*Lemhi Pass

External links

* [http://www.cec.org/naatlas/watersheds.cfm?varlan=english A detailed map of watersheds in North America]
* [http://www.fws.gov/nwi/Pubs_Reports/isolated/report_files/2_section/overview.htm A detailed overview of isolated wetlands from the USFWS]
* [http://nationalatlas.gov/articles/geology/a_continentalDiv.html Detailed article, maps, and boundary data] from "The National Atlas of the United States"
* [http://www.geocities.com/Heartland/Garden/9907/2OP/ Parting of the Waters: a creek that flows to two oceans]


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