Continental Divide of the Americas

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The Continental Divide in North America in red, among other major hydrological divides. NorthAmerica-WaterDivides.png
The Continental Divide in North America in red, among other major hydrological divides.
The Continental Divide in Central America and South America. SouthAmerica-ContinentalDivide.png
The Continental Divide in Central America and South America.

The Continental Divide of the Americas (also known as the Great Divide, the Western Divide or simply the Continental Divide; Spanish : Divisoria continental de América, Gran Divisoria) is the principal, and largely mountainous, hydrological divide of the Americas. The Continental Divide extends from the Bering Strait to the Strait of Magellan, and separates the watersheds that drain into the Pacific Ocean from those river systems that drain into the Atlantic Ocean (including those that drain into the Gulf of Mexico and the Caribbean Sea) and, along the northernmost reaches of the Divide, those river systems that drain into the Arctic Ocean and Hudson Bay.

Contents

Although there are many other hydrological divides in the Americas, the Continental Divide is by far the most prominent of these because it tends to follow a line of high peaks along the main ranges of the Rocky Mountains and Andes, at a generally much higher elevation than the other hydrological divisions.

Geography

The Continental Divide in the Front Range of the Rocky Mountains of north central Colorado, taken from the International Space Station on October 28, 2008 GrtDivideCO.jpg
The Continental Divide in the Front Range of the Rocky Mountains of north central Colorado, taken from the International Space Station on October 28, 2008

The Continental Divide begins at Cape Prince of Wales, Alaska, the westernmost point on the mainland of the Americas. The Divide crosses northern Alaska into the Yukon, then zig-zags south into British Columbia via the Cassiar Mountains and Omineca Mountains and northern Nechako Plateau to Summit Lake, north of the city of Prince George and just south of the community of McLeod Lake. From there the Divide traverses the McGregor Plateau to the spine of the Rockies, following the crest of the Canadian Rockies southeast to the 120th meridian west, from there forming the boundary between southern British Columbia and southern Alberta.

Grays Peak, here in mid-June 2007, at 4,352 m (14,278 ft) it is the highest point of the Continental Divide in North America. Grays Peak, Colorado - 2007-06-17.jpg
Grays Peak, here in mid-June 2007, at 4,352 m (14,278 ft) it is the highest point of the Continental Divide in North America.
Historically, the Continental Divide was the line between British and US land possession in the disputed Oregon Country. Oregoncountry2.png
Historically, the Continental Divide was the line between British and US land possession in the disputed Oregon Country.

The Divide crosses into the United States in northwestern Montana, at the boundary between Waterton Lakes National Park and Glacier National Park. In Canada, it forms the western boundary of Waterton Lakes National Park, and in the US bisects Glacier National Park. Further south, the Divide forms the backbone of the Rocky Mountain Front (Front Range) in the Bob Marshall Wilderness, heads south towards Helena and Butte, then west past the namesake community of Divide, Montana, through the Anaconda-Pintler Wilderness to the Bitterroot Range, where it forms the eastern third of the state boundary between Idaho and Montana. The Divide crosses into Wyoming within Yellowstone National Park and continues southeast around the Great Divide Basin, through the Sierra Madre Range into Colorado where it reaches its highest point in North America at the summit of  Grays Peak at 4,352 m (14,278 feet).[ citation needed ] It crosses US Hwy 160 in southwestern Colorado at Wolf Creek Pass, where a line symbolizes the division. The Divide then proceeds south into western New Mexico, passing along the western boundary of the endorheic Plains of San Agustin. Although the Divide represents the height of land between watersheds, it does not always follow the highest ranges/peaks within each state or province.

The Parting of the Waters in the Teton Wilderness. One fork flows to the Pacific Ocean while the other flows to the Atlantic. Two oceans parting.JPG
The Parting of the Waters in the Teton Wilderness. One fork flows to the Pacific Ocean while the other flows to the Atlantic.

In Mexico, it passes through Chihuahua, Durango, Zacatecas, Aguascalientes, Jalisco, Guanajuato, Querétaro, México, the Federal District, Morelos, Puebla, Oaxaca, and Chiapas. In Central America, it continues through southern Guatemala, southwestern Honduras, western Nicaragua, western/southwestern Costa Rica, and southern Panama. The divide reaches its lowest natural point in Central America at the Isthmus of Rivas at 47 m (154 feet) in Nicaragua. In Panama, the Canal cuts through it at 26 m (85 ft).

The Divide continues 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, another, mainly non-mountainous divide, the Laurentian Divide (or Northern Divide), further separates the Hudson Bay-Arctic Ocean drainage region from the Atlantic watershed region. Secondary divides separate the watersheds that flow into the Great Lakes and Saint Lawrence River (ultimately into the Atlantic) from watersheds that flow to the Atlantic via the Missouri-Mississippi complex. Another secondary divide follows the Appalachian chain, which separates those streams and rivers that flow directly into the Atlantic Ocean from those that exit via the Mississippi River.

Triple points

Triple Divide Peak in Glacier National Park, Montana, is the point where two of the principal continental divides in North America converge, the primary Continental Divide and the Northern or Laurentian Divide. From this point, waters flow to the Pacific Ocean, the Atlantic Ocean via the Gulf of Mexico, and the Arctic Ocean via Hudson Bay. Most geographers, geologists, meteorologists, and oceanographers consider this point the hydrological apex of North America, as Hudson Bay is generally considered part of the Arctic. For example, the International Hydrographic Organization (in its current unapproved working edition only [1] of Limits of Oceans and Seas) defines the Hudson Bay, with its outlet extending from 62.5 to 66.5 degrees north (just a few miles south of the Arctic Circle) as being part of the Arctic Ocean, specifically "Arctic Ocean Subdivision 9.11."

This hydrological apex of North America status of Triple Divide Peak is the main reason behind the designation of Waterton-Glacier International Peace Park as the "Crown of the Continent" of North America. [2] The summit of the peak is the world's only oceanic triple divide point. [3] Discounting Antarctica and its ice sheets, only one other continent (Asia) borders three oceans, but the inward-draining Endorheic basin area of Central Asia from western China to the Aral and Caspian Seas is so vast that any Arctic and Indian Ocean tributaries are never within proximity of each other. [3] Thus, North America's status of having a single location draining into three oceans is unique in the world.

Sources differ, however, on whether Hudson Bay, entirely south of the Arctic Circle, is part of the Atlantic or Arctic Ocean. [4] Hudson Bay's water budget connects to the Atlantic more than to the Arctic Ocean. [5] The channels to the north of Hudson Bay are largely cut off by Baffin Island from the Arctic, so much of the water that enters it mixes with the Atlantic to the east via Hudson Strait rather than north into the Arctic. The result is that most of the ice flowing down the Saskatchewan Glacier eventually ends up as water in the Atlantic Ocean. [6] [7]

If Hudson Bay is considered part of the Atlantic, then the triple point is at an unimportant-looking, permanently snow and ice covered hump on the border between Alberta and British Columbia, on the southern slope of Snow Dome at 3,456 metres (11,300 ft). The exact location of this potential triple point is somewhat indeterminate because the Columbia Icefield and the snow on top of it shifts from year to year. The snow that falls on it (about 10 metres (33 ft) per year) does not actually flow downhill as water, but creeps downhill in the form of glacial ice.

That ice flows down the Athabasca Glacier to the Arctic Ocean via the Athabasca and Mackenzie rivers. Ice flowing west goes to the Pacific Ocean via Bryce Creek and the Bush and Columbia Rivers. Ice flowing down the Saskatchewan Glacier goes via the North Saskatchewan, Saskatchewan, and Nelson rivers into Hudson Bay. [8]

While Triple Divide Peak (or, alternatively, Snow Dome) is the world's only oceanic triple divide, there are secondary triple divide points wherever any two continental divides meet. North America has five major drainage systems: into the Pacific, Atlantic and Arctic oceans, plus Hudson Bay and the Gulf of Mexico. Other sources such as the International Hydrographic Organization add a sixth: Canada's Northwest Passage basin. Using just the five, there are four secondary continental divides and three secondary triple points, the two mentioned previously and a third near Hibbing, Minnesota, where the Northern Divide intersects the Saint Lawrence Seaway divide. [9] Since there is no true consensus on what a continental divide is, there is no real agreement on where the secondary triple points are located. [10] 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 often remains above the treeline and on the Divide, providing unobstructed views along its route. Montana CDT.jpg
The Continental Divide Trail often remains above the treeline and on the Divide, providing unobstructed views along its route.

Hiking trail

The Continental Divide Trail (CDT) follows the Divide through the U.S. from the Mexico–US border to the Canada–US border. The trail itself is a corridor of pathways - i.e. dedicated footpaths or back roads, either on or near the Continental Divide. A less-developed Canadian extension called the Great Divide Trail continues through five national parks and six provincial parks, ending at Kakwa Lake in east-central British Columbia. [11]

Exceptions

Many endorheic regions in North and South America complicate the simple view of east or west, "ocean-bound" water flow. Several endorheic basins straddle or adjoin the Continental Divide, notably the Great Divide Basin in Wyoming, the Plains of San Agustin and the Animas Valley in New Mexico, the Guzmán Basin in New Mexico and Chihuahua, Mexico, and both the Bolsón de Mapimí and the Llanos el Salado in Mexico. Such basins can be, and routinely are, assigned to one side of the Divide or the other by their lowest perimeter pass; in other words, an assignment is made by determining how the drainage would occur if the basin were to be progressively filled with water until it overflowed. Large-scale maps, such as those on this page, often show double divide lines when endorheic basins are involved. However, the detailed USGS topographic maps of the United States generally show only the main Divide as determined by the overflow rule. Among other things, this eliminates the need to trace out the boundary for a basin that is very shallow and has a nebulous rim, such as the San Luis Closed Basin in Colorado and the sink of the lost streams of Idaho.

Another rare exception occurs when a stream near a divide splits and flows in both directions, or a lake straddling the divide overflows in both directions. Examples of these are, respectively, North Two Ocean Creek and Isa Lake, both located on the Continental Divide in Wyoming. The Panama Canal has this same feature, but is man-made. Both the Chagres and Gatun rivers flow into Gatun Lake, which empties to both oceans.

Several small lakes along the Divide in the Rocky Mountains between Alberta and British Columbia flow into both provinces and thus into both Atlantic and Pacific Oceans. An example is the "Committee's Punch Bowl", a small lake located in the Athabasca Pass. [lower-alpha 1]

The Alpine Club of Canada's Abbot Pass Hut sits directly astride the Divide in Abbot Pass on the boundary between Banff National Park and Yoho National Park, and thus rainwater falling on the eastern half of the roof flows via Lake Louise into Hudson Bay, while rain falling on the western half flows via Lake O'Hara into the Pacific Ocean.

See also

Continental divides

Note

  1. It was named by George Simpson, governor of the Hudson's Bay Company, while touring his vast Canadian fur-trading empire in 1825. According to historical sources, "The small circular basin of water at the summit, twenty yards in diameter, is dignified with the name of the 'Committee's Punch Bowl' in honour of which the Governor treated them (his fur traders) to a bottle of wine as they had 'neither time nor convenience to make a bowl of punch, although a glass of it would have been acceptable.'" The reference is to the governing committee of the Hudson's Bay Company in London, England. [12]

Related Research Articles

Geography of Canada Geographic features of Canada

Canada has a vast geography that occupies much of the continent of North America, sharing land borders with the contiguous United States to the south and the U.S. state of Alaska to the northwest. Canada stretches from the Atlantic Ocean in the east to the Pacific Ocean in the west; to the north lies the Arctic Ocean. Greenland is to the northeast and to the southeast Canada shares a maritime boundary with France's overseas collectivity of Saint Pierre and Miquelon, the last vestige of New France. By total area, Canada is the second-largest country in the world, after Russia. By land area alone, however, Canada ranks fourth, the difference being due to it having the world's largest proportion of fresh water lakes. Of Canada's thirteen provinces and territories, only two are landlocked while the other eleven all directly border one of three oceans.

Drainage basin Area of land where precipitation collects and drains off into a common outlet

A drainage basin is any area of land where precipitation collects and drains off into a common outlet, such as into a river, bay, or other body of water. The drainage basin includes all the surface water from rain runoff, snowmelt, hail, sleet and nearby streams that run downslope towards the shared outlet, as well as the groundwater underneath the earth's surface. Drainage basins connect into other drainage basins at lower elevations in a hierarchical pattern, with smaller sub-drainage basins, which in turn drain into another common outlet.

Endorheic basin Closed drainage basin that allows no outflow

An endorheic basin is a drainage basin that normally retains water and allows no outflow to other external bodies of water, such as rivers or oceans, but converges instead into lakes or swamps, permanent or seasonal, that equilibrate through evaporation. They are also called closed or terminal basins or internal drainage systems or basins. Endorheic regions contrast with exorheic regions. Endorheic water bodies include some of the largest lakes in the world, such as the Caspian Sea, the world's largest inland body of water.

Canadian Rockies Mountain range in Canada

The Canadian Rockies or Canadian Rocky Mountains comprise both the Alberta Rockies and the B.C. Rockies in the Canadian segment of the North American Rocky Mountains. They are the eastern part of the North American Cordillera, which is a system of multiple ranges of mountains which runs from the Prairies to the Pacific Coast. The Canadian Rockies mountain system comprises the southeastern part of this system, lying between the Interior Plains of Alberta and northeastern British Columbia on the east to the Rocky Mountain Trench of BC on the west. The southern end borders Idaho and Montana of the United States. In geographic terms, the boundary is at the Canada–United States border, but in geological terms it might be considered to be at Marias Pass in northern Montana. The northern end is at the Liard River in northern British Columbia.

Eastern Continental Divide Hydrological divide in eastern North America

The Eastern Continental Divide or Eastern Divide or Appalachian Divide is a hydrographic divide in eastern North America that separates the easterly Atlantic Seaboard watershed from the westerly Gulf of Mexico watershed. The divide nearly spans the United States from south of Lake Ontario through the Florida peninsula, and consists of raised terrain including the Appalachian Mountains to the north, the southern Piedmont Plateau and lowland ridges in the Atlantic Coastal Plain to the south. Water including rainfall and snowfall, lakes, streams and rivers on the eastern/southern side of the divide drains to the Atlantic Ocean; water on the western/northern side of the divide drains to the Gulf of Mexico. The ECD is one of six continental hydrographic divides of North America which define several drainage basins, each of which drains to a particular body of water.

Columbia Icefield

The Columbia Icefield is the largest ice field in North America's Rocky Mountains. Located within the Canadian Rocky Mountains astride the Continental Divide of the Americas along the border of British Columbia and Alberta, Canada, the ice field lies partly in the northwestern tip of Banff National Park and partly in the southern end of Jasper National Park.

Triple Divide Peak (Montana)

Triple Divide Peak is located in the Lewis Range, part of the Rocky Mountains in North America. The peak is a feature of Glacier National Park in the state of Montana in the United States. The summit of the peak, the hydrological apex of the North American continent, is the point where two of the principal continental divides in North America converge, the Continental Divide of the Americas and the Northern or Laurentian Divide.

Snow Dome (Canada)

Snow Dome is a mountain located on the Continental Divide in the Columbia Icefield, where the boundary of Banff National Park and Jasper National Park meets the border of Alberta and British Columbia in Canada. The summit's elevation is 3,456 m (11,339 ft).

Hudson Bay drainage basin drainage basin in Canada which empties into Hudson Bay

The Hudson Bay drainage basin is the drainage basin in northern North America where surface water empties into Hudson Bay and adjoining waters. Spanning an area of about 3,861,400 square kilometres (1,490,900 sq mi), the basin is almost totally in Canada, with a small portion in the United States . The watershed's connection to the Labrador Sea is at the Hudson Strait's mouth between Resolution Island in the Qikiqtaaluk Region and Cape Chidley on the Labrador Peninsula. The watershed's headwaters to the southwest are on the Continental Divide of the Americas, bounded at Triple Divide Peak to the south, and Snow Dome to the north. The western and northern boundary of the watershed is the Arctic Divide, and the southern and eastern boundary is the Laurentian Divide.

Laurentian Divide Hydrological divide in North America

The Laurentian Divide also called the Northern Divide and locally the height of land, is a continental divide in central North America that separates the Hudson Bay watershed to the north from the Gulf of Mexico watershed to the south and the Great Lakes-St. Lawrence watershed to the southeast.

Traverse Gap

The Traverse Gap is an ancient river channel occupied by Lake Traverse, Big Stone Lake and the valley connecting them at Browns Valley, Minnesota. It is located on the border of the U.S. states of Minnesota and South Dakota. Traverse Gap has an unusual distinction for a valley: it is crossed by a continental divide, and in some floods water has flowed across that divide from one drainage basin to the other. Before the Anglo-American Convention of 1818 it marked the border between British territory in the north and U.S. – or earlier, French – territory in the south.

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 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.

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 is unconnected. Continental divide may also refer to:

Watersheds of North America

Watersheds of North America are large drainage basins which drain to separate oceans, seas, gulfs, or endorheic basins. There are six generally recognized hydrological continental divides which divide the continent into seven principal drainage basins spanning three oceans and one endorheic basin. The basins are the Atlantic Seaboard basin, the Gulf of Mexico basin, the Great Lakes-St. Lawrence basin, the Pacific basin, the Arctic basin, the Hudson Bay basin, and the Great Basin. Together, the principal basins span the continent with the exception of numerous smaller endorheic basins.

Triple divide Point where three drainage basins meet

A triple divide or triple watershed is a point on the Earth's surface where three drainage basins meet. A triple divide results from the intersection of two drainage divides. Triple divides range from prominent mountain peaks to minor side peaks, down to simple slope changes on a ridge which are otherwise unremarkable. The elevation of a triple divide can be thousands of meters to barely above sea level. Triple divides are a common hydrographic feature of any terrain that has rivers, streams and/or lakes.

Saint Lawrence River Divide hydrological divide in eastern North America


The Saint Lawrence River Divide is a continental divide in central and eastern North America that separates the Great Lakes-St. Lawrence River Basin from the southerly Atlantic Ocean watersheds. Water, including rainfall and snowfall, lakes, rivers and streams, north and west of the divide, drains into the Gulf of St. Lawrence or the Labrador Sea; water south and east of the divide drains into the Atlantic Ocean or Gulf of Mexico. The divide is one of six continental divides in North America that demarcate several watersheds that flow to different gulfs, seas or oceans.

References

  1. "IHO Publication S-23 Limits of Oceans and Seas; Chapter 9: Arctic Ocean". International Hydrographic Organization. 2002. Archived from the original on 2014-02-02. Retrieved 2017-07-01.
  2. "State of Flathead Lake". University of Montana Flathead Lake Biological Station. Retrieved 2015-09-28.
  3. 1 2 "Ocean Triple Divide Points". Peakbagger.com. Retrieved 2017-07-01.
  4. Sanford, Robert W. (2010). Our World's Heritage: Creating a Culture Worthy of Place in Canada's Western Mountain Parks. Athabasca University Press. p. 160. ISBN   978-1-897425-57-2.
  5. Lewis, Edward Lyn; Jones, E. Peter; et al., eds. (2000). The Freshwater Budget of the Arctic Ocean. Springer. p. 101. ISBN   978-0-7923-6439-9 . Retrieved 26 November 2010.
  6. Timmer, Henry (2006). "Snow Dome - The Hydrological Apex of North America". Snow Dome. climbwild.net. Archived from the original on 2007-10-25. Retrieved 2007-12-28.
  7. Timmer, Henry. "The Columbia Icefield". climbwild.net. Archived from the original on 2014-08-10. Retrieved 2014-07-30.
  8. "Snow Dome-South Slope, British Columbia". Peakbagger. Retrieved 2015-09-28.
  9. monica driscollian rivers atlas (2006). "Minnesota Rivers Map". Minnesota State Map Collection. Geology.com. Retrieved 2007-12-29.
  10. Gonzalez, Mark A. (2002). "Continental Divides in North Dakota and North America" (PDF). NGDS Newsletter. North Dakota Geological Survey. Archived from the original (PDF) on 2013-01-17. Retrieved 2007-12-29.
  11. Lynx, Dustin (2000). Hiking Canada's Great Divide Trail. Rocky Mountain Books. ISBN   0-921102-79-8. Archived from the original on 2016-03-16. Retrieved 2010-04-08.
  12. GeoBC (2013). "Committee Punch Bowl". gov.bc.ca. Province of British Columbia. Retrieved 2014-09-29.