North American Continental Divide

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The North American Continental Divide, known as the Great Divide or the Western Divide, is an impressive landform running through the Americas. From its northernmost reaches in Alaska to its southern end at the Straits of Magellan, the North American Continental Divide separates the watersheds that flow into the Pacific Ocean and those that flow into the Gulf of Mexico and the Atlantic, Caribbean, and Arctic Oceans. 

Map of the Continental Divides in North America. Map: Pfly , CC BY-SA 3.0, Wikipedia.
Map of the Continental Divides in North America. Map: Pfly , CC BY-SA 3.0, Wikipedia.

The Great Divide is characterized by rivers that flow in opposite directions, some flowing thousands of miles before they reach their final destination.

Continental divides are essential parts of the water cycle that create unique weather patterns, create roaring rivers and trickling streams, and nourish multiple habitat regions on their way to the oceans. 

What is a Continental Divide?

A continental divide, or drainage divide, is a boundary that separates watersheds flowing in two different directions (More: What is a Continental Divide?). These rivers can flow into oceans, bays, or seas.

Rivers that don’t flow into seas or oceans can flow into landlocked lakes or salt flats, which is common in desert areas. These are known as endorheic basins. These watersheds can contain bodies of water large and small, from rivers to lakes and more. 

View of the Continental Divide in Colorado. Photograph credit: Alexander Stephens, Bureau of Reclamation.
View of the Continental Divide in Colorado. Photograph credit: Alexander Stephens, Bureau of Reclamation, public domain.

The precipitation that falls on one side of a divide tends to flow back into the body of water on that side. For instance, rain that falls on the western side of the North American Continental Divide flows into the Pacific Ocean, while precipitation that falls on the eastern slopes of the same divide eventually finds its way into the bodies of water lying to the east. This can create regional weather patterns and affect how much precipitation falls on a place and in what form it takes (rain or snow). 

A continent can have more than one divide. North America is home to between three and five divides; the number is uncertain because, as an example, there are no agreed upon boundaries to where the Atlantic Ocean ends and the Gulf of Mexico begins. The boundaries of these ocean basins determine how many watersheds there are flowing into these unique bodies of water.

While some watersheds flow east or west, others can flow north to south. Waters that drain into the Arctic Ocean can flow north and northeast along their watershed boundary.

Every continent, with the exception of Antarctica, has a continental divide.

Sign marking the continental divide in Colorado.
Continental Divide sign high in Rocky Mountain National Park in the Front Range of the spectacular and high Rockies in north-central Colorado. Photo: Carole M. Highsmith, 2015. Public domain via Loc.gov.

Convening Watersheds

Glacier National Park is home to one unique geographic feature of the North American Continental Divide, landmarked by the aptly named Triple Divide Peak (elevation: 8,020 feet / 2,446 meter). This is the location where the Great Divide meets the Laurentian Divide, a continental divide that separates the waters flowing to the Pacific, to the Atlantic, and to the Arctic Oceans via Hudson Bay. This area is considered to be the hydrologic apex of North America.

Due to their elevation, continental divides can contain glaciers and icefields. These bodies of snow and ice can make determining the boundaries of a watershed a bit more difficult. Rather than water falling as rain or snow into a river, these glaciers and icefields contribute water to the water cycle via glacial ice at a much slower rate than other forms of precipitation. 

This broad open saddle called South Pass in Wyoming located on the continental divide is one of the high points along the Oregon, California, and Mormon Pioneer national historic trails. Photo: NPS, public domain.
This broad open saddle called South Pass in Wyoming located on the continental divide is one of the high points along the Oregon, California, and Mormon Pioneer national historic trails. Photo: NPS, public domain.

The North American Continental Divide runs from Cape Prince of Wales on the Bering Sea coast  of Alaska, down to the Canadian Rockies into the American Rockies, then south through Mexico, Central America, and finally to the impressive peaks of the South American Andes. While this boundary encompasses high elevations in order to separate watersheds, the tallest peaks in these ranges are often not the dividing watershed line. However, these locations are home to popular hiking and camping locations, a variety of wildlife, and other experiences that are hard to come by anywhere else.

National Parks

In North America, the tallest point on the Great Divide is Grays Peak in the Sierra Madre Range in Colorado. Western New Mexico is home to the Great Divide’s endorheic Plains of Saint Agustin. 

Person hiking on the Continental Divide National Scenic Trail in Colorado.
Person hiking on the Continental Divide National Scenic Trail in Colorado. The Continental Divide National Scenic Trail crosses Bureau of Land Management land in Colorado, Idaho, Montana, New Mexico, and Wyoming. Photo: Bob Wick, Bureau of Land Mangement. Public domain.

Encompassed within this impressive divide geography include Glacier National Park, Banff National Park, and the Continental Divide hiking trail that runs between the United States/Canada border and the border of the United States and Mexico.

The geography of continental divides often results in impressive peaks, beautiful alpine lakes, and stunning vistas that attract photographers, backpackers, visitors, and many others. 

Many roads intersect the North American Continental Divide, allowing visitors to take in the elevation and views along the way. Routes through Montana, Wyoming, and Colorado in the United States as well as in British Columbia and Alberta, Canada wind through the mountains, forests, and vistas of the divide.

The Alaska-Canada highway, the only route that is driveable from the Lower 48 to Alaska, also crosses the path of the Great Divide in the United States and Canada. These roads can often be difficult to drive due to inclement weather throughout the year, as well as lots of snow in the winter.

A sign marking the location of the North American Continental Divide in Yellowstone National Park.  Photo: NPS, public domain.
A sign marking the location of the North American Continental Divide in Yellowstone National Park. Photo: NPS, public domain.

For those that do cross the Continental Divide, don’t worry about missing it. Between road signs and national park signs, you’ll know when you’ve crossed the Continental Divide. Due to the winding nature of the roads, you’ll likely cross it a few times along your journey. 

Divided Waters

Wyoming is home to two special bodies of water that are located on the Great Divide. These lakes are called Isa Lake and North Two Ocean Creek. By merit of their locations on the Continental Divide, these lakes have river outflows that flow in opposite directions.

These lakes get enough water flowing into them via snow and rain that they can have two outgoing water sources and not run dry. This feature also occurs in the Canadian Rocky Mountains near Athabasca Pass. 

No matter where you are along the North American Continental Divide, the Great Divide, the Western Divide or the Continental Divide, there are plenty of opportunities to pull over, get out of the car, and take in this impressive geological feature that influences our lives in more ways than we can imagine. 

References

Continental divide. (n.d.). NPS.gov (U.S. National Park Service). https://www.nps.gov/glac/learn/education/continental_divide.htm

Continental Divide National Scenic Trail. (n.d.). US Forest Service. https://www.fs.usda.gov/managing-land/trails/cdt

Gonzalez, M. A. (2003). Continent Divides in North Dakota and North America. Department of Mineral Resources, North Dakota. https://www.dmr.nd.gov/ndgs/documents/newsletter/2003Summer/pdf/Divide.pdf

Lienhard, J. H. (n.d.). No. 2634: Triple divides. University of Houston. https://uh.edu/engines/epi2634.htm

Sanderson, Dale. Parting of the Waters. Accessed 17 March 2020. Retrieved from https://www.usends.com/parting-of-the-waters.html

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