A continental divide is a mountainous ridge that separates rivers flowing in different directions. In North America, for example, the Continental Divide of the Americas, which is also called the Great Divide and the Western Divide, creates two different drainage areas. Snow and rain that fall west of the divide eventually reaches rivers that flow toward to the Pacific Ocean. Precipitation that falls east of the divide joins rivers that flow toward the Atlantic and Arctic Oceans and the Gulf of Mexico.

The Great Divide begins in western Alaska and extends south through British Columbia, Canada. It then crests the Rocky Mountains and other ranges in Montana, Wyoming, Colorado, and New Mexico, then continues through Mexico’s Sierra Madre Occidental mountains.

South America’s continental divide lies in the Andes mountains, which separates waters rivers flowing towards the Pacific from those that run toward the Atlantic. It is considered an extension of the Great Divide in North America.

Every continent has at least one continental divide. Antarctica is sometimes considered an exception because it receives little precipitation, and is surrounded by the Southern Ocean. However, the Transantarctic Mountains channel the ice melt from West Antarctica toward the Pacific Ocean and the ice melt from East Antarctica toward the Atlantic and Indian Oceans.

Continents that border more than two bodies of water may have more than one divide. For example, experts believe that North America has several continental divides. The Northern Divide, or Laurentian Divide, separates waters flowing into the Atlantic Ocean from those flowing into the Hudson Bay and the Arctic Ocean. The Eastern Divide separates waters that flow into the Atlantic Ocean from those that empty into the Gulf of Mexico. It is mainly formed by the Appalachian mountains. However, this divide is not recognized by those who contend that the Gulf of Mexico is simply a part of the Atlantic Ocean. The St. Lawrence River Divide separates waters flowing into the the Atlantic Ocean from those that join the Gulf of St. Lawrence. However, as with the Eastern Divide, those who believe that the Gulf of St. Lawrence is part of the Atlantic Ocean do not recognize this feature. The Arctic Divide separates waters that drain to the Arctic Ocean from those that drain to the Hudson Bay.

Image Credit: National Atlas of the United States