What Is Unique About Wyoming's Isa Lake?

Isa Lake is often covered with yellow pond lilies during summer.

A Continental Divide is like a roof of a house. As the rain falls, the roof either diverts the water to the front yard or backyard. Geologically, the phenomenon is true for the continental divide. But, instead of the front and backyard, the rain falling on the divide ends up either in the Pacific or Atlantic Oceans. However, there is an exception to some of the waters that end up in the two oceans. Interestingly, the waters of Isa Lake, situated in Yellowstone National Park, flows into both the Pacific and Atlantic Oceans. The Two-Ocean Lake also drains backward or in the opposite direction.

Isa Lake

Isa Lake is a natural lake situated in Yellowstone National Park in Wyoming, the US. The continental divide is straddled by the lake at Craig Pass at an elevation of 8,262 feet. Isa Lake was discovered by Hiram Chittenden in 1891 as he was exploring a shorter route that connects Old Faithful to the West Thumb. The lake was named after Miss Isabel Jelke of Cincinnati. However, very little is known about Jelke or her relationship to the lake and why the lake was named so. Isa Lake is one of the two lakes and the only known natural lake in the world that drains into two oceans. The other lake that drains into two oceans is Gatuna Lake which is an artificial lake. Also, Isa Lake is also interesting in that it drains into the two oceans backward.

Geography of Isa Lake

Isa Lake is located approximately halfway between Old Faithful and West Thumb geyser basin on the Grand Loop Road in Yellowstone National Park. The lake is more of a pond than a lake and sits within the Craig Pass at an elevation of 8,262 feet. It freezes over winter and is often covered with yellow pond lilies during summer. Isa Lake has two outlets and no inlet. When the mountain snow melts, the runoff swells the bank of the river. The outlet on the western end of the lake flows into the Firehole River which flows into Mississippi and Missouri River and eventually into the Gulf of Mexico and Atlantic Ocean. The outlet on the eastern end of the lake leads to the nearby Shoshone Lake which drains into the Pacific Ocean via Lewis, Columbia, and Snake Rivers. Thus, Isa Lake is the only known natural lake worldwide that drains to two oceans. Notably, the Atlantic Ocean is on the east of Isa Lake while the Pacific is on the west. It is expected that the outlet on the east leads to the Atlantic and the one on the west leads to the Pacific Ocean. However, that is not the case as the outflow is counterintuitive, another feature that makes the lake interesting.

Visiting The Lake

Isa Lake is easily accessible since it is located near the road that links the Old Faithful to the West Thumb geyser basin. The road at Craig Pass is marked as the continental divide. There is a sufficient parking area near Isa Lake Bridge. Apart from the fascinating water that drains into both the Pacific and Atlantic Oceans, Isa Lake also has lots of beautiful lily pads floating on the water.


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