Yellowstone National Park is famous for many things.

For one, its animals. Yellowstone has a huge diversity in the animal species roaming around its impressive expanse, with moose, coyotes, cougars, grizzly bears, bison, wolverine, and lynx among some of the many mammals alone that call this place home.

At over 3,500 miles, Yellowstone is one of the biggest national parks in the US, spanning three states. While most of the park is in Wyoming, it also extends out into Idaho and Montana too.

Yellowstone is packed with geothermal activity. Not only the site of a huge dormant volcano, the national park is home to more than half of the world’s active geysers; its most famous, Old Faithful, erupts regularly, much to the delight of visitors.

But the most unusual thing about Yellowstone National Park?

It is home to one of the most unique lakes in the world.

And nope. It’s not Yellowstone Lake; although this is the highest mountain lake of such a huge size in all of the US. It’s not the park’s second biggest lake, Shoshone Lake, either.

This lake is Isa Lake, a relatively small lake that sits at an elevation of 2,518 meters.

Why is Isa Lake so special?

Well it just happens to be the place where the Atlantic and Pacific Oceans meet. This unassuming lake is the only one in the world that drains into both of these mighty oceans.

And this is because Isa Lake, located at Craig Pass, straddles the continental divide. These mountains are known as the continental divide because they divide the continent hydrologically. That is, the water that runs down the mountains to the east eventually drains into the Atlantic Ocean. The water that runs down to the west drains into the Pacific.

The spectacular location of Isa Lake means that to the east it drains into the Lewis River, and to the west it drains into the Firehole River. Both of these rivers are tributaries of other, larger rivers (the Columbia River and the Madison River, respectively). After winding their way through the country, the water from these rivers drains out to the ocean on opposite sides of the continent: the water that flowed east heads into the Pacific and the water to the west into the Atlantic.

But wait! Isn’t that the wrong way round? Surely the water to the east would drain into the Atlantic and the west would drain into the Pacific?

Well, no. Because of the windy nature of Yellowstone’s mountain ranges, water draining to the east actually winds round and ends up to the west, while the water draining to the west loops round to flow southeast.

This is just one of the many wonders of Yellowstone’s unique geography.

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