The only lake that flows into both the Atlantic and Pacific Oceans

Lake Isa in Yellowstone has the unique feature of flowing into both the Atlantic and Pacific Oceans.

Located in Yellowstone National Park between Old Faithful and the West Thumb geysers, Lake Isa sits directly on the North American Divide, or Rocky Mountains. This mountain range runs across North America, separating the river system's flow east and west, emptying into different oceans, according to IFL Science .

Lake Isa in Yellowstone National Park. (Photo: Wikimedia).

As a result of its unique location, the eastern part of Lake Isa drains into the Lewis River, a tributary of the Columbia River, which flows into the Pacific Ocean. Meanwhile, the western part of the lake drains into the Firehole River, a tributary of the Madison River, which flows into the Gulf of Mexico, connecting to the Atlantic Ocean via the Straits of Florida.

Lake Isa sits on a mountain pass at an elevation of 8,000 feet (2,518 m). In the spring, when the snowmelt overflows, the lake flows in two directions. Because Lake Isa is in a basin, it only flows into the ocean when the water level is high enough. In recent winters, the snowpack in Yellowstone has not been deep enough to fill the lake. That makes Lake Isa a closed lake, with water flowing in but not out. For most of the year, the water in Lake Isa does not flow into the two oceans but evaporates in the hot sun.

A similar phenomenon occurs at the much larger Lake Ladoga, located near St Petersberg in northwestern Russia, close to the Finnish border. Most of the lake drains into the Gulf of Finland via the Neva River, eventually reaching the Baltic Sea. However, the lake is also connected to a tributary of the Volga river system, which flows into the Caspian Sea.

Another example is the Nerodime River in southern Kosovo . Located on the outskirts of the city of Ferizaj, the river splits into two branches , known as the fork. The left branch flows into the Black Sea while the right branch flows into the Aegean Sea, making it the only river in Europe that flows into two seas.