Isa Lake in Yellowstone has the unique characteristic of draining into both the Atlantic and Pacific Oceans.
Located in Yellowstone National Park between the Old Faithful geyser and West Thumb, Isa Lake sits directly on the North American Divide, also known as the Rocky Mountains. This mountain range stretches across North America, separating the flow of river systems to the east and west, leading into different oceans, according to IFL Science.
Isa Lake in Yellowstone National Park. (Photo: Wikimedia).
The unique location results in the eastern part of Isa Lake draining 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 Florida Strait.
Isa Lake is situated at an elevation of 2,518 meters. In spring, when it overflows due to melting snow, the lake’s water flows in two directions. Because Isa Lake is located in a basin, it only drains into the ocean when the water level is sufficiently high. In many recent winters, the snowfall in Yellowstone has not been thick enough to fill the lake. This has turned Isa into a closed lake, with water flowing in but not flowing out. Most of the year, the water in Isa Lake does not drain into either ocean but evaporates under the heat.
A similar phenomenon occurs at the much larger Lake Ladoga located near St. Petersburg in northwestern Russia, close to the Finnish border. Most of the lake drains into the Gulf of Finland via the Neva River, which ultimately flows into the Baltic Sea. However, the lake is also connected to tributaries in 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 two-headed river. The left branch drains 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.
