Yellowstone’s Isa Lake is a fairly unremarkable pond except for one unique quality: it’s the only lake in the world known to drain into both the Atlantic and Pacific Oceans.
Located in the Yellowstone National Park between the Old Faithful and West Thumb geyser basins, Isa Lake sits directly on the Continental Divide of North America. This crest of mountains runs vertically down through North America, separating the major watersheds flowing to different oceans.
As a result of its unique location, the east side of Isa Lake drains into the Lewis River, a tributary of the Columbia River, and eventually into the Pacific Ocean. Meanwhile, the west side of the lake drains into the Firehole River, a tributary of the Madison River, and ultimately to the Gulf of Mexico, which is linked to the Atlantic by the Straits of Florida.
This direction of drainage is the opposite of what might be expected; its eastward outlet goes to the Pacific in the west, and its westward outlet heads towards the Atlantic in the southeast. This counterintuitive route of the rivers is another quirk of Yellowstone’s unique, winding topography.
Some sources suggest Isa Lake only drains out of both outlets during times of high water, namely in periods of strong snow melt after winters with heavy snowfall. Nevertheless, it’s still a fairly remarkable trait.
The Great Continental Divide in North America in red, as well as the continent’s other drainage divides.
A similar phenomenon also occurs at the significantly larger Lake Ladoga near St Petersberg in northwestern Russia, close to the Finnish border. Much of the lake drains into the Gulf of Finland via the Neva River, which eventually leads to the Baltic Sea. However, the lake also has tributaries that are hooked up to the Volga River system, which connects to the Caspian Sea.
Speaking of strange bodies of water, we should mention the Nerodime River in southern Kosovo. On the outskirts of the city of Ferizaj, the river forks into two paths, a feature known as a river bifurcation. The left branch flows into the Black Sea, while the right branch flows into the Aegean Sea, making it the only example of a European river flowing into two seas.
Source Link: Isa Lake: The Only Lake That Flows Into Both The Atlantic And Pacific Ocean
