Earth's Largest Waterfall Is Hidden Under the Ocean

The biggest waterfall on Earth is one nobody can see. It lies beneath the Denmark Strait, between Iceland and Greenland, where cold water pours down a series of undersea cliffs — a cascade larger and more powerful than any waterfall on land, and invisible without scientific instruments.

How the Denmark Strait cataract forms, where frigid water from the Nordic Seas meets warmer water from the Irminger Sea. Credit: NOAA.

Where it is

At the bottom of the Denmark Strait lies a series of cataracts that begin 2,000 feet below the surface and plunge to a depth of 10,000 feet near the southern tip of Greenland — a drop of nearly two miles. NOAA puts the height of the Denmark Strait cataract at approximately 11,500 feet. The largest waterfall on land is 3,212 feet.

How a waterfall can exist underwater

The secret is that cold water is denser than warm water. In the Denmark Strait, frigid water flowing south from the Nordic Seas meets warmer water from the Irminger Sea. Warmer surface waters flow north, gradually lose heat to the atmosphere and sink; the dense cold water flows south in a deep current along the sea floor, over an undersea ridge in the strait. It sinks quickly beneath the warmer water and spills over the huge drop in the ocean floor.

How much water

The downward flow is estimated at well over 123 million cubic feet per second. Because it all happens beneath the surface, the enormous turbulence of the Denmark Strait goes completely unnoticed from above.

Sources

Based on "Where is Earth's Largest Waterfall?" from NOAA's National Ocean Service, a work of the United States government in the public domain.