Some of the most stunning and spectacular sites on the planet are waterfalls. Not only are they beautiful, but these natural water breaks can have cultural significance, help shape landscapes, create microclimates, and even be used as a source of hydroelectricity.
The tallest waterfalls on the planet can reach heights of over 1,000 feet, with millions of gallons of water spilling over them. And while the tallest waterfall on land is Angel Falls in Venezuela, which stands at 3,212 feet tall, the tallest waterfall in the world is actually underwater.
The Denmark Strait Cataract
An underwater waterfall seems counterintuitive; however, experts consider the Denmark Strait cataract as the world’s tallest. The Denmark Strait cataract is an overflow that channels water through the Denmark Strait — which is situated between Iceland and Greenland. The cataract is a tall rock outcropping jutting towards the surface from the sea floor, and over the cataract’s edge, there is an 11,500-foot drop.
The 123 million cubic feet of water passes over the cataract per second, which can put Angel Falls to shame. The water that flows past the Denmark Strait cataract is about 1,300 feet deep. However, as that water passes the cataract, only about 660 feet of that initial 1,300 falls towards the sea floor. The rest of the water flows over it to mix with warmer water.
But how does water fall underwater? It all comes down to salinity and water temperature.
Read More: Why Is the Ocean Salty?
A Waterfall Underwater
It’s common knowledge that heat rises. The same goes for warmer waters. Cooler waters from the Nordic Seas flow through the Denmark Strait and out towards the Atlantic Ocean. Before reaching the strait, some of the polar waters freeze, causing more salt to mix into the unfrozen water. This colder, saltier ocean water is denser and flows closer to the sea floor.
As this water approaches the cataract, the warmer waters are pushed toward the surface, and the colder waters sink. The cold water then pours over the cataract towards the seabed. The remaining cold water on the seafloor then creates an icy current that carries water out to the Irminger Sea – in the Atlantic Ocean.
You would think that with the amount of water that goes over the cataract, the current would be swift. However, because the water temperature is so cold, the water actually falls rather slowly — at about 1.6 feet per second.
Importance of the Denmark Strait Cataract
An underwater waterfall may be a wonder to behold, but it is also a crucial part of our interconnected oceans. Waters from the Denmark Strait help feed into the Atlantic Meridional Overturning Circulation (AMOC), a crucial network of ocean currents that move cold waters south and warm waters north. This current system helps move vital nutrients throughout the Atlantic Ocean and helps ensure marine life can thrive.
However, the risk of climate change could disrupt the cold water flows through the Denmark Strait. As ocean waters warm and ice caps melt, the salinity levels in polar waters are decreasing, meaning less water could flow over the cataract.
You may not be able to see the world’s largest waterfall from a spectacular viewing platform or from a boat while wearing a rain poncho; in fact, without modern mapping and monitoring technology, it would almost look like nothing is going on at all. But the waters from the Denmark Strait cataract are still flowing, and for the sake of our oceans, let’s hope they continue to do so.
Read More: Why It’s Alarming That Deep-Sea Currents are Beginning to Slow
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A graduate of UW-Whitewater, Monica Cull wrote for several organizations, including one that focused on bees and the natural world, before coming to Discover Magazine. Her current work also appears on her travel blog and Common State Magazine. Her love of science came from watching PBS shows as a kid with her mom and spending too much time binging Doctor Who.
