Welcome to the Denmark Strait cataract, between Greenland and Iceland. It is where we find the world's biggest waterfall, but it's underwater. It's roughly 300 miles across and falls 11,500 feet, sending a massive amount of water into the Atlantic Ocean every second - like, one and a half Great Pyramids of Giza worth of water. Per NOAA, "Cold water is denser than warm water, and in the Denmark Strait, southward flowing frigid water from the Nordic Seas meets warmer water from the Irminger Sea. The cold, dense water quickly sinks below the warmer water and flows over a huge drop in the ocean floor, creating a downward flow." This is a vitally important part of the system of ocean currents known as the Atlantic Meridional Overturning Circulation, or "a large global conveyor belt," which circulates water from north to south and back in a long cycle. It brings cooler waters and climactic stabilization as well as oxygen, nutrients, and organic matter cruci...