The largest waterfall in the world is not actually on land, but between Greenland and Iceland. This place is called the Danish channel falls by many people. It is formed by the difference in temperature between the very cold arctic waters of the Greenland sea and the slightly warmer waters of the emminger sea.
Molecules in cold water are less active and take up less space than molecules in cold water, so they are packed close together, making cold water denser.
When the waters of the Greenland sea meet those of the emminger sea, it slides down to the bottom. The underwater waterfall is 160 kilometers wide and drops 3,505 meters from the Greenland sea. This is bigger than any waterfall on land.