Energy from the sun causes currents to flow. Water lying near the equator is heated more than water at middle latitudes, causing a surface flow towards the poles. When two currents meet, the colder water sinks, pushing warmer water up to the surface.

One of the strongest known currents is the Gold Stream, which runs along the eastern coat of the USA. It is up to 37 miles wide and 2600 feet deep.

The Humboldt Current on the west coast of South America, brings cold water to the surface. At the same time, it brings minerals and other nutrients, which feeds huge schools of fish.

The Kuroshio Current, off the shores of Japan, is the largest current. It can travel 40-120 km per day at speeds of 1.5-4.5 kph. The Gulf Stream, in the Atlantic Ocean, is close to this speed. At a speed of more than 95 km per day, the Gulf Stream moves 100 times as much water as all the rivers on earth and flows at a rate which is 300 times faster than the Amazon, which is the world’s largest river.