The World Ocean, which is all the oceans taken together, covers a total of 139,782,000 square miles (363,433,200 square kilometers)—about 70.8 percent of the Earth's surface. Over 200,000,000 years ago, the World Ocean was one body of water that surrounded one large continent. As time passed, this land mass began to pull apart. As a result, the continents and islands were formed.

The breakup of that one large continent was caused by heat forces welling up from deep within the Earth. As earthquakes split the ocean floor, molten rock from below the Earth's crust flowed into the fracture and became solid. For millions of years this process was repeated until the upper parts of the Earth's crust, on which the continents sit, were pushed even farther apart. About 50,000,000 years ago, the continents took their present shapes and positions.

About 20,000,000 years ago...