About 270 million years ago, the land that was to become the seven continents had formed Pangaea, one huge supercontinent.
All around it flowed a superocean, called Panthalassa, or universal sea. Then, some 210 million years ago, Pangaea began to split up, creating a north-south rift that filled with water from Panthalassa.
This waterway became the Atlantic Ocean. Land masses began floating to their current positions. More than 100 million years later, Pangaea had broken apart and between the moving continents, the Indian and Arctic oceans formed.
By the time the continents had found their current locations, the Pacific and Antarctic oceans existed. At the same time the Atlantic Ocean was forming, water began to creep inland, creating seas and lakes.
In 1960, researchers took the deepest measurement of the ocean in history: just over 36,000 feet (11,000 meters) at the Marianas Trench in the Pacific Ocean.