What Is the Theory of Plate Tectonics?

By Staff WriterLast Updated Mar 27, 2020 4:43:22 PM ET

The theory of plate tectonics states that the Earth's surface, the upper mantle and crust, was once made up of enormous rock plates that broke into smaller pieces approximately 300 million years ago. These smaller, broken plates form a more fluid rock surface in the mantle. Over time, the plates move and morph into natural land boundaries. This explains natural land phenomena, such as earthquakes and tsunamis.

In 1912, meteorologist Alfred Wegener proposed the first plate tectonics theory: all of the continents, at one time, were connected and formed a single super-continent called Pangaea. This explains why the coastlines of the continents appear to fit together like pieces of a puzzle.

During hundreds of millions of years, the plates have moved and changed position. Sometimes they move together, sometimes they separate and move apart and sometimes they move past each other. When the plates move past each other, they sometimes touch and make one plate rise up as the other slides down. That up-down movement causes an earthquake, which results in a land fault or crack. If the movement happens in a large body of water, it can create giant water waves called tsunamis. The major plates are known as North America, South America, Eurasia, Africa, Indo-Australian, Pacific and Antarctica.