Plate Tectonic Basics

Science

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What Is Plate Tectonics

The theory of plate tectonics explains how Earth’s outer layer, called the lithosphere, is broken into large pieces called tectonic plates. These plates fit together like a giant puzzle and move slowly over the softer, hotter layer beneath them.

Tectonic plates move only a few centimetres each year. Their movement is caused by heat from inside Earth. This heat creates slow movements in the mantle, which help push and pull the plates.

There are three main types of plate boundaries. At a convergent boundary, plates move towards each other. At a divergent boundary, plates move apart. At a transform boundary, plates slide past each other.

Earthquakes and Volcanic Activity

Earthquakes happen when stress builds up in rocks along a fault or plate boundary. When the rocks suddenly move, energy is released as vibrations that travel through the ground. Earthquakes are especially common at transform boundaries and convergent boundaries.

Volcanoes often form where tectonic plates move apart or where one plate is forced beneath another. At a divergent boundary, molten rock can rise through gaps between the plates. At a convergent boundary, a sinking plate can melt and produce magma.

Plate tectonics helps explain the locations of many earthquakes, volcanoes and mountain ranges. It also shows that Earth’s surface is constantly changing over very long periods of time.