Plate Tectonics Explained: Why Earthquakes and Volcanoes Happen
The Earth’s outer layer is not one solid shell. It is broken into large pieces called tectonic plates that float on the hotter, softer rock beneath and move a few centimetres each year. Where they meet, dramatic things happen.
The three types of boundary
Almost all earthquakes and volcanoes happen at plate boundaries. There are three kinds.
- •Convergent: plates push together — forming mountains or deep ocean trenches and volcanoes.
- •Divergent: plates pull apart — new crust forms, as at mid-ocean ridges.
- •Transform: plates slide past each other — causing earthquakes, like the San Andreas Fault.
What drives the movement
Heat from deep inside the Earth creates slow-moving currents in the mantle, called convection currents. These drag the plates along, a bit like objects floating on a very slow, very thick boiling liquid.
Why it matters
Plate tectonics explains earthquakes, volcanoes, mountain ranges, and even why the continents fit together like puzzle pieces — evidence that they were once joined in a supercontinent called Pangaea.
Frequently asked questions
What are tectonic plates?
Large pieces of the Earth’s outer shell that float on the mantle and slowly move.
Why do earthquakes happen at boundaries?
Stress builds as plates push, pull or grind past each other, then releases suddenly as an earthquake.