What is an earthquake?

The surface of the Earth is made up of huge chunks of rock called tectonic plates, which move around but only about as quickly as your fingernails grow. As they move, they push against each other and can get stuck. As they keep trying to slide, they push harder and harder and eventually slip. When this happens, we feel the ground shake - an earthquake. Earthquakes usually happen near the areas where one plate meets another (called fault lines) such as The Ring of Fire.

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How are earthquakes measured?

A machine called a seismometer measures how much the ground is moving and draws a graph called a seismograph. The bigger the wiggles on the graph, the more the ground is moving and the worse the earthquake.

When we measure a distance we use metres or centimetres. When we measure earthquakes, we use a number between 0 and 10 on the Richter Scale.

Earthquakes under water

When there is an earthquake under water, the ground moving can make a wave in the sea. This is called a tsunami.