How does an earthquake cause a tsunami?

Here is my final version of how does an earthquake cause a tsunami?

A tsunami can happen when one tectonic plate is forced underneath another on the seabed. This movement is slow and gradual and can go on for centuries. Eventually the strain on the upper plate becomes too much and it lurches violently upwards causing an earthquake. The vast amount of water pushed upwards by the earthquake can create a tsunami.

Tectonic plates make up the earth’s surface. They rest on a vast layer of hot rock called the mantle. These plates are moving slowly at all times. Where the edges meet they either slide past each other, scrape together or crash head on. The area where the plates meet is called a fault line.

Earthquakes are measured on the Richter Scale. The higher the reading on the scale, the larger the earthquake and larger the tsunami. The same is when it is a low reading on the Richter Scale.

Seismic activity is the most common cause of tsunamis. Over the past two millenniums earthquakes have produced 82.3% of all tsunamis.