Earthquakes and Tectonic Plates

The outer layer of the Earth is not one solid shell — it is broken into about a dozen huge pieces called tectonic plates. These plates float very slowly on hot, soft rock beneath them, moving just a few centimetres each year. Although it feels as though the ground beneath your feet is perfectly still, you are in fact riding on a gigantic, slow-moving raft of rock.

To picture how the Earth is built, imagine a peach. The thin skin is like the crust we live on. The thick, juicy part is the mantle, made of hot rock that can flow very slowly like thick treacle. Right in the middle is the stone, which is like the Earth's super-hot core. The tectonic plates are pieces of that thin crust, floating on the mantle below.

Where plates meet, extraordinary things happen. When two plates push together, mountains form. When they pull apart, hot rock rises and volcanoes can erupt. When they slide past each other, the rough edges catch and then suddenly slip, and the ground shakes — that is an earthquake.

The point underground where an earthquake starts is called the focus. Directly above it on the surface is the epicentre — the place that usually feels the shaking most strongly. Scientists measure the strength of earthquakes using instruments called seismometers, which record the trembling and turn it into a number on a scale. The bigger the number, the more powerful the earthquake.

In countries that have many earthquakes, people prepare carefully to stay safe. Engineers design buildings that can sway gently instead of snapping, and children practise 'drop, cover, and hold on' drills at school, ducking under sturdy tables. Being ready means far fewer people are hurt when the ground does shake.