Science
What is Earthquake?
An earthquake is a sudden shaking of the ground caused by the movement of rock deep within the Earth. Most happen when the giant plates that make up Earth's surface slip past each other along a fault, releasing built-up energy as seismic waves.
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Watch a 2-minute lesson with voice + animation that explains earthquake.
Key things to understand
- 1Earth's outer shell is broken into tectonic plates that slowly move; where they meet, stress builds up over years.
- 2When the stuck rock suddenly slips, the stored energy is released as seismic waves that shake the ground.
- 3The point underground where it starts is the focus; the spot directly above it on the surface is the epicenter.
- 4Strength is reported as a magnitude — each step up the scale is about 32× more energy released.
- 5Most earthquakes happen along plate boundaries, like the Pacific 'Ring of Fire'.
Frequently asked questions
- What causes earthquakes?
- Mostly the movement of tectonic plates. Stress builds where plates grind together, and when the rock suddenly slips along a fault, the released energy shakes the ground. Volcanic activity can trigger them too.
- How are earthquakes measured?
- By instruments called seismographs that record the seismic waves. The size is reported as a magnitude (e.g. 6.0); the shaking actually felt at a place is its intensity.
- Can earthquakes be predicted?
- Not precisely. Scientists can map high-risk zones and estimate probabilities, but no one can yet reliably predict the exact time and place of a specific earthquake.