Earthquakes happen because the Earth's crust is divided into large pieces called tectonic plates that are constantly moving. These plates sometimes get stuck at their edges due to friction, causing stress to build up in the rocks. When the stress becomes too great, the rocks suddenly slip and break along fractures called faults, releasing energy as seismic waves that shake the ground. This sudden movement and release of energy is what causes an earthquake.
How Earthquakes Occur
- The Earth's crust is fractured, and these fractures are called faults.
- Tectonic plates move slowly but can get stuck at fault edges.
- Stress accumulates over time in the rocks near these faults.
- When the stress exceeds the strength of the rocks, they suddenly slip, causing an earthquake.
- The slip releases stored elastic strain energy as seismic waves, which cause the shaking felt during an earthquake.
Key Terms
- Focus (Hypocenter): The underground point where the rock first breaks.
- Epicenter: The location on the Earth's surface directly above the focus.
Additional Causes
While tectonic movement is the main cause of earthquakes, some are triggered by volcanic activity, landslides, or human activities like mining and reservoir filling.
In summary, earthquakes primarily happen because of the sudden release of stress accumulated along faults in the Earth's crust due to tectonic plate movements.
