Earthquakes: Causes, Effects & Responses

Earthquakes are one of the most destructive natural hazards on Earth. This lesson covers how and why earthquakes happen, the effects they have on people and the environment, and how communities respond. You will study contrasting case studies from a higher-income country (HIC) and a lower-income country (LIC) — a key requirement of the AQA specification.

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How Earthquakes Occur

An earthquake is a sudden and violent shaking of the ground caused by the release of energy stored in rocks along a fault line or plate boundary.

The Process

1. Tectonic plates are constantly moving, but friction at plate boundaries causes them to lock together.
2. Stress (pressure) builds up over time as the plates continue to be pushed by convection currents.
3. When the stress exceeds the strength of the rocks, they fracture and the plates suddenly move.
4. Energy is released as seismic waves that radiate outward from the point of fracture.

Key Terms