Causes and Effects of Tectonic Hazards
Learn how plate movement causes earthquakes and volcanoes, then explain the primary and secondary effects of tectonic hazards in GCSE Geography clearly.
Tectonic hazards are caused by the movement of tectonic plates. Their effects can be classified as primary effects, which happen directly, and secondary effects, which result from the primary effects.
Explaining the causes
Tectonic plates are large sections of the Earth’s crust. They move because heat inside the Earth creates convection currents in the mantle.
The type of hazard depends on the plate margin:
- At destructive plate margins, a denser oceanic plate is forced beneath another plate. Friction can cause earthquakes, while rising magma can produce volcanic eruptions.
- At constructive plate margins, plates move apart. Magma rises through the gap, creating volcanoes and shallow earthquakes.
- At conservative plate margins, plates slide past each other. They can become stuck, causing pressure to build. When the plates suddenly move, energy is released as an earthquake. Volcanoes do not normally form here.
Explaining the effects
Primary effects are the direct results of a tectonic hazard. Examples include:
- deaths and injuries
- collapsed buildings and damaged roads
- lava flows, ash clouds and fires
- loss of electricity, water and communications
Secondary effects happen because of the primary effects. For example, damaged roads can delay emergency services, while broken water pipes can cause shortages and disease. Earthquakes may also trigger landslides or tsunamis. Volcanic ash can disrupt flights and damage crops.
Example explanation
“A conservative plate margin can cause an earthquake because the plates become stuck due to friction. Pressure builds until the plates suddenly slip, releasing energy. Buildings may collapse as a primary effect. This can leave people homeless as a secondary effect.”
The severity of the effects depends on factors such as the hazard’s strength, population density, building quality and level of preparation.
Common exam mistake: Do not simply list effects. Clearly link each cause and effect using phrases such as “this causes” or “as a result”.
