4. Effects of Earthquakes & Volcanoes

What is the difference between primary and secondary hazards?

• Primary hazards are the direct effects of an earthquake or volcanic eruption.

• Secondary hazards occur as a result of the primary hazards.

State the primary hazards of earthquakes.

• Ground shaking

• Surface rupture

• Liquefaction

• Landslides

State the secondary hazards of earthquakes.

• Tsunamis

• Fires (from ruptured gas and power lines)

State the primary hazards of volcanic eruptions.

• Pyroclastic flows

• Lava flows

• Volcanic bombs

• Ashfall (direct)

State the secondary hazards of volcanic eruptions.

• Lahars (mudflows)

• Earthquakes

• Landslides

• Tsunamis

• Acid rain

• Ash fallout from the atmosphere

Explain one difference between primary and secondary hazards.

• Primary hazards occur immediately from the event, such as ground shaking or lava flow.

• Secondary hazards happen later, for example tsunamis or lahars, caused by the primary effects.

Explain how human factors affect the impacts of earthquakes.

• Building design: poorly built or tall buildings are more likely to collapse.

• Building density: closely packed buildings can damage each other when collapsing.

• Population density: higher population = more injuries and deaths.

• Preparation: earthquake drills and planning reduce impacts.

Explain how physical factors affect earthquake impacts.

• Magnitude: higher magnitude releases more energy → greater damage.

• Geology: soft rocks increase liquefaction; solid rock provides stronger foundations.

• Distance from epicentre: closer areas experience stronger shockwaves.

• Depth: shallow earthquakes cause more damage at the surface.

Explain how human factors affect the impacts of volcanic eruptions.

• Proximity of population: people closer to the volcano are more affected by lava and ash.

• Planning and preparation: evacuation plans and exclusion zones reduce loss of life.

Explain how physical factors affect volcanic impacts.

• Magnitude: larger eruptions cause greater damage.

• Type of volcano: composite volcanoes are more explosive than shield volcanoes.

• Ash in atmosphere: ash can travel hundreds of kilometres and affect climate.

State the main impacts of earthquakes and volcanic eruptions.

1. Loss of life and injury (immediate or from disease later).

2. Collapse of buildings → homelessness.

3. Damage to transport networks, slowing aid.

4. Loss of jobs and businesses, harming the economy.

5. Loss of crops, causing food shortages.

6. Power and water supplies damaged.

7. Environmental damage, including habitat loss.

Explain how earthquakes and volcanoes affect transport and aviation.

• Roads, bridges, and railways can be damaged or destroyed.

• Aid delivery becomes slower and more difficult.

• Airports close because flying through ash clouds can cause engine failure.