Earthquakes & Volcanoes (Cambridge (CIE) IGCSE Geography)

The Ring of Fire is the area around the rim of the Pacific Ocean where approximately 90% of earthquakes and 75% of active volcanoes occur.

False.

Earthquakes occur at all types of plate boundaries.

A hotspot is a plume/column of magma which escapes through the Earth's crust away from plate boundaries.

Approximately 75% of active volcanoes are located around the Pacific Ring of Fire.

True.

Most volcanoes occur at divergent and convergent plate boundaries.

The general pattern of earthquake distribution is that they mostly occur along plate boundaries, with the majority along the Pacific Ring of Fire.

A plate boundary is where two tectonic plates meet.

Most volcanoes occur at divergent and convergent plate boundaries, with some occurring at hotspots away from boundaries.

False.

Volcanoes can occur at hotspots away from plate boundaries.

The four main layers of the Earth are the:

• Crust.

• Mantle.

• Outer core.

• Inner core.

Continental crust is thick (25-90 km), old, and less dense than oceanic crust.

Tectonic plates move in part because of convection currents in the mantle.

The four main types of plate boundaries are divergent (constructive), convergent (destructive), collision, and transform (conservative).

False.

Volcanoes do not occur at collision boundaries or transform (conservative) boundaries.

At a divergent plate boundary, the plates are moving apart, allowing magma to rise and form new crust

Subduction is the process where one tectonic plate moves under another at a convergent plate boundary.

At a hot spot, a plume of magma rises to the surface through cracks in the crust as the tectonic plate moves over it.

False.

Earthquakes can occur anywhere but mostly occur at or near plate boundaries.

Convergent (destructive), collision, and transform (conservative) plate boundaries typically produce stronger earthquakes.

The difference is that primary hazards are direct results of an earthquake or eruption, while secondary hazards occur as a result of the primary effects.

Liquefaction is the process where soil behaves like a liquid due to stress such as earthquake shaking.

False.

Building construction and design significantly affect the impact of earthquakes.

Factors affecting volcanic eruption impacts include:

• Proximity of population.

• Planning and preparation.

• Magnitude of the eruption.

• Type of volcano.

• Amount of ash ejected.

A pyroclastic flow is a fast-moving current of hot gas and volcanic matter that flows along the ground during some volcanic eruptions.

Common long-term impacts of volcanoes and earthquakes include:

• Collapse or destruction of buildings.

• Transport network damage.

• Loss of jobs and businesses.

• Loss of crops.

• Power and water supply damaged.

• Damage to the environment.

False.

Ash from volcanic eruptions can affect areas hundreds of kilometres away and impact global climate.

Earthquakes and volcanic eruptions can lead to closure of airports and cancellation of flights, particularly due to ash clouds from eruptions.

Surface rupture is the breaking and displacement of the ground surface along a fault during an earthquake.

The closer somewhere is to the epicentre the stronger the shock waves will be which can mean there will be more impact.

It is estimated that 600 million people will live in tectonically active areas by 2025.

Geothermal energy is heat from the Earth that can be used to generate power, often in volcanic areas where magma is closer to the surface.

False.

Living near volcanoes presents both hazards and opportunities, such as fertile soil and tourism.

Volcanic ash creates fertile soils rich in minerals, leading to high crop yields.

Resilience is the ability of communities in earthquake-prone areas to prepare for, respond to, and recover from seismic events.

Volcanic areas provide economic opportunities in several ways:

• Jobs in tourism.

• High yields of crops.

• Geothermal energy.

• Minerals and precious stones.

False.

Some people have little choice but to live in earthquake zones due to limited financial resources, despite the risks.

Living in earthquake zones can lead to research and innovation in earthquake prediction, early warning systems, and building strength.

Short-term responses happen immediately after an event and include aid and disaster relief, while long-term responses aim to reduce the impact of future events and include risk assessments and hazard mapping.

A tiltmeter is a device used to monitor ground slope changes as part of earthquake prediction efforts.

Cross-bracing is a technique used in earthquake-resistant building design where diagonal supports are added to steel frames to increase stability.

False.

Accurate prediction of earthquakes is not currently possible, but monitoring is ongoing.

Earthquake drills help people prepare for what to do in an earthquake to protect themselves.

Remote sensing, such as satellite imagery, provides data about changes in ground movement to help monitor volcanic and seismic activity.

False.

Land use planning is crucial in reducing hazards by ensuring valuable services are not built in high-risk areas.

Automatic cut-offs for gas and electricity help prevent fires and explosions that could occur due to damaged utility lines during an earthquake.

Seismic retrofitting is the modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquakes.

There were several long-term responses to the Nepal earthquake including:

• Landslides being cleared and roads repaired to restore access to remote rural communities.

• Schools were rebuilt.

• Earthquake drills were introduced.

• Stricter building codes with more enforcement.

• $200 million was provided by the Asian Development Bank for rebuilding.

• A new government task force was set up to plan for future earthquake events. 

There were approximately 9 000 people killed in the Nepal earthquake.

True.

Over 6 000 people were evacuated as a result of the Cumbre Viejo volcano eruption.