Features & Impacts of Earthquakes & Volcanoes (Cambridge (CIE) IGCSE Environmental Management): Revision Note

Features of earthquakes

• An earthquake is the sudden, violent shaking of the ground

• They are the result of pressure building when tectonic plates move

Release of energy

• Stored elastic energy is released as seismic waves, causing shaking.

Focus

• The point inside the Earth where the earthquake starts

Epicentre

• The point directly above the focus on the surface

• Usually experiences the strongest shaking

Magnitude (Moment Magnitude Scale)

• Measures the energy released (strength/power) of earthquakes

• Logarithmic: each whole-number increase is ~32× more energy

• More accurate for large earthquakes than the older Richter scale

• The damage caused by earthquakes is measured on the Mercalli Scale

Features of volcanic eruptions

• Volcanic eruptions vary from gentle lava flows to catastrophic explosions

• Key features include:

• Magma rising to the surface

  • Magma rises through cracks due to buoyancy and gas pressure

  • When magma reaches the surface, it becomes lava and forms new crust and volcanic landforms

• Ash

  • Tiny fragments of rock and volcanic glass

  • Can travel globally in the upper atmosphere

  • Heavy ashfall collapses roofs, suffocates vegetation, and disrupts transport

• Gases (H₂O, CO₂, SO₂)

  • Water vapour is the most common volcanic gas

  • CO₂ can accumulate in low areas and cause suffocation

  • SO₂ forms volcanic smog and contributes to acid rain and atmospheric cooling

• Acid rain

  • Forms when SO₂ reacts with water in the atmosphere

  • Damages vegetation, acidifies soils and water bodies, and corrodes stone

• Volcanic bombs

  • Large, molten or semi-molten rocks ejected during explosive eruptions

  • Cool as they travel, landing as solid rock — dangerous at close range

• Pyroclastic flows

  • Fast-moving clouds of hot gas, ash and rock fragments

  • Can exceed 400°C and travel at >100 km/h

  • Extremely destructive and often fatal

  • Responsible for many historical volcanic disasters (e.g. Mont Pelée 1902)

Measuring eruption magnitude

• The magnitude of a volcanic eruption is measured on the Volcanic Explosivity Index (VEI)

Opportunities provided by volcanoes

• Although volcanoes pose serious hazards, they also create valuable opportunities that attract people to volcanic regions

• These benefits often outweigh the risks, especially in countries where the land and resources around volcanoes support livelihoods and economic development

Fertile soils

• Volcanic activity produces ash, lava and rock fragments that eventually break down into highly fertile soils

• Why they are fertile:

  • Volcanic materials weather into soils rich in minerals, especially potassium, phosphorus, magnesium and iron

  • These nutrients make soils excellent for crop growth

• Examples:

  • The slopes of Mount Etna (Italy) are famous for citrus orchards and vineyards

  • Java (Indonesia) supports rice farming on volcanic soils that feed millions

• Why people live there:

  • Reliable, productive farmland that increases food security and income

Extraction of minerals

• Volcanoes bring valuable minerals and metals close to the Earth’s surface, making them easier to mine

• Key volcanic minerals include:

  • Copper

  • Gold

  • Silver

  • Lead and zinc

  • Sulphur (from volcanic gases and fumaroles)

• How they form:

  • Hot volcanic fluids deposit minerals in cracks and fissures

  • Repeated eruptions concentrate valuable ore bodies

• Benefits:

  • Mining creates jobs and export income

  • Supports local industry and national economic growth

• Examples:

  • Copper mining in the Andes (Chile, Peru)

  • Sulphur mining in Indonesia from active volcanic vents

Building materials

• Volcanoes produce materials that are widely used in construction and industry

• Common volcanic building materials:

  • Basalt: hard rock used for road building and building blocks

  • Pumice: lightweight and porous; used in concrete, abrasives, and horticulture

  • Scoria: used for drainage, landscaping, and lightweight construction

• Why they’re useful:

  • Durable, abundant, and easy to quarry near volcanic regions

• Example:

  • Volcanic stone from Iceland and Hawaii is used in construction and coastal engineering

Geothermal power

• Volcanoes provide a reliable and renewable source of geothermal energy

• How it works:

  1. Heat from magma warms underground water

  2. Hot water becomes steam

  3. Steam is extracted through wells

  4. It drives turbines that generate electricity

• Benefits:

  • Clean and sustainable energy source

  • Reduces reliance on fossil fuels

  • Provides heat for homes, greenhouses, and industries

• Examples:

  • Iceland generates about 25–30% of its electricity from geothermal power

  • New Zealand uses geothermal heat for spas, heating and electricity

Tourism

• Volcanic landscapes are major attractions for domestic and international visitors

• Tourism activities include:

  • Hiking volcanic cones (e.g., Mount Fuji, Japan)

  • Visiting hot springs and geysers (e.g., Yellowstone, USA)

  • Viewing lava flows (e.g., Hawai‘i Volcanoes National Park)

  • Exploring volcanic beaches, crater lakes and lava tubes

• Benefits:

  • Generates employment (guides, hotels, restaurants)

  • Boosts local and national economies

  • Encourages conservation of volcanic landscapes

• Why tourism thrives:

  • Volcanoes offer dramatic scenery and unique natural features

  • Cultural significance adds value (e.g., rituals and traditions around volcanoes)

Impacts of tectonic events

• Tectonic hazards affect societies at every level, such as infrastructure, health, economy, and ecosystems

• Impacts vary depending on:

  • Magnitude

  • Distance from the epicentre/volcano

  • Population density

  • Building quality

  • Preparedness

• The impacts of earthquakes and volcanic eruptions can be categorised into:

  • Primary hazards: these are a direct result of the earthquake or eruption

  • Secondary hazards: these occur as a result of the primary effects

• Damage to buildings and infrastructure

  • Earthquake shaking collapses homes, bridges, and pipelines

  • Lava and pyroclastic flows destroy everything in their path

  • Roads become impassable, slowing rescue and recovery

  • This leads to people being homeless for months and even years after the event

  • The more buildings that are destroyed or damaged, the higher the costs of rebuilding

• Loss of crops, livestock and habitats

  • Ash covers farmland; lava buries fields, causing the death of crops

  • Earthquakes can destroy irrigation and greenhouses

  • Wildlife habitats burn or become uninhabitable

  • This leads to food shortages and affects farmers' income

• Evacuation of people and livestock

  • Volcanic warnings often lead to mass evacuations

  • Tsunami threats require rapid coastal evacuation

  • Evacuation disrupts livelihoods and may become long-term

• Fire

  • Ruptured gas lines ignite after earthquakes

  • Lava ignites forests and settlements

  • Fires spread quickly when emergency services are limited

• Tsunamis

  • Triggered by undersea earthquakes, volcanic eruptions or landslides

  • Flood coastlines, destroy infrastructure and cause high death tolls

• Landslides

  • Shaking destabilises slopes

  • Volcanoes produce lahars (mudflows) when ash mixes with water

  • Landslides bury communities and block rivers

• Contamination of drinking water

  • Ash and debris pollute reservoirs

  • Broken sewage pipes contaminate supply lines

  • CO₂ emissions from volcanoes may reach groundwater

    • Volcanic plume emissions dissolve in the atmospheric water, which infiltrates the surface after precipitation and percolates downwards

    • When magma rises, gases like CO₂ and sulphur are released into fissures, faults, and porous surfaces

    • These gases dissolve in underground water sources, lowering the pH and increasing acidity

• Water-related disease

  • Flooding and infrastructure collapse cause outbreaks

  • Examples: cholera, dysentery, gastroenteritis

  • Poor sanitation in evacuation shelters increases risk

• Financial losses

  • Rebuilding is expensive

  • Tourism declines after major events

  • Agriculture, business and industry all face disruption

  • It is dangerous for jet planes to fly through ash clouds due to possible engine failure, so flights are cancelled

• Human health

  • Injuries from collapsing structures, burns, and inhalation of ash

  • Long-term respiratory issues from ash and toxic gases

  • Mental health effects (trauma, anxiety, displacement)