Causes of earthquakes and volcanoes

Earthquakes and volcanoes are natural phenomena primarily associated with the movement and interaction of tectonic plates.

Triggers of earthquakes

• Plate boundary activity - Most earthquakes happen at the edges of tectonic plates where stress builds up due to plates moving in opposing directions or at varying speeds. When this stress is released, it results in ground shaking.
• Human-induced causes - Certain human activities can also trigger earthquakes, including:
  • Nuclear testing
  • The immense weight of large dams
  • Drilling for oil or fracking

Triggers of volcanoes

• Plate boundary locations - Volcanoes are commonly found at tectonic plate boundaries where magma can rise to the surface due to plate interactions.
• Hotspot activity - Some volcanoes form away from plate boundaries at hotspots.
• Eruption mechanism - Volcanic eruptions occur when rising magma accumulates in a chamber beneath the surface. As pressure intensifies, it eventually forces an eruption.

Hazards and impacts of earthquakes

Earthquakes pose a range of immediate and subsequent dangers that can devastate communities.

Primary hazards of earthquakes

• Ground shaking - The intense vibration of the Earth's surface during an earthquake can cause structures to collapse.
• Surface faulting - The ground may split or shift along fault lines, directly damaging anything built across these zones.

Secondary hazards of earthquakes

• Ground failure and soil liquefaction - Soft, water-saturated soils can lose strength and behave like a liquid, undermining building foundations.
• Landslides and rockfalls - Slopes destabilised by shaking can collapse, sending rocks and debris downhill.
• Debris flows and mudflows - Heavy rains or melted snow combined with loose material can create destructive flows.
• Tsunamis - Underwater or coastal earthquakes can displace water, generating powerful waves that flood coastal areas.

Impacts of earthquakes on communities

• Human toll - Loss of life
• Economic disruption - Loss of livelihoods
• Structural damage - Total or partial destruction of building structures
• Utility interruptions - Water supplies can be cut off, and sewage systems may break
• Service losses - Loss of public utilities such as electricity or gas
• Environmental hazards - Floods from collapsed dams, release of hazardous materials
• Health concerns - Fires and spread of chronic illness

Hazards and impacts of volcanoes

Volcanic eruptions unleash a variety of threats that can directly harm people and the environment, as well as create longer-term challenges through indirect effects.

Direct hazards of volcanic eruptions

• Pyroclastic flows - Fast-moving currents of hot gas, ash, and rock that can incinerate everything in their path.
• Volcanic bombs - Large projectiles ejected during eruptions.
• Lava flows - Streams of molten rock that can destroy buildings and infrastructure as they advance.
• Ash fallout - Fine particles of volcanic ash that can blanket areas.
• Volcanic gases - Toxic emissions like sulphur dioxide.
• Lahars - Mudflows formed by water mixing with volcanic debris.
• Earthquakes - Ground shaking often accompanies volcanic activity.

Indirect hazards of volcanic eruptions

• Atmospheric ash fallout - Ash can spread over vast distances.
• Landslides - Volcanic slopes can become unstable.
• Tsunamis - Explosive eruptions near water can trigger waves.
• Acid rainfall - Volcanic gases mixing with atmospheric moisture.

Socio-economic impacts of volcanoes

• Settlement destruction - Destruction of settlements
• Loss of life
• Agricultural damage - Loss of farmland and forests
• Infrastructure loss - Destruction of infrastructure – roads, airstrips and port facilities
• Communication breakdowns - Disruption of communications
• Tourism decline - Reduced tourist arrivals
• Investment reduction - Lack of investment
• Job losses - Fewer jobs
• Agricultural earnings drop - Reduced earnings for farmers
• Productivity fall - Decreased productivity
• Population displacement - Out-migration

Opportunities provided by volcanoes

Despite their destructive potential, volcanoes offer unique benefits that can support human life and economic activities.

Benefits arising from volcanic activity

• New land formation - New land and islands for people to live on
• Fertile soils
• Mineral resources - Soils rich in minerals
• Tourism potential - Important as tourist destinations

Strategies for reducing earthquake impacts

Mitigating the effects of earthquakes involves proactive measures to enhance safety and resilience.

Approaches to minimise earthquake damage

• Improved forecasting and warning systems - Better forecasting and warning
• Strategic building locations - Strategic building location
• Enhanced building designs - Enhanced building design
• Emergency procedures

Methods for earthquake prediction and monitoring

Predicting earthquakes remains challenging due to their unpredictable nature, but various techniques are used to monitor potential activity.

Techniques for detecting earthquake risks

• Ground surface changes - Small-scale ground surface changes
• Ground tilt measurements - Ground tilt
• Rock stress variations - Changes in rock stress
• Micro-earthquake activity - Micro-earthquake activity (clusters of small quakes)
• Radon gas concentration changes - Changes in radon gas concentration
• Unusual animal behaviour - Unusual animal behaviour, especially toads