What are the effects of earthquakes and volcanoes on people and the environment?

Cambridge iGCSE Geography > The Natural Environment > Earthquakes and Volcanoes > What are the effects of earthquakes and volcanoes on people and the environment?

What are the effects of earthquakes and volcanoes on people and the environment?

The impacts of earthquakes and volcanoes can be categorised into two main groups: primary and secondary effects.

Primary effects are the direct results of an earthquake or volcanic eruption. These might include the collapse of structures owing to seismic shaking or fatalities resulting from pyroclastic flows during a volcanic event.

Secondary effects, on the other hand, are those that follow the primary effects. They occur as a consequence of the initial impacts of the earthquake or volcano. For example, an earthquake might rupture gas lines, leading to subsequent fires, or the destruction of homes in a volcanic eruption might lead to long-term homelessness.

These classifications help understand and analyse the different impact levels of earthquakes and volcanoes on human life, infrastructure, and the environment.

EarthquakeGround Shaking

Surface rupture





Volcanic EruptionPyroclastic flow

Lava flow

Volcanic Bombs

Lahars (mudflow)


Direct ash fall



Acid rain

Ash fallout from the atmosphere

The Effects of Volcanoes and Earthquakes

Volcanic eruptions and earthquakes can affect people and the environment. Effects include:

  1. Loss of life and injury: This can occur immediately due to collapsing buildings or falling ash. In the subsequent days and weeks, the loss of life may continue due to contaminated water or the spread of disease.
  2. Collapse or destruction of buildings: This can leave people homeless for prolonged periods, ranging from months to years after the event.
  3. Impact on transport network: Roads, bridges, and railways may suffer damage or destruction, slowing down aid delivery to affected areas.
  4. Loss of jobs and businesses: The destruction or damage of factories and offices can significantly impact the local economy.
  5. Loss of crops: This leads to food shortages, directly affecting farmers’ income and the overall food supply chain.
  6. Damage to power and water supply: This can disrupt the provision of essential services, particularly affecting the supply of clean water and consequently public health.
  7. Environmental Damage: The eruption may cause the loss of vegetation and habitats, and the presence of ash can even have broader effects on the climate.
  8. Closure of Airports: Flying through ash clouds is perilous for jet planes due to potential engine failure, leading to flight cancellations. This can further hamper relief efforts and disrupt international travel.

Although volcanoes and earthquakes can have similar effects, unlike earthquakes, volcanic eruptions can affect people and places hundreds of miles away. In addition to this, volcanic eruptions can even affect global climate.

Factors Affecting the Impact of Earthquakes

Various factors influence the impact and damage caused by earthquakes. Understanding these can help in risk assessment, planning, and mitigation. Here are the main factors that affect the impact of earthquakes:

  1. Strength and Aftershocks: The magnitude of the earthquake and subsequent aftershocks can determine the damage caused.
  2. Depth of the Earthquake: Deeper earthquakes tend to have their energy absorbed by the crust above, often reducing the surface impact.
  3. Distance from the Epicentre: The further a location is from the epicentre, the weaker the seismic waves and the less damage likely.
  4. Geology of the Area: Areas with looser rocks, such as sedimentary rocks, are more prone to liquefaction, causing structures to sink into the ground.
  5. Quality of Building Materials: Buildings made from poor-quality materials are more likely to collapse.
  6. Building Density: Higher building density increases the risk of swaying buildings affecting others.
  7. Building Height: Taller buildings are more likely to sway and collapse.
  8. Population Density: High-density areas may see more casualties during an earthquake.
  9. Time of Day: The timing of an earthquake can affect its impact; for example, at night, people in older residential areas may be more at risk.
  10. Secondary Hazards: These include tsunamis near coasts, landslides and rockfalls in mountainous regions, and fires due to broken gas pipes in urban areas.
  11. Contamination: Water supplies can become contaminated when mixed with sewage, leading to health issues.

Factors Affecting the Impact of Volcanic Eruptions

As with earthquakes, there are many factors that affect the impact of volcanic eruptions:

  1. Type of Volcanic Eruption: Different eruptions (e.g., explosive vs effusive) can have varying impacts, with explosive eruptions often causing more damage.
  2. Magnitude of the Eruption: The scale and intensity of the eruption determine the amount of lava, ash, and gases released.
  3. Proximity to Populated Areas: Volcanoes near densely populated areas can cause more casualties and property damage.
  4. Prevailing Wind Direction: The direction of the wind can carry ash and gases toward or away from populated areas, affecting air quality and visibility.
  5. Preparedness and Early Warning Systems: Communities with better preparedness and warning systems can minimize the loss of life and property.
  6. Geology and Topography: The local geology and landscape can influence the flow of lava and the spread of ash, affecting the areas impacted.
  7. Volcano’s History: Understanding a volcano’s previous eruption patterns may help predict its behaviour and potential impact.
  8. Climate and Weather Conditions: Weather can affect the dispersal of volcanic materials and the subsequent secondary effects, such as mudflows.
  9. Secondary Hazards: These might include lahars, pyroclastic flows, landslides, tsunamis (if near a body of water), and acid rain, which can have wide-reaching impacts.
  10. Economic Factors: Wealthier areas might have better infrastructure and resources to cope with a volcanic eruption, whereas poorer areas may suffer more.
  11. Time of Eruption: Similar to earthquakes, the time of day can affect the response and impact (e.g., nighttime eruptions may catch people unawares).
  12. Health: The local population’s health can also affect the impact of volcanic eruptions. High incidences of respiratory conditions and other health problems can exacerbate the effect on the local population.


  • Primary and Secondary Effects

    Primary effects include immediate damage like the collapse of structures, while secondary effects include subsequent consequences such as fires from ruptured gas lines or long-term homelessness.

  • Human and Infrastructure Impact

    Earthquakes and volcanic eruptions can lead to loss of life, destruction of buildings, loss of jobs and businesses, and damage to transport networks, power, and water supply.

  • Environmental Consequences

    Volcanoes and earthquakes can cause environmental damage like loss of vegetation and habitats, effects on climate, and closure of airports due to ash clouds.

  • Factors Influencing Impact

    Various factors such as strength, depth, proximity to populated areas, quality of building materials, and preparedness can affect the overall impact of both earthquakes and volcanic eruptions.

  • Unique Effects of Volcanoes

    Unlike earthquakes, volcanic eruptions can affect areas hundreds of miles away and have unique impacts such as lahars, pyroclastic flows, acid rain, and global climate effects.


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