Effects of Earthquakes & Volcanic Eruptions
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
| Primary | Secondary | |
| Earthquake |
Ground Shaking Surface rupture |
Liquefaction Landslides Tsunami Fires |
| Volcanic Eruption |
Pyroclastic flow Lava flow Volcanic Bombs Lahars (mudflow) Earthquakes Direct ash fall |
Landslides Tsunami Acid rain Ash fallout from the atmosphere |
Factors affecting the impacts of earthquakes and volcanic eruptions
- All earthquakes and volcanic eruptions are unique
- The impacts that they have depend on a range of factors both human and physical
| Human | Physical | |
| Earthquake |
Building construction and design - poorly constructed buildings with poor quality building materials are more likely to collapse. Higher buildings amplify the shockwaves and are more likely to collapse Building density - where buildings are close together, they are more likely to damage or destroy other buildings if they fall Population density - the higher the density population the more people are likely to be injured or killed Preparation - earthquake drills can reduce the impact |
Magnitude - the amount of energy released by the earthquake. Usually, the higher the magnitude the greater the impact Geology - some rocks are more prone to liquefaction others provide stronger foundations for buildings Distance from the epicentre - the closer somewhere is to the epicentre the stronger the shock waves will be Depth - shallower earthquakes mean less energy is absorbed by the crust before the shockwaves reach the surface |
| Volcanic Eruption |
Proximity of population - how close populations are to the volcano. The nearer that people are the more likely they are to be affected by lava flow and ash Planning and preparation - where authorities have planned exclusion zones and evacuation plans the impact may be reduced |
Magnitude - the size and strength of the eruption. Usually, the higher the magnitude the greater the impact Type of volcano - composite (strato-volcanoes) tend to be more explosive and less predictable than shield volcanoes Amount of ash ejected into the atmosphere - ash in the atmosphere can impact on areas 100s of km away and can affect the global climate |
Effects of earthquakes and volcanic eruptions
- Although the characteristics of earthquakes and volcanic eruptions are very different many of the impacts are similar
- Impacts include:
- Loss of life and injury - this may be immediate through falling buildings or ash fall. Alternatively, it may be in the days and weeks after the event due to unclean water or disease
- Collapse or destruction of buildings - this leads to people being homeless for months and even years after the event
- Transport network - roads, bridges and railways may be damaged or destroyed. This can impact on the speed which aid can get to affected areas
- Loss of jobs and businesses - this impacts the economy when factories and offices are destroyed or damaged
- Loss of crops - leads to food shortages and affects farmers income
- Power and water supply damaged - this affects the supply of clean water
- Damage to the environment - loss of vegetation and habitats, effects on climate of ash
- Closure of airports - it is dangerous for jet planes to fly through ash clouds due to possible engine failure, so flights are cancelled
Exam Tip
It is easy to confuse the primary and secondary effects/impacts for earthquakes and volcanic eruptions. Remember:
- Primary effects are those which occur as a direct result of the earthquake or volcanic eruption. For example, buildings collapsing is a direct result of the earthquake ground shaking.
- Secondary effects are those things which result from the primary hazards. For example, fires caused by gas mains which have fractured.
Worked example
Study Fig 1, which shows information about the problems faced by households after an earthquake in Port-au-Prince, Haiti.
[5]
Fig 1
(i) Identify the two main problems caused by the earthquake in Haiti
[2]
-
Answer:
- Lack of shelter [1]
- Shortage of food [1]
(ii) Explain why it is necessary to provide clean water and sanitation after an earthquake.
[3]
- Answer:
- People need clean water supply/water to drink/to live/survive/prevent
dehydration [1] - Water/sewage pipes/water treatment stations will be cut off/damaged/broken [1]
- No running water [1]
- People cannot wash/bath/shower [1]
- No flush toilets [1]
- Sewage will spill out/contaminate (water supplies/area) [1]
- Disease/germs from dirty/polluted water or people sick from dirty water/waterborne diseases/examples of such as cholera [1]
- People need clean water supply/water to drink/to live/survive/prevent
