Impacts of Tectonic Hazards » Impacts of Earthquakes and Volcanic Eruptions

Impacts of earthquakes

An earthquake is a hazard. The harm it does to people, property and the environment is its impact. Geographers sort impacts in two ways. First by when they happen, and then by who or what they affect.

Key terms:

• Primary impact: damage caused directly by the shaking of the ground, at the time of the earthquake.
• Secondary impact: damage caused by something the earthquake sets off, hours, days or weeks later.
• Liquefaction: when shaking turns wet, loose soil into a runny liquid that can no longer hold up buildings.
• Social impacts: effects on people's lives, such as deaths, injuries and homelessness.
• Economic impacts: effects on money, jobs, businesses and the cost of repairs.
• Environmental impacts: effects on the natural world, such as landslides and damaged land.

Secondary impacts explained

• Fires: broken gas pipes and electricity cables start fires. Broken water pipes mean firefighters have no water. In Kobe, Japan, in 1995, fires burned large parts of the city after the earthquake.
• Landslides: shaking loosens steep slopes, which can bury roads and villages.
• Liquefaction: buildings tilt and sink into the ground. It was widespread in Christchurch, New Zealand, in 2011.
• Tsunamis: an earthquake under the sea can lift the sea floor and send giant waves to the coast. The 2011 earthquake off Japan caused a tsunami that killed many thousands of people.
• Disease: clean water and sewage pipes break, so illnesses such as cholera can spread.
• Homelessness: people sleep outside or in camps, often for months.
• Economic losses: repairs cost huge sums, shops and factories close and people lose their jobs.

Sorting impacts: social, economic, environmental

Type	Earthquake examples
Social	Deaths and injuries, homelessness, disease, schools and hospitals closed
Economic	Collapsed buildings and roads, lost jobs, damaged factories, cost of rebuilding, fall in tourism
Environmental	Landslides, cracks in the ground, damaged forests and farmland, flooded land after a tsunami

Impacts also happen at different scales. A collapsed house is a local impact. A damaged port that cannot export goods affects the whole country. Several nearby countries can be hit by the same tsunami (regional).

Impacts of volcanic eruptions

You met the hazards themselves in the lesson called Volcanic Hazards. Here we look at what they do to people and places. Eruption impacts can be short-term (during the eruption and the following days) or long-term (lasting years). Unlike earthquakes, eruptions also have clear positive impacts.

	Short-term	Long-term
Negative	Deaths and injuries. Homes and farmland buried or burned. Flights cancelled because ash can damage jet engines.	Farmland and homes take years to recover. Ash and gases in the air can cool the climate. Jobs are lost where farms and tourism are destroyed.
Positive	Tourists come to see an active volcano.	Fertile soils for farming. Tourism income. Geothermal energy.

Climate effects of ash and gases

In a large eruption, ash and gases such as sulphur dioxide rise high into the air and spread around the world. They reflect sunlight back to space, so the Earth cools for a while. The eruption of Tambora in Indonesia in 1815 was so large that 1816 became known as the 'year without a summer' in Europe and North America. Cold weather ruined crops and food became scarce. This was a global impact from one volcano.

Why impacts differ between LICs and HICs

The same hazard can cause very different impacts. Compare two earthquakes. In 2010 a magnitude 7.0 earthquake hit Haiti, an LIC, close to the capital Port-au-Prince. Over 100,000 people died. In 2011 a magnitude 6.3 earthquake hit Christchurch in New Zealand, an HIC. There were 185 deaths. The Haiti earthquake was the bigger of the two, but size is not the whole story. Christchurch was a strong, damaging earthquake too, yet far fewer people died. The difference was in the people and places hit.

Time of day matters too. At night most people are at home in bed, so homes that collapse kill many. In the day, people may be at work or school, so deaths depend on where those buildings are and how strong they are. Wealth also decides how fast a place recovers. HICs often have insurance and savings, but many people in LICs have neither.

Exam-style question

Fig. 1.1 gives made-up data for two earthquakes of the same magnitude.

	Country A (LIC)	Country B (HIC)
Magnitude	7.0	7.0
Deaths	12,000	40
Time	3 am	3 am
Buildings meeting earthquake codes	10%	90%

(a) Identify one secondary impact of an earthquake. [1 mark]

(b) Describe one social impact and one economic impact of an earthquake. [2 marks]

(c) Explain why the earthquake in Country A caused many more deaths than the one in Country B. [3 marks]

(d) Discuss the positive and negative impacts of volcanic eruptions. [6 marks]