Causes and Effects

This needs a case study to describe and explain the causes and effects on the people and environment.

The effects of a volcanic eruption and earthquake are separated into three categories:

  • Environmental
  • Economic*
  • Social*

*When talking about 'human' impacts we refer to both economic and social.

Specific case study used here:

Si Chuan Earthquake May 12th, 2008 14:28

Causes, including characteristics of the earthquake, type of plate boundary

  • Collision between the Indo-Australian and Eurasian tectonic plates
  • Indo-Australian plate travels North 5cm per year
  • Crust is trying to flow away, move East
  • Thrust fault created
  • Slip of Longmenshan fault created Longmenshan fold mountains
  • Longmenshan fault moved up to 13m in quake
  • Land also moved 3m higher up
  • Weak, fractured rocks
  • Focus only at 19km below surface
  • Rated as X (10) on the Mercalli Intensity scale in mountainous areas
  • Steep, complex topography
  • Earthquake of 8.0 magnitude on Richter Scale

Impacts: Environmental (facts included)

  1. Large Amount of rainfall weakened rocks and in effect, caused landslides and rockfalls
  2. Ecosystem degradation and agricultural disturbance.
  3. The habitats for many animals (eg. Pandas) are destroyed (no bamboo = no food = starvation = death). The animals may become extinct.
  4. Reservoirs, hydropower stations, lakes all have ‘major safety issues’

Impacts: Human (Economic/social, include facts)

  1. Close to 5 million people were left homeless (5,000,000)
  2. SiChuan is one of the major agricultural production bases of China. China suffers from the loss of farm output in Si Chuan (rice and pork are on short supplies)
  3. SiChuan and China lost a large number of talented people such as engineers.
  4. There were 6000 deaths of children and China’s one-child policy means it will be difficult to return to the way it was before.
  5. Loss of hydroelectric facilities (classed as hazardous)
  6. Approx 70000 died and 19000 were missing, although 87000 were dead or missing

Reasons for the extent of impact:

  1. Densely populated area
  2. The focus of the earthquake was near the earth’s surface (19-26km)
  3. Landslides and intense rainfall prevented the rescue crew from entering villages
  4. Strong aftershocks, some exceeded a Mw 6.0 on the Richter scale
  5. The fault moved up to 13m in the quake

Link between environmental and human impacts

Big landslides, rockfalls heavy rain and aftershocks prevented the rescue crew from reaching villagers. The delay may have caused more deaths.

There were agricultural disturbances where the crops were destroyed. People in SiChuan are mostly farmers and they make a living through selling these crops. “Now they have nothing to sell, this will definitely have an impact on China’s (national) GDP.