Global environmental hazardsCase study

Indian Ocean Tsunami 2004

A very common case study for earthquakes is the South-East Asian tsunami of 2004. Other case studies include Mexico 1985, San Francisco 1989, Kobe 1995 and Pakistan 2005.

The underlying causes

On 26 December 2004 there was a massive and sudden movement of the Earth’s crust under the Indian Ocean. This earthquake was recorded at magnitude 9 on the Richter Scale and as it happened under the ocean, caused a devastating sea wave called a tsunami.

The epicentre of the earthquake occurred 200 kilometres west of the island of Sumatra in the Indian Ocean. The earthquake itself was caused by the subduction of the Indo-Australian plate under the Eurasian plate.

As the Indian plate (part of the Indo-Australian plate) moved underneath the Burma plate (part of the Eurasian plate) the crustal rocks stuck as they moved past one another. At 08:00 local time, the pressure build up was too great and the crustal rocks snapped, causing an earthquake.

When this happened the sea floor was pushed upwards displacing a huge volume of water and creating the devastating tsunami waves.

Impact on landscape and population

Landscape

• Some smaller islands in the Indian Ocean were completely destroyed.
• Coastal buildings were completely destroyed making people homeless.
• Fishing villages were completely destroyed.
• Lines of communication, including phone lines, were cut off.
• Electricity power lines were cut off.
• Roads and railways were destroyed.
• Fires broke out due to severed water pipes.

People

• Approximately 250,000 people are estimated to have been killed, including many tourists on the beaches of Thailand.
• There was an outbreak of diseases such as cholera due to a lack of fresh water supplies.
• There was a lack of food as many fish died and farms were destroyed.
• Thousands of people were made homeless.
• Thousands of people lost their jobs as tourist hotels in Thailand were destroyed and fishing vessels were washed ashore.