Case study - volcanic eruption - Mt Merapi, Indonesia 2010


Mt Merapi is on the island of Java, in the Indian Ocean.

Mt Merapi (meaning Mountain of Fire) is an active stratovolcano (or composite volcano) located in South East Asia, on the island of Java, Indonesia. It is the most active volcano in Indonesia, having erupted regularly since 1548.

Merapi is located in one of the most densely populated parts of Java with over 11,000 people living on the slopes of the mountain. Most of these people are poor farmers who depend on the richness of the soil for their living.

In March 2010 there were the first signs that the volcano would erupt. Tiltmeters showed that the volcanic dome had begun to bulge. In September there was increased earthquake activity and white plumes of smoke were seen rising above the volcano's crater. On Monday 25th October 2010, Merapi erupted and continued to erupt until 30th November.


Mount Merapi
Mount Merapi

The volcano and its eruptions were caused by the Indo-Australian Plate being subducted beneath the Eurasian Plate. The volcano is located on a destructive plate margin, at a subduction zone, part of the Pacific Ring of Fire.

Short-term effects


  • Volcanic bombs and heat clouds, with temperatures up to 800°C, spread over a distance of 10 km.
  • Pyroclastic flows travelled 3 km down the heavily populated mountain sides.
  • Volcanic ash fell up to 30 km away and travelled 6 km into the sky.
  • Villages, such as Bronggang, 15 km from the volcano, were buried under 30 cm of ash.
  • Sulphur dioxide was blown across Indonesia, the Indian Ocean and as far south as Australia.


  • Ash clouds caused major disruption to aviation across the region.
  • Roads were blocked with cars and motorcycles as residents tried to flee the hazard zone.
  • Vegetable prices increased because of the damage to crops.
  • 350,000 people living in the area had to flee their homes.
  • Heavy rain on 4th November caused lahars, washing ash and rock down into towns and destroying bridges.
  • Schools were closed.
Ash cloud from Mount Merapi eruption
Ash cloud from Mount Merapi eruption

Long-term effects


  • Ash will eventually lead to more fertile soils in the area.
  • New data from the eruption has enabled hazard mapping to be updated and used to set up exclusion zones around the volcano.


  • 353 people were killed and 577 people were injured.
  • Overcrowded evacuation centres led to poor sanitation, no privacy and a serious risk of disease.
  • People, particularly farmers, lost their homes and livelihoods.
  • 350,000 people were made homeless.



  • 210 evacuation centres were set up in schools, churches, stadiums and government offices.
  • An exclusion zone of 20 km was established around the volcano.
  • Indonesian Disaster Management Agency mobilised volunteers, the military and police to circulate information, rescue survivors, control traffic, set up makeshift hospitals and kitchens in evacuation centres.
  • International aid was offered from governments and non-governmental organisations (NGOs) such as the Red Cross and Red Crescent.


  • 2,682 people were moved to new, safer houses permanently.
  • The government made money available to farmers to help replace their livestock.
  • The government set up a special task force to support people who were affected by the volcano, either by family issues, or because they lost their jobs.
  • An ongoing exclusion zone of 2.5 km was set up settling people in areas of lower risk.
  • Improved prediction measures and education in evacuation procedures have been introduced.
  • Dams have been built in valleys to hold back lahars.
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