Mount Ontake

• Honshu


  Main island of Japan
• Event

  27th September 2014
• 250 hikers
• Mount Ontake


  Second highest volcano in Japan at 3067 m
• Until 1979, Mount Ontake was said to be dormant and then underwent minor eruptions in 1991 and 2007
• Mount Ontake erupted in 2014 without warning, despite being a monitored volcano
• Japan

  • Lies at the junction of 4 major plate boundaries: Pacific, Philippine, Eurasian, North American
  • Subduction of the Pacific plate under the North American and Philippine plate, and the subduction of the Philippine plate beneath the Eurasian plate
• There are 100 active stratovolcanoes on the Japanese islands
• Phreatic eruption


  Water seeped into the volcano and became superheated by the magma
• Hot ash, rocks and steam were ejected and did not involve the eruption of any magma
• Eruption


  1. Pyroclastic flow

  2. Trapped 250 people

  3. Over 50 deaths

  4. 40 others injured with cuts, bruises, broken bones and lung damage

  5. 57 missing
• Heavy, toxic volcanic ash 450 cm thick for 3km, engulfing hikers
• Volcanic rocks fell
• Reduced visibility, hikers left in complete darkness
• Poisonous levels of hydrogen sulphide
• 1000 Japanese workers set out to search
• Those brought down the mountain received emergency medical attention
• People had photographs of the eruption
• The eruption was steam and ash, rather than magma which made it harder to predict
• There were no visible warnings such as changes to the mountain surface or earth movements