Mount Ontake Eruption Flashcards
Deaths
63; 31 near summit, 6 classed as missing
When did it happen
27th September 2014
what type of eruption was it
phreatic
what is a phreatic eruption
Subsurface or surface water is heated and converted to steam by hot magma underground, builds pressure due to thermal expansion which creates an explosion
VEI
3
Common cause of injury
injuries from tephra
What hazards were produced?
Ash falls, pyroclastic flows, tephra, lahars/ mudflows.
Why was the eruption not detected
It didn’t produce much seismic activity beforehand due to it being phreatic. 5 families of victims attempted to sue the Japanese government saying they should have raised the warning level.
What is a possibility why so many people died
Lack of warning and close proximity to climbers.
The volcano was known as safe and easy to climb - popular with tourists.
Eruption happened around lunchtime -people at the summit eating lunch
How far did the pyroclastic flow travel
2.5km along the valley at average speed of 32kmh
How many people were trapped on the slopes
250 people were trapped due to the pyroclastic flows
How much ash was produced
40-50cm of heavy toxic volcanic ash covered the mountain
What did ash falls cause?
Roofs collapsed under the weight
Killed plants as they couldn’t do photosynthesis causing habitat loss.
Respiratory issues for animals and humans.
how far away was the furthest tephra crater
almost 1km away
Who helped to rescue people?
500 firefighters and Japan self defence force.
why were rescue attempts disrupted
Release of toxic gases as well as threat of continued volcanic activities caused rescue attempts cancelled late September 2014
How destructive were the pyroclastic flows
Flows were not thought to be very destructive due to lack of burnt/fallen trees
Why do people live near Mount Ontake
Geothermal energy, mineral rich soil for farming, tourism is good for businesses.
Economic impacts
Long term decline in tourism led to businesses closing down.
Lots of farmland was damaged.
Ski resorts shut down.
Social responses
Airport, expressway and trains closed
School children given hard hats
Gas masks given out
Economic responses
Removal of ash from farmland
Insurance pay-outs of up to ¥300,000
Repaired infrastructure
What did Japan do to reduce future impacts
Improved evacuation plans, drills done in nearby schools
Safety packs given to climbers, concrete bunkers built for protection from tephra
Built lava diversion
Increased monitoring of volcano and gas levels.
