Mount Ontake Eruption Flashcards

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1
Q

Deaths

A

63; 31 near summit, 6 classed as missing

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1
Q

When did it happen

A

27th September 2014

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2
Q

what type of eruption was it

A

phreatic

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3
Q

what is a phreatic eruption

A

Subsurface or surface water is heated and converted to steam by hot magma underground, builds pressure due to thermal expansion which creates an explosion

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4
Q

VEI

A

3

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5
Q

Common cause of injury

A

injuries from tephra

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6
Q

What hazards were produced?

A

Ash falls, pyroclastic flows, tephra, lahars/ mudflows.

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7
Q

Why was the eruption not detected

A

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.

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8
Q

What is a possibility why so many people died

A

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

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9
Q

How far did the pyroclastic flow travel

A

2.5km along the valley at average speed of 32kmh

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10
Q

How many people were trapped on the slopes

A

250 people were trapped due to the pyroclastic flows

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11
Q

How much ash was produced

A

40-50cm of heavy toxic volcanic ash covered the mountain

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12
Q

What did ash falls cause?

A

Roofs collapsed under the weight
Killed plants as they couldn’t do photosynthesis causing habitat loss.
Respiratory issues for animals and humans.

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13
Q

how far away was the furthest tephra crater

A

almost 1km away

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14
Q

Who helped to rescue people?

A

500 firefighters and Japan self defence force.

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15
Q

why were rescue attempts disrupted

A

Release of toxic gases as well as threat of continued volcanic activities caused rescue attempts cancelled late September 2014

16
Q

How destructive were the pyroclastic flows

A

Flows were not thought to be very destructive due to lack of burnt/fallen trees

17
Q

Why do people live near Mount Ontake

A

Geothermal energy, mineral rich soil for farming, tourism is good for businesses.

18
Q

Economic impacts

A

Long term decline in tourism led to businesses closing down.
Lots of farmland was damaged.
Ski resorts shut down.

19
Q

Social responses

A

Airport, expressway and trains closed
School children given hard hats
Gas masks given out

20
Q

Economic responses

A

Removal of ash from farmland
Insurance pay-outs of up to ¥300,000
Repaired infrastructure

21
Q

What did Japan do to reduce future impacts

A

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.