Mt Ontake Flashcards
Tectonic Setting
Volcano in Japan (MEDC) near a ski resort
200km west from Tokyo
Destructive/Convergent plate margin
Stratovolcano over 3000m high
It was dormant until a series of eruptions from 1979 to 1980
Phreatic eruptions occurred in 1991 and 2007
Phreatic Eruptions
Steam-blast eruption occurs when magma heats ground or surface water
Magma reaches extreme temperatures of up to 1,200 degrees Celsius
This causes near-instantaneous evaporation
Results in explosion of steam, ash, water, rock and volcanic bombs
It can be accompanied by gases such as Carbon Dioxide and Hydrogen Sulphide. Hydrogen Sulphide is poisonous and can lead to asphyxiation in sufficient concentration
Effects
63 deaths with 6 buried in ash
Dozens were injured due to debris and tephra
Ski resorts had to be closed for the season preventing tourism
Raicho bird population of 513 decimated and is at risk of extinction
Vegetation vital for the survival of bird species was killed by 10cm of ash at 2700m
Ash covered large areas of land
Prediction
Was not really predicted
The JMA detected 85 earthquakes prior to the eruption
Tiltmeters and 12 seiographs were set up by the JMA to monitor the volcano - results provided insufficient evidence in support of an eruption
Had gasmeters been implemented they may have helped prediction
Prevention
A 4km exclusion zone was set up after the eruption - failed to prevent 57 deaths
The zone kept the local population safe from eruption effects
There was failure to prevent effects on air travel
Overall, prevention was partially successful, but only on a local scale
Responses
Search and Rescue operations were set up, with 1,000 troops
In October 2014, Typhoon Phanfane hit, rendering the search and rescue missions unsuccessful
Responses to the eruption were adequate, however halted by an unavoidable natural hazard
Had the typhoon not hit, responses would have been far more effective in mitigating effects
