2024.05.01
Risk5: Volcanic eruption
The horror of an eruption
Looking back at the history of current eruptions of Mt. Fuji, various eruption phenomena have occurred, including lava flows, pyroclastic flows, scoria, volcanic ash, mountain collapse, eruptions of side volcanoes, and the generation of volcanic toxic gases. It is called the “Department Store of Eruptions.”
Phenomena related to eruptions
lava flow
A phenomenon in which underground magma erupts to the earth's surface as liquid lava and flows down. The flow is slow, and you can escape by running, but it will burn down anything in its path, whether it's a wooden building or a forest.
pyroclastic flow
A phenomenon in which a multiphase flow containing volcanic debris (volcanic ash, pumice, etc.) and gas components (water vapor, volcanic gas, etc.) at temperatures of several hundred degrees Celsius or higher flows down a mountainside at high speed. There is a risk of melting inside buildings and cars, making it unsafe. The most dangerous of all volcanic disasters.
phreatic eruption
A phenomenon in which groundwater is heated by high-temperature magma and evaporates rapidly, becoming high-temperature and high-pressure and causing an explosion. Although the scale of the eruption is classified as a small-scale eruption, the 2014 eruption of Mt. Ontake caused many casualties due to this phreatic eruption. Phreatic eruptions are difficult to predict compared to other forms of eruptions because signs of eruption cannot be detected by the movement of magma.
volcanic ash
Volcanic ash is made up of glass and mineral crystal fragments that were crushed and rapidly cooled when magma erupted, and is often hard and angular in shape. Inhaling volcanic ash can damage your lungs.
volcanic toxic gas
Volcanic gases containing highly toxic components such as hydrogen fluoride, hydrogen chloride, and sulfur dioxide may erupt. Volcanic gas components have a strong pungent odor and are easy to notice, but they can be dangerous if there is no visibility due to volcanic ash.
Reference) Japan Meteorological Agency HP, Cabinet Office Disaster Prevention Information HP, Fuji City HP Mt. Fuji eruption history/etc.
Eruptions do not necessarily start from the mountaintop.
Hoei eruption (1707)
The last eruption from the summit of Mt. Fuji was approximately 2,300 years ago. The Jogan eruption (864-866) was the largest eruption since then and created the Aokigahara Jukai, and the most recent eruption was the Hoei eruption (1707), which created the Hoei crater, which was larger than the summit crater. All eruptions occurred halfway up Mt. Fuji.
eruption hazard-map
eruption alert level
During normal times, the eruption alert level for Mt. Fuji is 1 (Potential for increased activity).
Even if the volcano is at eruption alert level 1, climbers above the 5th station must begin their descent when explanatory information (temporary) regarding the status of the volcano is announced.
Even if the volcano is at eruption alert level 1, climbers above the 5th station must begin their descent when explanatory information (temporary) regarding the status of the volcano is announced.
If an Volcanic Warning(Near the crater) or a.k.a. Near-crater Warning is issued, the alert level will be raised from 1 to 3 (Restriction on proximity to the volcano). All people in the first evacuation area, including the entire area above the 5th station, must evacuate. Tourists are asked to return home.
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Name |
Volcanic Alert Levels |
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Volcanic Warning(Residential area) |
Level 5 (Evacuation) * |
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Level 4 (Evacuation of the elderly, etc.) * |
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Volcanic Warning(Near the crater) |
Level 3 (Restriction on proximity to the volcano) |
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Level 2 (Restriction on proximity to the crater) *In the process of increasing volcanic activity, there is no alert level 2, and it is only used when it is lowered from level 3. |
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Volcanic Forecast |
Level 1 (Potential for increased activity) |
Prepare for an eruption
helmet
It is effective not only in the event of an eruption, but also in the event of falling rocks or falling down. Helmets can be rented for free on the Yoshida and Fujinomiya trails (2,000 yen deposit required for the Yoshida trail).
Yoshida Trail: Helmet Free Rental
At the 6th Station Safety Guidance Center, you can rent a helmet for free if you pay a deposit of 2,000 yen. (Limited number available)
Fujiyoshida Trail: Helmet Free Rental
At the 5th Station General Guidance Center, you can rent a helmet for free if you fill out the designated documents. (Limited number available)
goggles, mask
It is effective not only during eruptions, but also on dust when descending from a mountain.