If Mount Fuji Blows Up, Are You Prepared?

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If there is a major eruption of Mount Fuji, the Tokyo metropolitan area could be smothered by a large amount of volcanic ash. A Cabinet Office study group has published a basic policy to reduce damage from such a cataclysmic event.

Mount Fuji is an active volcano that has erupted repeatedly in the past. It is easy to forget that fact since majestic Fuji-san has not erupted for more than three centuries. But it certainly will erupt again. It is important to grasp and apply that knowledge firmly in our disaster prevention efforts.

History and Potential

The largest eruption of Mount Fuji during the Edo period (1600-1868) was the Hoei Eruption. It lasted from mid-December 1707 until late February 1708.

Using that as its baseline, the expert study group predicts an eruption of the same size will spread volcanic ash more than three centimeters thick over a wide area, including central Tokyo. Areas closer to Mount Fuji will experience even more ash, reaching 30 centimeters in depth in nearby places.

Even a small amount of fallen ash can cause trains to stop running. And, if it rains after three centimeters or more of ash has accumulated, road travel will be limited to four-wheel vehicles and the transportation network will be paralyzed.

Other unfortunate consequences include the risk of airport closures, power outages, communication disruptions, and water shortages. Any of these could have a huge impact on society and the economy.

*The sun sets, turning the sky red behind Mount Fuji (©Sankei by Takumi Kamoshida)*

Prepare Before It's Urgent

Although an eruption does not appear to be imminent, now is the time for the national government, local governments, and companies to develop adequate measures to deal with such an eventuality. It is particularly important to remove volcanic ash quickly when it has accumulated on roads and in other areas. There needs to be a priority given to restoring transportation and logistics.

To do that, it will be necessary to establish storage sites ahead of time where the removed volcanic ash can be temporarily stored. Local governments should promptly select candidate sites.

There is also a need to develop technology to efficiently remove volcanic ash. The amount of volcanic ash that would need to be disposed of would be enough to fill 400 Tokyo Domes. Also, the final method of disposal must be considered.

Houses are not in danger of collapsing if less than 30 centimeters of ash falls on them. Therefore, most residents, except for those who require assistance, will not need to evacuate. Instead, they can continue living in their homes.

Be Prepared, Respond Calmly

In the event of an eruption, we all need to respond calmly. It is recommended that households stockpile enough water, food, and other essential items to last a week or more. That is the same as preparations for a major earthquake in the Tokyo metropolitan area.

It is difficult to predict when a major eruption of Mount Fuji will occur. The government should quickly develop estimates for the amount and distribution of ashfall after an eruption and disseminate information in an easy-to-understand manner.

Japan is one country where earthquakes and volcanic eruptions occur frequently, although large-scale volcanic eruptions are relatively rare. Nevertheless, we should steadily implement countermeasures to deal with volcanic ash while also preparing for earthquakes, floods, and other disasters. None of these can be put off until later.

There is no precedent anywhere in the world for a modern metropolis like Tokyo being affected by a large-scale volcanic eruption. If Japan’s efforts at disaster mitigation prove successful, that know-how could be useful in responding to volcanic eruptions in other countries as well.

Author: Editorial Board, The Sankei Shimbun

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