WHAT CAN TOKYO EXPECT FROM A MT. FUJI ERUPTION?

A volcano is an accident waiting to happen and Mt. Fuji, the sleeping giant that lurks on the Tokyo skyline, is a pretty big accident. Eventually, maybe sometime soon, maybe tomorrow, she's gonna blow, and when she does what kind of impact is that going to have on the mega-city of 35 million souls nestling in its shadow? 

Luckily, we have wonks and boffins working on this disaster scenario to tell us what to expect, and there are also detailed emergency plans signed off by the Japanese government at the highest level. 

As reported by the Asahi Shimbun: 

"All residents in the zone from Mount Fuji to Sagamihara, Kanagawa Prefecture, just west of Tokyo, should evacuate in the event of a major volcanic eruption at Japan’s tallest peak, an expert panel said.

That area, which would receive at least 30 centimeters of ash from a major Mount Fuji eruption, is considered the most dangerous on a four-stage classification scale, according to the panel organized by the Cabinet Office.

In most other areas, residents would be urged to remain at home since electricity, transportation and communications would likely be severely hampered, according to the panel’s evacuation guidelines compiled on March 21."

As the map below shows, the most at-risk areas would be a relatively sparsely inhabited zone in North West Kanagawa Prefecture, but also a much wider and more heavily-populated area of central Tokyo would be at risk of volcanic ash of between 3 cm and 30 cm. 

In the red areas (designated as stage 4 areas) all residents would be advised to evacuate. In the orange areas (designated as stage 3 areas) all residents would be warned that ash accumulated on roads could disrupt transportation and prevent deliveries of adequate supplies. They are advised to store food, water, toilet paper and other supplies to last for at least one week.

The ash is also expected to interfere with rail travel and electricity supplies:

"Railways are especially vulnerable because even a few millimeters of ash on tracks would stop train operations, bringing public transportation in the greater Tokyo area to a halt.

East Japan Railway Co. has 44 vehicles with brushes to clear tracks, but it is not known if the equipment would be of use after a volcanic eruption.

Electric power could also be hampered if volcanic ash should become entrapped in filters at thermal-powered plants. Blackouts could occur if ash mixed with moisture accumulated on power lines or poles."

All this disaster prep is entirely necessary. Over the past 5,600 years, Mount Fuji has erupted 180 times. It is a question of when not if.