Ash could paralyze Tokyo if Mount Fuji erupts, government report warns


A hypothetical eruption of Mount Fuji, Japan’s tallest peak, could rain volcanic ash on Tokyo and push the capital into a state of paralysis, according to a government report obtained by Kyodo News.

The report will become the basis for drawing up a contingency plan for such a scenario, which may include evacuating residents and deploying bulldozers to clear roads.

Mount Fuji is an active volcano lying about 100 kilometers from central Tokyo. Historical records show it has experienced at least 10 large-scale eruptions since 781, though three centuries have passed since the last time it ejected material and it has shown no signs of volcanic activity since the 1960s.

According to the report obtained Monday, more than 10 centimeters of ash could fall on Tokyo’s 23 wards over a span of weeks, rendering roads useless and stopping the flow of goods and people to, from, and within the metropolis — home to a population of more than 9 million in the city proper.

Just 0.5 cm of ash could begin to cause mechanical problems for cars and have adverse health effects, particularly for the eyes and lungs. More than 1 cm could cause mass power outages and water filtration systems to fail, the report warns.

The government has considers it necessary to remove ash to ensure that roads won’t close down, and is expected to debate where to store heavy machinery for the purpose.

In the past the government had drafted a map showing that three prefectures in Kanagawa, Yamanashi and Shizuoka surrounding Mount Fuji could see up to 50 cm of volcanic ash, while 10 to 20 cm of ash could fall outside those areas.

The government has estimated previously that an eruption could result in damage and losses worth over ¥2.5 trillion ($23 billion).

“But if we include the impact on aviation and other transportation as well as secondary infrastructure, the cost could be far more than two trillion yen,” said Toshiyasu Nagao, head of Tokai University’s Earthquake Prediction Research Center.

Japan lies on the Pacific “Ring of Fire” and is home to 111 active volcanoes, according to the national meteorological agency.

Another peak, Mount Shinmoe on the island of Kyushu, has been erupting in fits and starts since early March, blanketing the surrounding area in a layer of ash and dealing a blow to local agriculture and tourism industries.

In April, Mount Io, also on Kyushu, erupted for the first time in 250 years.