Mount Fuji, towering at 3,776 meters, is Japan's highest mountain. For centuries it has been worshiped as a sacred mountain and is still a magnet for hundreds of thousands of tourists every year. 

Mount Fuji is an active volcano, last erupting in 1707. Sixteen days of rumbling released some 800 million cubic meters of volcanic ash which accumulated in layers about 4 centimeters thick in the city of Edo, present-day central Tokyo.

A Mount Fuji disaster management council simulated what would happen if an eruption of that scale were to occur today, covering the greater Tokyo area with volcanic ash.

The council announced Monday that if Mount Fuji erupts on a large scale in the future, the pyroclastic flow would chop off major roads used for evacuation, leading to water and power cuts and disruptions to traffic and logistics in the capital circle within hours, according to a report by the Japan Times newspaper. 

According to the report, the reassessment assumed three cases with different wind directions, based on the 1707 eruption.

The worst scenario would happen when the wind blows from the southwest during the eruption of Mount Fuji. Given the situation, the hot gas could travel some four kilometers further than previously forecast. In some areas, the volcano ash would accumulate in layers as thick as 30 centimeters, and wooden houses could collapse.

The reassessment showed that parts of the Higashifujigoko toll road connecting Fujiyoshida and Shizuoka's Oyama, as well as the Mount Fuji Skyline road connecting Fujinomiya and Gotemba within Shizuoka, could be destroyed.

The program's chief examiner, Fujii Toshitsugu, an honorary professor at Tokyo University, said it is difficult to predict an eruption and its aftermath.

"If the response is not quick enough, tens of millions of people will be trapped and the circulation of materials will be completely blocked," said Toshitsugu. "So it's very important to come up with a response plan in advance."