Potential Offshore Dumping of Volcanic Ash: Japanese Government's Contingency Plans
In preparation for the possibility of a large-scale eruption of Mount Fuji akin to the 1707 Hoei eruption, the Japanese government is contemplating strategies for handling the significant ash deposits, including the consideration of offshore dumping. The key concern is the potential shortage of land for temporary storage, prompting the exploration of ocean dumping as a viable solution.
Japan's Marine Pollution Prevention Law generally prohibits the disposal of waste into the sea; however, exceptions are made in cases of environmental urgency. The government is contemplating this measure as part of its response to the potential eruption of Mount Fuji.
While some experts argue that volcanic ash is a naturally occurring substance with minimal environmental impact, the government plans to conduct thorough examinations of ash samples to assess its potential effects before making any decisions regarding offshore dumping.
The government intends to convene an expert meeting next month to discuss the offshore dumping of volcanic ash and aims to incorporate the outcomes into guidelines for volcanic ash management, expected to be formulated next spring.
If Mount Fuji were to erupt on a scale similar to the 1707 eruption, estimates suggest that the volume of ash generated would be ten times greater than the amount of disaster waste produced during the 2011 Great East Japan Earthquake. The projected amount of ash to be removed is a staggering 490 million cubic meters, equivalent to 390 Tokyo Dome buildings with a volume of approximately 1.24 million cubic meters and covering an area of about 47,000 square meters.
In the event of an eruption, central Tokyo could accumulate approximately 10 centimeters of ash over two weeks, while Kanagawa and Yamanashi prefectures, in close proximity to Mount Fuji, may experience an accumulation of over 30 centimeters.
Mount Fuji, having remained dormant since its last significant ash emission in December 1707, presents a unique challenge due to its extended period of inactivity. The government emphasizes the historical significance of this potential eruption, noting that it would be the longest gap between eruptions in over 5,000 years, highlighting the need for comprehensive contingency plans.
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