History and Future of Volcanic Disasters in and Around the Tokyo Metropolitan Area, Central Japan

Abstract

This chapter reviews historical volcanic disasters that affected the Tokyo metropolitan area and its surroundings in Central Japan. It discusses the danger of volcanic disasters that will occur in the future. The 1707 (Hoei) eruption of the Fuji volcano, the 1783 (Tenmei) eruption of the Asama volcano, and the so-called Kanto Loam, volcanic soil deposits containing many Holocene to Pleistocene fall-out tephras, suggest the potential hazards from such volcanic activities. The small to moderate eruptions (VEI 1 to 2) that occurred at the Asama volcano resulted in minor ash falls in and around Tokyo a few times in every one to two decades. The Asama volcano will probably cause minor ash falls in the near future. Volcanic disasters from larger, but rarer, eruptions, rated VEI 4 to 5, are also considered, referring to the 1707 (Hoei) eruption of the Fuji volcano and the measures and predictions of the next Fuji eruption. This chapter notes not only disasters caused by ash falls but also those caused by lahars along the Tone, Edo, Sakawa, and Sagami Rivers connecting the Asama, Haruna, and Fuji volcanoes, as landform developments in these areas in the Holocene and historical disasters suggest that these drainage basins have the potential for lahar disasters. The impacts and frequencies of more severe eruptions, rated VEI 6 to 7, are considered by referring to geological records of air-fall tephras and/or pyroclastic flow deposits, such as the VEI 6 Hakone-Tokyo tephra (ca. 66 ka) and the VEI 7 Aira-Tn tephra (ca. 30 ka).