Yukio HAYAKAWA and Hideko NAKAJIMA
abstract
The 1108 eruption of Asama is the largest among numerous eruptions of the volcano during the Holocene. The magnitude is twice as large as that of the notorious 1783 eruption, which killed about 1,400 people. It is also the oldest written eruption of Asama. Chuyuki, which was written in Kyoto, 300 km SW of Asama, describes that the eruption started on September 29, 1108, by the Julian calendar, and that fields of rice and other crops were severely damaged. Many fatalities are strongly suspected by the distribution of the Oiwake ignimbrite, but no description is given for human loss in Chuyuki. A thin pumice layer intercalated between the 1108 scoria and the 1783 pumice can be correlated to a record of Pele's hair-fall in Kyoto in 1596. As many as 800 fatalities at the summit in 1598 described in Todaiki cannot be true. Tenmei Shinjo Hen'iki, which describes that a number of villages along the Jabori River were swept away by hot lahars in 1532, is not a contemporary document. It was written in the late 18th century. Fifteen fatalities at the summit in 1721 can be true. After the 1783 eruption, Asama was relatively quiet for 100 years. During the early and middle 20th century, Asama was very active with a peak of 398 times vulcanian explosions in 1941. About 30 lives were lost at the summit, in the 20th century, by 12 explosions among the total about 3,000 explosions.
Table 1. A list of Reported eruptions of Asama, including dismissed reports.
Table 2. Sequence of the 1108 eruption of Asama reconstructed from Chuyuki and Denryaku
Table 3. Number of fatal explosions at Asama during the 20th century.
Full paper in Japanese, published in Bullettin of the Volcanological Society of Japan, 43（4），213-221