Report on Fujisan (Japan) — 17 January-23 January 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 17 January-23 January 2001
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2001. Report on Fujisan (Japan). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 17 January-23 January 2001. Smithsonian Institution and US Geological Survey.
35.361°N, 138.728°E; summit elev. 3776 m
All times are local (unless otherwise noted)
Several news reports have noted abnormally high earthquake activity during the past several months at Fuji. Usually 1 to 2 low-frequency earthquakes per month are recorded; but recent monthly counts were 35 for September 2000, 133 for October, 222 for November, and 143 for December. No other measured parameters changed at the volcano. While the earthquake counts are abnormally high, scientists do not believe that they are indicative of an imminent eruption. The volcano is being carefully monitored.
Geologic Background. The conical form of Fujisan, Japan's highest and most noted volcano, belies its complex origin. The modern postglacial stratovolcano is constructed above a group of overlapping volcanoes, remnants of which form irregularities on Fuji's profile. Growth of the Younger Fuji volcano began with a period of voluminous lava flows from 11,000 to 8000 years before present (BP), accounting for four-fifths of the volume of the Younger Fuji volcano. Minor explosive eruptions dominated activity from 8000 to 4500 BP, with another period of major lava flows occurring from 4500 to 3000 BP. Subsequently, intermittent major explosive eruptions occurred, with subordinate lava flows and small pyroclastic flows. Summit eruptions dominated from 3000 to 2000 BP, after which flank vents were active. The extensive basaltic lava flows from the summit and some of the more than 100 flank cones and vents blocked drainages against the Tertiary Misaka Mountains on the north side of the volcano, forming the Fuji Five Lakes, popular resort destinations. The last confirmed eruption of this dominantly basaltic volcano in 1707 was Fuji's largest during historical time. It deposited ash on Edo (Tokyo) and formed a large new crater on the east flank.