Report on Kusatsu-Shiranesan (Japan) — July 1990
Bulletin of the Global Volcanism Network, vol. 15, no. 7 (July 1990)
Managing Editor: Lindsay McClelland.
Kusatsu-Shiranesan (Japan) More frequent volcanic earthquakes and tremor
Please cite this report as:
Global Volcanism Program, 1990. Report on Kusatsu-Shiranesan (Japan) (McClelland, L., ed.). Bulletin of the Global Volcanism Network, 15:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199007-283120
36.618°N, 138.528°E; summit elev. 2165 m
All times are local (unless otherwise noted)
The number of volcanic earthquakes . . . remained at high levels as of 8 August, with 212 earthquakes in June and  in July. Twelve volcanic tremor episodes were recorded by the seismograph 1.1 km NE of Yugama Crater.
Geological Summary. The Kusatsu-Shiranesan complex, located immediately north of Asama volcano, consists of a series of overlapping pyroclastic cones and three crater lakes. The andesitic-to-dacitic volcano was formed in three eruptive stages beginning in the early to mid-Pleistocene. The Pleistocene Oshi pyroclastic flow produced extensive welded tuffs and non-welded pumice that covers much of the E, S, and SW flanks. The latest eruptive stage began about 14,000 years ago. Historical eruptions have consisted of phreatic explosions from the acidic crater lakes or their margins. Fumaroles and hot springs that dot the flanks have strongly acidified many rivers draining from the volcano. The crater was the site of active sulfur mining for many years during the 19th and 20th centuries.
Information Contacts: JMA.