Report on Kusatsu-Shiranesan (Japan) — January 1991
Bulletin of the Global Volcanism Network, vol. 16, no. 1 (January 1991)
Managing Editor: Lindsay McClelland.
Kusatsu-Shiranesan (Japan) Continued seismicity but no change in surface activity
Please cite this report as:
Global Volcanism Program, 1991. Report on Kusatsu-Shiranesan (Japan) (McClelland, L., ed.). Bulletin of the Global Volcanism Network, 16:1. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199101-283120
36.618°N, 138.528°E; summit elev. 2165 m
All times are local (unless otherwise noted)
Seismicity has remained at high levels since February 1990. During January, 92 earthquakes and 24 volcanic tremor episodes were recorded . . . . No changes in surface activity were observed. Similar activity was noted in early February.
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.