Report on Kusatsu-Shiranesan (Japan) — October 1983
Scientific Event Alert Network Bulletin, vol. 8, no. 10 (October 1983)
Managing Editor: Lindsay McClelland.
Kusatsu-Shiranesan (Japan) Explosions eject large tephra
Please cite this report as:
Global Volcanism Program, 1983. Report on Kusatsu-Shiranesan (Japan) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 8:10. Smithsonian Institution.
36.618°N, 138.528°E; summit elev. 2165 m
All times are local (unless otherwise noted)
UPI reported that thunderous explosions ejected tephra on 13 November at 1144. [Blocks fell a few hundred meters from the vent; original press reports of a more distant fall of large tephra were incorrect.] Tephra [reached a town] (Nakanojo) 40 km SE of the volcano. A "secondary" eruption occurred 25 minutes later. No injuries were reported.
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: UPI.