Report on Iwatesan (Japan) — November 1996
Bulletin of the Global Volcanism Network, vol. 21, no. 11 (November 1996)
Managing Editor: Richard Wunderman.
Iwatesan (Japan) Microearthquakes and tremor
Please cite this report as:
Global Volcanism Program, 1996. Report on Iwatesan (Japan). In: Wunderman, R. (ed.), Bulletin of the Global Volcanism Network, 21:11. Smithsonian Institution.
39.853°N, 141.001°E; summit elev. 2038 m
All times are local (unless otherwise noted)
On 11 September, 2 October, and 24 and 25 November, shallow volcanic microearthquakes were recorded below Iwate. On 12 September and 11 October small-amplitude volcanic tremors were observed.
Geologic Background. Viewed from the east, Iwatesan volcano has a symmetrical profile that invites comparison with Fuji, but on the west an older cone is visible containing an oval-shaped, 1.8 x 3 km caldera. After the growth of Nishi-Iwate volcano beginning about 700,000 years ago, activity migrated eastward to form Higashi-Iwate volcano. Iwate has collapsed seven times during the past 230,000 years, most recently between 739 and 1615 CE. The dominantly basaltic summit cone of Higashi-Iwate volcano, Yakushidake, is truncated by a 500-m-wide crater. It rises well above and buries the eastern rim of the caldera, which is breached by a narrow gorge on the NW. A central cone containing a 500-m-wide crater partially filled by a lake is located in the center of the oval-shaped caldera. A young lava flow from Yakushidake descended into the caldera, and a fresh-looking lava flow from the 1732 eruption traveled down the NE flank.
Information Contacts: Volcanological Division, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan.