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Report on Etorofu-Yakeyama [Grozny Group] (Japan - administered by Russia) — February 1990

Etorofu-Yakeyama [Grozny Group]

Bulletin of the Global Volcanism Network, vol. 15, no. 2 (February 1990)
Managing Editor: Lindsay McClelland.

Etorofu-Yakeyama [Grozny Group] (Japan - administered by Russia) New fumaroles formed after predicted ash eruption in June

Please cite this report as:

Global Volcanism Program, 1990. Report on Etorofu-Yakeyama [Grozny Group] (Japan - administered by Russia) (McClelland, L., ed.). Bulletin of the Global Volcanism Network, 15:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199002-290070

Etorofu-Yakeyama [Grozny Group]

Japan - administered by Russia

45.012°N, 147.871°E; summit elev. 1158 m

All times are local (unless otherwise noted)

After the May 1989 activity, geologists performed aerial and field investigations at the request of local authorities. They forecast that vigorous fumarolic activity and rare weak explosions would continue through August, and this assessment was printed in the regional newspaper Suvorovsky Natisc on 15 June 1989, 4 days before the June eruption. Moderate fumarolic activity continued in June.

Seismic activity in a 100-m-wide zone extending NE across the volcano had increased March-May 1989. According to R.Z. Tarakanov, the earthquakes were at 30 and 60 km depths.

Aerial observations in August revealed a new group of fumaroles in the NNE part of the dome. During their 16 September ascent of the dome, Steinberg and Tkachenko measured gas temperatures of 100-104°C. Deep, narrow, craters had formed at the intersections of en-echelon fissures, and the surface around them was covered by andesitic ash (table 1). It is not yet known if the material was juvenile.

Table 1. Chemical analyses of ash samples collected from fissures in Ivan Grozny's summit dome. Analytical values are volume percent of dry gas. Courtesy of G. Steinberg.

Measurement Sample 9 Sample 10
Temp. (°C) 220 160
H2O (mole %) 92.2 96.6
CO2 83.36 49.88
H2S 12.63 21.85
SO2 2.45 2.40
H2 1.82 18.75
CO -- --
HCl 0.73 7.02
HF 0.01 0.11
CH4 0 0

Fumarolic activity was distributed along the summit crater fissure. Before the May explosions, emissions had been observed over the entire cross-section of the crater's fissure and on the E slope of the dome. No fumarolic activity was observed in August on the E outer slope of the dome, only from its uppermost W portion. The floor of the E part of the crater was covered with 30 cm of ash but exhibited no fumarolic activity.

At the request of the local authorities, geologists forecast (and published in the local newspaper Krasny Mayak on 28 September) that the volcano's activity should continue at its present level through February 1990.

Geological Summary. The Etorofu-Yakeyama (Ivan Grozny) complex is located in the center of Iturup Island. It has a 3-3.5 km diameter caldera open to the south, where a large extrusive andesitic dome was emplaced. Several other lava domes of Holocene age were constructed to the NE; extrusion of these domes has constricted a former lake in the northern side of the caldera to an extremely sinuous shoreline. Recorded eruptions, the first of which took place in 1968, have been from the central Yakeyama (Grozny) dome.

Information Contacts: G. Steinberg and R. Bulgakov, Yuzhno-Sakhalinsk.