Thursday, Jan 17, 2013
A thermal anomaly was detected over Kudriavy, a stratovolcano of the Medvezhia volcanic complex, on 11 January. Strong steam-and-gas plumes were also observed. [more]
Medvezhia volcanoThe Medvezhia volcano complex (including Medvezhii, Srednii, Kudryavyi, Kudriavy or Men’shoi Brat volcano) is one of the Kurile's most active volcanoes. It is located on the NE end of Iturup Island, Kurile Islands. It is remarkable for its high temperature fumaroles.
Medvezhia volcano has 2 overlapping calderas, 14 x 18 and 10 x 12 km in diameter, which were formed more than 10,000 years ago, and a row of 4 stratovolcanoes close to each other along a E-W line on the eastern side of the complex (from E to W): Medvezhii volcano, the highest and located outside the western caldera, Srednii, Tukap, and Kudriavy volcanoes.
All historic activity has been from Kudriavy volcano (Moyoro-dake in Japanese), which is younger than 2000 years only. Besides Kudrianvy, only Tukap volcano has active fumaroles.
Another vent of recent, but not historically observed activity is the Menshoi Brat lava dome inside the caldera.
Background:The caldera floor contains several lava domes, cinder cones and associated lava fields, and a small lake. The westernmost of the post-caldera cones, Menshoi Brat, is a large lava dome with flank scoria cones, one of which has produced a series of young (probably a few centuries old) lava flows up to 4.5 km long that reached Slavnoe Lake.
(Source: GVP / Smithsonian Medvezhia volcano information)
A small phreatic eruption occurred at Kudriavy volcano on 7 October 1999. It created a new crater 35 m deep and 30–40 m wide and destroyed parts of the summit lava dome. The eruption consisted in several explosions at intervals of 1-2 minutes and produced periodic ash emissions reaching up to ca. 100 m height. Blocks of 20-30 cm diameter were ejected up to 30-40 m. The new crater with vertical walls exposed incandescent hot areas of the interior of the lava dome.
The eruption was preceded by an unusually long dry period during which a large part of the Hot Lake (a rain-water fed lake near the lava dome) had almost dried out. An increase of ground temperature and increased seismic activity caused by changes in the hydrothermal system preceded the eruption and had been monitored since September.
Source: GVP / Smithsonian monthly reports
1992 intense fumarolic activity
Intense fumarolic activity was detected during fieldwork in late 1992. The maximum temperature at fumaroles at the lava dome of Kudriavy volcano was 910°C and rocks at 20-30 cm depth glowed red.
The last magmatic eruption of Kudriavy volcano was in 1883 and erupted basaltic andesite lava flows in the western crater. Even more than 116 years after the eruption, the temperatures of fumarolic gases exceeded 900 deg C.
Korzhinsky et al (2002), "Decade-long study of degassing at Kudriavy volcano, Iturup, Kurile Islands (1990–1999): Gas temperature and composition variations, and occurrence of 1999 phreatic eruption", Earth Planets Space, 54, pp 337–347