After about four months of quiet, eruptions from Kliuchevskoi in January and February 2010 included days with vigorous plumes as high as 6-10 km; a cinder cone grew also inside the active crater. The previous eruption, which began on 8 October 2008 and continued until 16 April 2009, was characterized by Strombolian activity, large thermal anomalies detected in satellite images, lava flows on the NW flank, and phreatic bursts from lava contacting the Erman glacier (BGVN 34:03).

During mid-April to August 2009, the volcano was quiet and exhibiting weak fumarolic activity. Two eruptions followed, one in August and another in September 2009. Precursors to the 17 August eruption included elevated seismicity and ash visible in fumarolic emissions. The 17 August ash plume was small and rose to only ~5 km altitude.

During 11-18 September 2009 seismicity remained at background levels, although weak tremor was detected. Satellite imagery revealed a weak thermal anomaly over the volcano from 13 to 17 September. Strombolian activity that ejected tephra 70 m above the crater was seen at night on 16 and 17 September. On 18 September observers in Kliuchi (~35 km NNE) saw glow from the crater. Similar activity, including lava flows that began in mid-November 2009, continued in late September through February 2010 (table 13). A daytime photo on 12 November showed an E-slope lava flow with dense white clouds of condensed gases above it; a night photo on 13 November of the same area showed glow from the flow reflected in the gas plume.

Table 13. Summary of eruptive behavior at Kliuchevskoi during September 2009-February 2010. Courtesy of KVERT.

Seismicity, initially slightly above background levels in late September 2009 increased during the next month to include many earthquakes and weak to stronger tremor. Seismicity then remained above background levels for the rest of the reporting period.

Many Strombolian eruptions sent material well over the crater rim, and inside the crater they built a cinder cone. The tephra from these eruptions was ejected as high as 100 m above the crater initially in late September and early October, but then was ejected 200-300 m on average through much of the reporting period (table 13). Tephra rose 500 m above the crater at points during 16-22 October 2009 and during 24 December 2009-5 January 2010, but much higher plumes were reported by the Tokyo Volcanic Ash Advisory Center (VAAC) during early 2010. The longest plume reported occurred during 12-19 February 2010; it extended 243 km E. Lava flows remained active on the NW slope in January and February 2010 (figure 12).

Figure 12. Lava flows down the NW slope of Kliuchevskoi on 16 January (left, to 1.2 km) and 12 February 2010 (two flows, no distance given). Photos by Yuri Demyanchuk.

Lava flows first appeared on 14 November 2009 and traveled 500 m down the ESE flank. The flows continued to be active until early 2010. During 2-3 January 2010 a new lava flow descended the NW flank. Both the NW and the ESE flanks had active lava flows for a few days, until about 8 January at the latest, when the NW-flank lava flow became dominant. Notably, from 8 January through most if not all of February, phreatic explosions occurred at the front of the lava flow where it encountered ice and meltwater. The front was ~ 1.2 km down slope of its source by mid-January 2010.

Taller plumes. During 2009 and 2010 KVERT and the Tokyo Volcanic Ash Advisory Center (VAAC) noted some plumes up to ~ 5 km over the 4.8 km summit (i.e. plumes up to 10 km altitude). A brief mention of some representative plumes (both largely steam- and ash-bearing) follow. A gas-and-steam plume containing a small amount of ash seen during 5-9 December 2009. It rose to an altitude of 6.3 km and drifted E. During 12-14 January 2010 gas-and-steam plumes rose to an altitude of 6.8 km and drifted E. During 15-22 January, phreatic explosions from the lava-flow front ejected material that rose to altitudes of 4.5-8 km. Based on information from the Yelizovo Airport (UHPP) and satellite imagery, the Tokyo VAAC reported that during 18 and 22-23 January ash plumes rose to altitudes of 7-10 km and drifted N and NE. Ash fell in Kliuchi on 22 January. Gas-and-steam plumes rose to a maximum altitude of 6 km during 30-31 January and 8-10 February. Satellite imagery for the days 23 and 24 February 2010 revealed respective gas-and-steam plumes drifting 90 km NNW and 25 km ESE.

Seismicity. According to Gorelchik and Garbuzova (2001), seismologists identified earthquakes clustered in four regions at depth ranges of 4-5 km, 5-12 km, 12-20 km, and 20-40 km beneath the volcano. In the upper three regions seismologists noted primarily volcanic-tectonic earthquakes. These were presumably a result of a solid medium in those regions under the influence of continuously changing stress fields. Such fields are thought to be generated around subsurface pathways and features containing magma.

The deepest region, 20-40 km depths, generally corresponds to the lower horizons of the crust and transition into the mantle. At Kliuchevsoi, seismologists found this region to be an anomalous zone that generated many long-period earthquakes, events interpreted to result from magma migration. The diameter of the zone in the widest part was ~ 20 km and its center was shifted slightly NE of the crater. In some cases, earthquake foci migrated towards the surface starting from depths of ~ 25 km.

Reference. Gorelchik, V., and Garbuzova, V., 2001, Seismicity at Klyuchevskaya volcano as a reflection of it's modern igneous activity: Geodynamics and volcanism of the Kuril-Kamchatka island system (in Russian), IVGiG FEB RAS, Petropavlovsk-Kamchatsky.

Geological Summary. Klyuchevskoy (also spelled Kliuchevskoi) is Kamchatka's highest and most active volcano. Since its origin about 6000 years ago, the beautifully symmetrical, 4835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of sharp-peaked Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during the past roughly 3000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 m and 3600 m elevation. The morphology of the 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanology and Seismology (IV&S) Far East Division, Russian Academy of Sciences (FED RAS); Kamchatka Branch of the Geophysical Service of the Russian Academy of Sciences (KB GS RAS), Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs, http://www.emsd.ru/~ssl/monitoring/main.htm); Yuri Demyanchuk, IV&S FED RAS.