Dikii Greben'

51°27’ N, 156°59’ E, summit elev. 1079 m

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Dikii Greben' volcano (Figs.1-3) is located in South Kamchatka, immediately west of the Kurile Lake caldera. This Holocene eruptive center consists of a main lava dome (Mt. Nepriyatnaya - "Unpleasant") and a number of flank domes, occupying with their lava and pyroclastic flows an area of more than 60 km². Dikii Greben' is the largest Holocene extrusive edifice in the Kurile-Kamchatka island arc. It is composed of silicic rocks (Hb-bearing moderate-K dacite-rhyolite) (Bindeman and bailey, 1994).

Geological and tephrochronological studies suggest that Dikii Greben' massif was formed during three short stages of activity separated by ~3000-yrs long repose periods. The volcano came into existence immediately after the Kurile Lake caldera collapse about 7600 ¹⁴C yrs BP. However, its magma differs in composition from that of caldera and intra-caldera eruptions. The second phase of activity took place roughly 4500 ¹⁴C yrs BP. The largest part of Dikii Greben' edifice, including profuse lava bodies, descending to the north and south from Mt. Nepriyatnaya, formed about 1600 ¹⁴C yrs BP. Conspicuous crustal deformations and landslides ocurred duirng all the three stages; some of the landslides dammed Ozernaia river (Fig. 2), which flows from the Kurile Lake.

Dikii Greben' eruptive history suggests that it is repeatedly resuming its activity and, therefore, it may be regarded as a potentially active volcano.

The most recent eruption produced a tephra-fall deposit, several lava domes and a >350 m thick, 4 km long southern lava flow with well-expressed marginal levées and arcuate pressure ridges, fairly typical example of a coulée. In addition, east and north of the main dome, two large lava bodies were formed, whose features are better explained as origintaing from sector collapse of the dome(s) (Fig. 3). The eastern body consists mostly of huge dome chunks, forming specific steps towards the Kurile Lake and stopped by an older dome (Fig. 2). The northern lava body is ~8 km long and >200 m thick with a volume of 4-5 km³. It resembles viscous blocky lava flow with marginal levées and ~50 m high ogive-like ridges, but unlike those in a regular lava flow, these are arcuate against the direction of motion (Fig. 3).The most distal part of the deposit exhibits hummocky topography typical of debris avalanche deposits. We suggest a collapse origin for both northern and eastern lava bodies (Ponomareva et al., 2006). 

Literature

Bindeman IN, Bailey JC (1994) A model of reverse differentiation at Dikii Greben' volcano, Kamchatka: progressive basic magma vesiculation in a silicic magma chamber. Contrib Mineral Petrol 117: 263-278

Braitseva OA, Melekestsev IV, Ponomareva VV, Sulerzhitsky LD (1995) The ages of calderas, large explosive    craters and active volcanoes in the Kuril-Kamchatka region, Russia. Bull Volcanol 57 (6): 383-402

Ponomareva VV, Dirksen OV, Sulerzhitsky LD (1995) Eruptive history of Dikiy Greben volcano - the largest Holocene extrusive edifice in Kamchatka, Russia. Abstracts of the International Workshop on Volcanoes Commemorating the 50th Anniversary of Mt.Showa-Shinzan, p.159

Ponomareva VV, Melekestsev IV, and Dirksen OV (2006) Sector collapses and large landslides on late Pleistocene-Holocene volcanoes in Kamchatka, Russia. J Volcanol Geotherm Res (in press)