Bezymianny - SpeedyLook encyclopedia

The Bezymianny is a Strato-volcan located in the peninsula of the Kamchatka, in Russia. Its name means in Russian " volcano without nom".

Localization

It belongs to the volcanos of the volcanic Group of the Klyuchevskaya Sopka, including/understanding several other volcanic buildings like Klyuchevskaya Sopka, the Sheveluch, the Ushkovsky, the Tolbachik and the Kamen). Bezymianny is included in the series of volcanos which constitute the Ceinture of fire of the Pacific. With broad to Kamchatka, a oceanic Pit 10.500 depth m and many seisms testify to the Subduction, at the speed of 10 cm/an, of the peaceful plate under the Eurasian plate; like all the volcanos of the Peninsula of Kamchatka, Bezymianny is thus a volcano of subduction.

Like the satellite image shows it (see the bond below), Bezymianny appeared on the sides of a volcano declared extinct, Kamen (4585 m), which is a close relation close to Klyuchevskaya Sopka (4835 m). It is obvious that with such a vicinity, Bezymianny (2882 m) appears to be of reduced size.

Structure of the volcano

Bezymianny is mainly made up of Andésite calcalcaline with potassium average rate. These andesites are generally rich in Augite and/or Hornblende. This volcano also produced andesitic Basalte and of a little Dacite.

A line of domes is aligned along the southern parts and west of the volcano. Some of these domes date from the period " pre-Bezymianny" ; the others are more recent. Its sides present several lava flows which, to the bottom of the slope, are covered with not cemented pyroclastic deposits.

The top of the volcano, an explosive crater formed by pulverization of the south-eastern side, in the horseshoe shape, has a dimension of 1,3 km X 2,8 km and 700 m of depth.

Eruptive activity

It seems that Bezymianny was formed on an old volcanic knob whose activity was attested end of the Pléistocène until the beginning of the Holocène. This " activity; pre-Bezymianny" was gone back to 11.000 to 6.900 years BPgrâce with ashes and pyroclastic elements present in the surrounding grounds (dating with ¹⁴C).

Formation of Bezymianny " moderne" began 4750 years BP, date on which the stratovolcano started to be formed and to separate by emissions of lava of the type andesitic Basalte or Andésite. After 2.000 years of sleep, the volcano again knew an activity into 3500 and 3300 BP.

Thanks to a dating of projections and ashes of this volcano by Téphrochronologie, by comparing them with ashes of the volcanos Sheveluch, Ksudach, and Khangar, one has been able to distinguish 3 principal phases in the activity from Bezymianny for 3.000 years:

B1 Phase: it took place between 2600 and 1700 years BP with a strong explosive activity and an emission of basalts and andesitic basalts.
B2 Phase: between 1400 and 1050 BP (600 to 950 after JC), the volcano knows a renewal of activity, with formations of domes, emission of lava but also of pyroclastic castings. At the end of this period, the volcano rises to 3100 m of altitude, and has a crater 500 m in diameter. Then he falls asleep for one long period.
B3 Phase: After a 1000 years sleep, Bezymianny is regarded as extinct. But on September 29th, 1955, the volcano awakes by a series of earth tremors (more than 1000 in three weeks). October 22nd, 1955, the eruption started with a moderate explosion which propelled a plume of ashes up to 8 km of altitude. Until December, it deposited a dust of gray ashes of fine Granulométrie to average on a radius of 60 km. The internal pressure made inflate the volcano, especially on the south-eastern side, so much so that one of the old domes of 100 Mr.
Le March 30th, 1956 towards 17:00 was raised, after several months of intense seismic activity, the south-eastern side is pulverized by a powerful side explosion (=blast). The top of the volcano, amputee of almost 250 m and to 0,5 km ³ of material then emitted a plume of ashes and Scorie S rising with nearly 40 km of altitude. The blast devastated the area on nearly 500 km ², laid down the trees at a distance of more than 20 km, burned the bark of those located between 20 and 30 km. There was a little later slag repercussion which, thereafter, caused pyroclastic castings sometimes very important (one of them followed the valley Sukhaya Khapista on a distance of 18 km), often prolonged by Lahar S. Heureusement, it be not victims in this uninhabited area. The side explosion, the disappearance of part of the top and the eruption plinienne which followed were extremely similar to those which knew the Holy Mont Helens with the the United States in 1980.
Depuis 1956, the eruptive activity is almost permanent (34 eruptions in 50 years). There is construction of domes of very pasty lava which, sometimes, are partly destroyed by more or less powerful explosions accompanied by pyroclastic flows and emissions of andesite with augite. This activity is accompanied by many fumerolles.

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