Glacial catastrophe of 20 September 2002 in North Osetia

The Geologic Structure of the Catastrophe Area

[11] The upper reaches of the Genaldon Ravine have a complex geologic structure. The close vicinity of the Kazbek Volcano caused the presence of effusive rocks, included stratigraphically into the Tsiklaur Formation (J _1-2 ) represented by siltstones and silty sandstones. The members of sedimentary and volcanic rocks compose the southwestern slope of the Shaukhokh anticline with a diorite body exposed in its core. In the area of the Kolka Glacier, diorite is exposed in the lower part of the left side of the Maili ice fall and in the lower part of the eastern Dzhimarai-Hoh wall, exposed by the glacier descent.

[12] The subvolcanic rocks are represented by the numerous diabase dikes feathering the Kazbek volcanic channel, known as the Kazbek Diabase Belt.

[13] Kazbek is not ranked as an extinct volcano. In the recent time the peak of its igneous activity is dated 280-180 thousand years ago. The next peak was recorded 50 thousand years ago. Its latest activity was dated 10,000 and 6000 years ago [Rogozhin et al., 2001].

Figure 8

[14] The neotectonic activity of the region at the present time is ranked as a fairly substantial one. The vertical crustal movements (VCM) attain the values of 0.7-0.9 mm year ^-1, which are the maximum values for the Caucasus region. These values were obtained by A. S. Teplyakova in terms of her dissertation work aimed to study the vertical crustal movements in the Gornaya Osetia region [Teplyakova, 1984]. It should be noted that the values of the vertical crustal movements decline abruptly in the northern direction from the Kazbek-Dzhimarai Massif. At the distance of 2-4 km this value declines to 0.4 mm year ^-1. It is possible that this significant change of the vertical crustal movements in the meridional direction controls the highly active collapsibility down the slopes of the Dzhimarai Massif, which is the main glacial area of the Kolka Glacier (Figure 8).

[15] The tectonic structure of the region proves the active geodynamic environment in the crustal block discussed. Numerous faults of different ranks cross the territory discussed, both in the least-west and north-south directions, causing upthrust and overthrust deformations.