Glacial catastrophe of 20 September 2002 in North Osetia

The Glacier Body in the Karmadon Basin

[59] The ice that filled this basin changed substationally its appearance. The absolutely lifeless territory looked as the piling up of large dirty ice blocks covered by ash-color fine ice crumb. It was notably colder in the basin. During the first two months the ice grew more compact with its individual blocks being frozen together. The ground surface became notably lower, levelled and passable. The surface moraine began to form.

[60] The results of the topographic survey of the glacier avalanche (September 2002) were used to calculate its volume (115 million m ³ ) and area (2.1 km ² ). Because of its forced stopping the avalanche acquired the form of a lying wedge about 3.8 km long with the maximum thickness of about 160 m in the frontal part of the avalanche, and the width varying from 600 m to 900 m. During its retardation, the block material of the avalanche produced a significant promontary which filled the mouth of the right-side ravine damming the Kauridon small river. As to the Genaldon River, which lost its channel in the avalanche area, one week was enough for it to form a channel on the ice surface along the left side of the valley. In the lower part of the avalanche, the water flowed to its internal hollows and was thrown out into the canyon. All of the back-water pools that formed along the Genaldon River were of the flow-through type and disappeared very rapidly.

Figure 21

Figure 22

[61] The results of the topographic monitoring of the avalanche surface suggest the duration of the process of the avalanche disappearance. During the time period from the catastrophe which took place on 20 September 2002, to May 2003, the ice body lost 21% of its initial volume. During the time of 5.5 months (May-October) the ice lost another 18% of its initial volume, mainly as a result of its surface melting and the actively developing bottom thermal erosion restricted to the Genaldon and Kauridon river flows. As a result of these processes the area of the ice avalanche surface diminished by 0.4 km² and measured 1.7 km² now. The further changes in the ice volume are illustrated in Figure 21. Proceeding from the fact that the active melting phase in the region discussed lasts merely 4-5 months of a year, the complete degradation of the glacier body can be expected after a time interval of 5-6 years. In some areas the dead ice buried under the thick moraine cover may remain for a long time. The photograph presented in Figure 22 shows the ice avalanche barrier which existed in August 2005.