Kolka Glacier and Genaldon River valley: yesterday, today, and

Abstract

The biggest glacial disaster in the Russian history took place on 20 September 2002 in the mountains of North Ossetia. A huge ice-rock-water mass rushed down the Genaldon River valley with a speed of 320 km/h from the Kolka Glacier. Having covered a distance of 18.5 km, it was stopped by the narrows of the Skalistyy Range and filled the Karmadon hollow with 120 million m³ of deposits. The material moved beyond the hollow as a debris flow, which went down the valley (10 km) devastating all the constructions in the riverbed. A total of 125 people were reported dead or missing. The glacier disaster of 2002 was unexpected, though such events had already occurred in 1834 and 1902. Slow sliding up to a distance of 4.5 km was noticed in 1960–1970 without any disastrous consequences. In 2002, two months before the disaster, a series of collapses from the Dzhimaraj-Hokh slopes (more than 4000 m high) on the backside of the glacier triggered the avalanche. The last ice-mass collapse had a volume of 10 million m³. As a result, the glacier hollow formed. The material from the glacier hollow was knocked out and went down the valley with the superficial moraine. The 100–150 m high water-ice-rock mass (with air also) was moving down the 400–500 m wide valley. The area covered from the collapse zone to the narrows was 12.7 km². The area of the ice-rock mass stopped by the “Karmadon Gates” was 2.1 km² (3.6 km long and 135–140 m wide with an average height of 60 m). The debris flow, which went down the narrows of the Skalistyy Range, covered an area of 2.5 km², and its total volume was about 9 million m³ with a thickness of 1 to 15 m. The flow on its way down the valley was also fed by the slope deposits and, to a greater extent, by the frontal masses of three huge ancient landslides on the left bank with a total volume of about 40 million m³. The high-energy flow undercut the toes of these landslides and displaced their material to a distance of 10–20 m. The 2002 Genaldon catastrophe is a natural phenomenon in a long chain of geological events. Such events have been repeated for many times since the last thousand years and will also be repeated in the future.