About the ice-rock collapse from the northern slope of Mt. Dykhtau on August 12, 2023 and the potential threat of collapse from the slope of Mt. Dzhangitau (Cherek-Bezengiysky River basin, Central Caucasus)

Abstract

The causes and consequences of the ice-rock fall that occurred in 2023 on the Mount Dykhtau (Side ridge of the Greater Caucasus) are analyzed. This happened in the early morning of August 12, 2023 on the northern slope of Mt. Dykhtau (5.204.7 m a.s.l.) in the upper reaches of the Mizhirgi River valley of the Cherek Bezengiysky River basin at the altitude of about 4.400 m. The analysis of Sentinel-2 and Landsat-7 ETM+ satellite images of different times made possible to reveal the place where a block of ice had fallen from the hanging glacier, and to determine the area affected by this ice-rock block which volume was estimated as close to 0.9-1.0 million m3 and a distance of the runout about 2.3 km. As a result of the collapse, a group of tourists were injured, one of whom died. Investigation of the dynamics of the collapse site for the period 2015–2023 showed that earlier in the period September 3 – November 12, 2015 a crack formed on the same hanging glacier massif, which continued to grow until January 2016. This was followed by several ice-rock falls, the largest of which happened in the period April 10 – June 19, 2016. In total, all collapses of 2016 were comparable in volume to the collapse of 2023. By this time, the hanging glacier had been fully restored and occupied the same position it had in 2015. We next investigated a part of the slope of the Dzhangitau Zapadnaya mountain (5059 m a.s.l.) on the Bezengi Wall massif, on the hanging glacier of which the formation of a crack with a length of about 400 m was revealed in the summer of 2023. By September, the crack width had increased to 40 m. Leyer on, the crack became stable. But in the period of September ‒ December a certain surge of the glacier at the foot of Dzhangitau Zapadnaya mountain was revealed at a speed of about 1 m per day with the formation of a prominent frontal bank overlying the Bezengi Glacier. This research confirmed the activation of the landslide processes in the high-altitude zone and showed the need for continuous monitoring based on the analysis of satellite images for the timely revealing areas with a potential threat of any ice-rock falls and warning about the danger.