Abstract ID: 3.9887 | Accepted as Poster | Requested as: Poster | TBA | TBA

Abstract. Climate warming leads to intensive degradation of permafrost, expressed in the form of debris-ice massifs, which include moraine pedestals. The debris-ice mass of moraine pedestals fills the space between the lateral moraines, whose height reaches 50-70 m or more. The length of the moraine pedestals can reach 2 km or more, and the volume is several hundred million cubic meters. The formation of moraine pedestals as multilayer massifs occurred as a result of multiple glacier advances with deposits of rock avalanches and rockfalls on their surface. The presence of moraine partitions in the body of the pedestal limits the flow of meltwater from melting internal ice, and at a certain point in evolution, a significant mass of the pedestal becomes liquefied and rushes down in the form of high-density debris flows. The shear debris flow process continues for several days to ten or more, until the entire liquefied mass is carried down the valley. After the debris flow subsides, ravines remain in place of the moraine pedestals. The largest debris flow process occurred on the Sedongpu Glacier moraine pedestal in Southeastern Tibet in 2021. 335 million m3 of debris material was deposited in the Yarlung Zangbo River Valley. Before that, the glacier was torn off its pedestal in 2018 and a glacier mass of 130 million m3 was dumped down. Analysis of ravines on moraine massifs shows that some past debris flow disasters occurred as a result of similar processes, for example, the Issyk disaster in 1963 in Kazakhstan has signs of the formation of a ravine on the moraine pedestal of the Zharsai glacier, as well as the destruction of the Dzhailyk alpine camp in the valley of the Kullumkolsu river in 1983 in the Baksan river basin (Caucasus), the 2015 Barsem disaster in Tajikistan, and others. Timely identification of moraine pedestals unaffected by the debris flow process will make it possible to more realistically assess the scale of the debris flow hazard and avoid future disasters, including possible glacier detachments and associated debris flow processes.