Multi-dynamic and multi-phase evolution of high-position avalanche hazards on the eastern margin of the Qinghai-Tibet Plateau

The eastern margin of the Qinghai-Tibet Plateau is an important active tectonic zone in the world, with steep slopes and frequent high-position avalanche hazards in the plateau canyon area. Combined with remote sensing interpretation, field investigation, borehole exploration and dating analysis, the multi-phase evolution characteristics of two high-position avalanches are studied in Luolong county and Yigong county, Tibet, China. The research results show that: (1) Most of the high-position avalanche hazards occurring along steep gullies are caused by complex factors, with the characteristics of alternating internal and external dynamic action; (2) The formation sequence of the deposits since the Late Pleistocene in the Chada gully, Luolong county, can be divided into four phases, which have respectively experienced the accumulation of moraines dominated by glaciation, the accumulation of high-position avalanche-debris flow triggered by paleo-earthquake, and the accumulation of ice-rock avalanche in the context of climate warming and the accumulation of recent gravity avalanche; (3) In the past 5,500 years, the Zhamu gulley in Yigong county has experienced more than 8 times large-scale avalanches. The dating results show that the giant avalanche event has a recurrence cycle on the order of hundreds years. Due to the different causes of giant avalanches in different stages, the recurrence cycle may be long, medium, or short; (4) In recent years, affected by global climate change, ice-rock avalanche hazards have occurred frequently, which may become the focus of research on high-position and long run-out geological hazards in plateau and canyon areas. The understanding of the multi-phase evolution process of high-position avalanche hazards in this paper has certain enlightenments for the prevention and mitigation of major geological hazards in the plateau canyon areas.