Sudden large-volume detachments of low-angle mountain glaciers – more frequent than thought?

Abstract. The detachment of large parts low-angle mountain glaciers resulting in massive ice–rock avalanches have so far been believed to be a unique type event, made known the global scientific community first for 2002 Kolka Glacier detachment, Caucasus Mountains, and then 2016 collapses two Aru range, Tibet. Since 2016, several so-far unrecognized glacier detachments recognized described, new ones occurred. In current contribution, we compile, compare, discuss 20 actual or suspected large-volume at 10 different sites Caucasus, Pamirs, Tibet, Altai, North American Cordillera, Southern Andes. Many reached volumes order 10–100 million m3. similarities differences between presented cases indicate that often involve coincidental combination factors related lowering basal friction, high increasing driving stresses, concentration shear stress, low resistance exceed stability thresholds. Particularly soft beds seem common condition among observed events as they offer smooth contact areas underlying substrate are prone till-strength weakening eventually failure under pore-water pressure. Partially fully thawed bed conditions presence liquid water could thus play an important role detachments. Surface slopes detached range around 10? 20?. This may enough enable development thick while also being steep allow critical stresses build up. We construct simple slab model estimate ranges slope width above which able detach when extensively losing resistance. From this all described study occurred due stress reduction more than 50 %. Most from particularly angle reach, down 5?, likely their ice content connected liquefaction potential, availability slurries, amounts water, well topographic setting typical glacial valleys. Low-angle combine elements physical processes surges break-offs glaciers. surge-like temporal evolution ahead geographic proximity other surge-type investigated can interpreted endmembers continuum instabilities. Though rare, appear frequent commonly thought disclose, despite local precursory evolutions, fundamental potential fail catastrophically.