Debris avalanches and the subsequent debris flow transformed from rock failure on the west face of Annapuruna IV, Nepal Himalayas

Abstract

Rock failure on the west face of Annapurana IV occurred on 5th May, 2012. Its scale is 500 m wide and 1200 m in relative height. The detritus fell down onto the glacier and crashed, blowing rock flour. Subsequently it turned into debris avalanches. The debris avalanches severely eroded the paleoglacial lake deposits. Then it included much fine materials and finally transformed into debris flow after jumping into the Seti gorge. The debris flow was also destructive enough to sweep away a small settlement, villagers and tourists who were happen to enjoy hot springs besides the river floor.