Glacial collapse behind Nepal’s ‘catastrophic’ floods
Nearly two-thirds of a high-altitude glacier near the Nepal-Tibet border sheared away and plunged about 1.2km into the Lhende Khola river catchment Wednesday. This triggered a chain reaction in which falling ice gathered rock, snow and sediment, temporarily blocked the river and then released a debris-laden torrent into the Bhote Koshi-Trishuli corridor, satellite analysis and scientists’ assessments showed.
Daniel Shugar, a geomorphologist at the University of Calgary, estimated from Planet Labs imagery that roughly 200 square metres of ice broke off at an altitude of around 5,200 metres and “collapsed about 1.2km vertically” to the valley floor. The drop “converted enormous gravitational energy into motion, allowing the mass to break apart and sweep up loose material rather than remaining a relatively coherent block of ice”. The collapse occurred on the Nepalese side of the border. The scale of the fall was crucial to what happened next.