India, Aug. 28 -- A flash flood on the Nepal-Tibet border on Wednesday has killed close to 500 people and left more than 1,400 missing, making it the deadliest disaster in Nepal since the 2015 earthquake. Three days on, the toll continues to climb, a barrier lake formed by the flood's debris has begun overflowing, and rescue operations on both sides of the Nepal-China border have been halted.

High in the Bhote Koshi headwaters, close to the Langtang Lirung peak, a section of glacier covering about 0.2 sqkm broke off at roughly 5,200 metres of elevation and fell more than a kilometre onto the valley floor.

Later satellite images reviewed by geomorphologists Kristen Cook (Universite Grenoble Alpes) and Dan Shugar (University of Calgary) s...