THE disaster in Nepal on August 26 has made the question harder to ignore. A massive mass of ice and rock detached from a glacier near the Nepal-Tibet border and sent water, mud, boulders and debris through the Bhote Koshi and Trishuli river corridors. Villages were destroyed, bridges were swept away, and hydropower infrastructure was damaged. The broad lesson is clear: a disturbance high in the mountains can become a disaster far downstream. The Nepal event also matters because it was not a conventional glacial lake outburst flood. Initial descriptions varied, while later analysis pointed to an ice-rock avalanche or glacier collapse.