Glacier Hazards From Space

On August 4, 1985, Dig Tsho, a lake in the Mt. Everest region of Nepal, burst out, spilling an estimated 200 to 350 million cubic feet of icy water. The resulting flood wave, an astonishing 35 to 50 feet high, barreled down the valley for roughly 55 miles. Altogether, a $1.5 million hydropower installation, 14 bridges, and various trails and patches of cultivated land were destroyed. Such damages hit people in mountainous developing countries like Nepal especially hard. No land is available on the steep valley flanks for affected families to relocate to, and the destroyed infrastructure might have been the first step toward increasing the area's low standard of living. As is typical of many glacier floods, the outburst of Dig Tsho was triggered by an ice avalanche that crashed into the lake from an adjacent glacier. The resulting impact wave traveled to the moraine dam, overtopped it, and led to erosion of the dam, which finally broke.