A glacial collapse occurs when a large mass of ice and rock suddenly breaks from a mountain slope, potentially triggering avalanches, debris flows and flash floods. The Nepal-Tibet disaster shows how such cascading Himalayan hazards can travel vast distances and overwhelm conventional early-warning systems.

NEW DELHI — A deadly flash flood near Nepal's border with Tibet on Wednesday may have been triggered when the lower part of a glacier broke off and...

The deadly flash floods that tore through Nepal’s Himalayan border region on Wednesday may have been triggered by a massive chunk of glacier breaking away high in the mountains…