A lake of water trapped behind a mass of glacial debris that buried a village and blocked a river in southern Switzerland this week has sparked fears of flooding in the Alpine valley, even as some water eased its way through the morass on Friday.

The landslide that buried a Swiss village and riverbed is refocusing attention on the role of global warming in glacier collapses around the world.

Permafrost is often called the glue that holds the mountains together. When it thaws, the mountains crumble, and they start to break apart. At the same time, the glaciers are shrinking and, as they do, they uncover mountainsides that are unstable without their thick coat of ice.