What Causes Glaciers to Collapse like the Event That Buried a Swiss Village?

An unstable glacier in the Swiss Alps collapsed this week, sending a deluge of rock, ice and mud through the valley below and burying the village of Blatten almost entirely. Scientists had warned about the possibility of a dangerous event related to the glacier, and village residents had been evacuated days earlier—but the glacier’s near-total breakup came as a surprise. One person is reported missing . Government officials initially estimated the debris deposit to be several dozen meters thick and approximately two kilometers long. Making matters worse, the collapse of the glacier, called the Birch Glacier, blocked the flow of the Lonza River, which runs through the valley. As a result, a newly created lake upstream from the debris field flooded an area that has now overflowed into t