Look Out Below

For 10 days earlier this month residents in the tiny Italian Alpine village of Macugnaga (pop. 700) were under threat. A giant lake had formed atop a glacier on Monte Rosa, and authorities worried that the water would burst its banks — or worse, that the glacier itself would become dislodged, sending a river of ice, mud, rock and debris crashing down the mountainside and into Macugnaga situated below. Disaster was averted thanks to cooler temperatures and frantic efforts to pump water out of the lake.

But for Andreas Kääb, a glaciologist at the University of Zurich, the...