Why it’s so hard to predict a tragedy like Nepal’s glacier collapse

On August 26, a mountainside near the Nepal-Tibet border gave way, sending seven billion cubic feet of ice and rock nearly a mile down into a river. The resulting flood tore through villages at speeds up to 100 miles per hour, killing more than 1,300 people, with thousands still missing. Scientists say disasters like this will become more common as climate change melts glaciers worldwide — the world has already lost about a fifth of its glacier mass in the last century, with at least another quarter expected to go by 2100.

As glaciers shrink, they leave slopes unstable in ways that are hard to foresee. Meltwater can seep into rock and weaken it, frozen soil called permafrost thaws and loses its grip, and glaciers themselves can dam up water that later bursts free. Some places have built systems to catch these risks early: Peru has drained dozens of dangerous glacial lakes, Switzerland evacuated a village just days before a glacier collapse, and Alaska closely monitors a glacier-dammed lake that floods yearly without casualties. But the Himalayas are vast and remote, with thousands of glaciers spread across the region, making constant monitoring nearly impossible.

Researchers are testing new tools that might help, including earthquake-style warning networks, fiber-optic cables that detect cracking ice, and a new U.S.-India satellite that recently picked up signs of ground movement on the Nepal slope weeks before it collapsed. Still, scientists warn there's no complete fix — as warming pushes more mountain regions past the freezing point, this kind of sudden, catastrophic collapse is likely to happen more often.