How a collapsing glacier may have unleashed the deadly Nepal-Tibet disaster

On August 27, a massive chunk of ice broke away from a glacier near the Nepal-Tibet border, causing a devastating disaster that claimed at least 180 lives. According to Simon Cox, a scientist at New Zealand’s GNS Science, the glacier collapse occurred at an altitude of approximately 5,200 meters and sent a massive debris flow down a canyon, picking up rocks, trees, and anything in its path.

The debris flow first struck a border post, as captured in harrowing CCTV footage, before traveling downstream into Nepal and flooding villages, demolishing bridges, and buildings. Seismic activity registered as a 5.2-magnitude earthquake, but further analysis determined it was actually caused by the glacier collapse.

Experts are using satellite imagery and on-site measurements to reconstruct the disaster, as the affected area is largely inaccessible. Lauren Vargo, a glaciologist at New Zealand’s Victoria University of Wellington, explained that by comparing before and after images, they can identify changes in the landscape that indicate what has been lost.

Soon after the seismic event, a nearby water monitoring station stopped transmitting, and downstream stations began going offline. In Kalikhola, near the Tibet border, water levels reached 12.3 meters by 2:14 pm local time. Early speculation suggested a glacial lake outburst flood (GLOF), but experts found no existing glacial lakes near the site of the collapse.

Instead, it is believed that the falling ice dammed the river, collecting water behind it, which was then released when the ice dislodged. The volume of water released was swelled by debris and mud carried downstream. Climatologist Lauren Vargo noted that while it is difficult to attribute any specific glacial event directly to climate change, the warming planet is a constant stressor on glaciers, creating disaster risks and reducing water availability for downstream communities.