Tsunami at 17,000 Feet struck Himalayan valley and towns below

A glacial lake at South Lhonak collapsed on Oct. 3, 2023, sending a rapid outburst flood down the Teesta River that Indian authorities say killed more than 100 people; experts had installed a weather station at the lake less than three weeks earlier.

A glacial lake high above the Teesta River at South Lhonak collapsed on the night of Oct. 3, 2023, sending a rapid outburst flood downvalley. Indian authorities reported more than 100 deaths and substantial damage in low-lying towns such as Rangpo Forest. Scientists note the lake had grown as the glacier retreated and that moraines — the natural dams of frozen earth and rock — can become unstable as temperatures warm. Disaster experts had installed a weather monitoring station at the lake less than three weeks before the collapse. Key facts: - Date and location: South Lhonak Lake collapse on Oct. 3, 2023, releasing water into the Teesta River. - Human toll: Indian authorities reported more than 100 people dead and many bodies unidentifiable. - Monitoring and warning: Indian and Swiss teams had begun placing monitoring equipment days earlier, and an alert from border police helped prevent additional losses, officials said. - Cause and mechanics: Scientists describe such events as moraine failures tied to glacier retreat and lake growth, producing sudden floods that carry large amounts of water and debris downstream. Summary: Officials have described the incident as a rapid glacial lake outburst from South Lhonak that sent a destructive flood through the Teesta valley. Authorities report more than 100 deaths and recovery and assessment work is ongoing. Undetermined at this time.