A catastrophic glacier collapse along the Nepal-Tibet border has triggered one of the deadliest natural disasters in the Himalayan region in recent memory, sending walls of mud, rock and water through mountain communities, destroying infrastructure and sweeping away tourists, pilgrims and local residents alike. [1]
What Happened — and Why
Early reports suggested an earthquake had triggered the disaster, but the US Geological Survey has since clarified that the event was caused by a "glacial collapse" — the disintegration of a glacier or part of one. [4] The force of the collapsed ice mass hitting the valley floor was so powerful it registered as a magnitude 5.2 seismic event, according to USGS data and scientists who analysed the event. [4]
Simon Cook, a senior lecturer in energy, environment and security at the University of Dundee who specialises in glaciology, told the BBC that his team had detected the collapse of the lower part of a glacier near Nepal's Langtang Lirung peak, approximately 15 kilometres west of the flood zone. [4] Cook said the glacier appeared to have collapsed in a north-westerly direction before travelling westwards downstream, and cautioned that "permafrost is partially holding some mountainsides together, this permafrost is warming and thawing and degrading so you are going to get more landslides." [4]
Mike Searle, professor of Earth sciences at Oxford University, offered a possible sequence of events: "I think the sheer wave of debris suggests there was a landslide first, the water built up, dammed the river, and then it burst in one huge great flood." [4] Scientists are now examining satellite imagery, recent rainfall data and evidence of glacial lake drainage to reconstruct the exact chain of events. [4] Cook noted that "climate change could have an impact," though scientists are still piecing together the precise causal sequence — a reminder that attribution analysis is ongoing, not settled. [4]
The Scale of Death and Disappearance
The human toll is still being counted, and figures have shifted rapidly as rescue teams reach previously inaccessible areas. Nepali police report at least 389 people killed. [4] Nepal's National Disaster Risk Reduction and Management Authority said on Thursday evening that 910 people remained missing in Nepal alone, including 517 foreign citizens, 44 members of the Nepal Army and 28 Nepal police officers. [4]
On the Chinese side of the border, CCTV reported that 558 people were missing in Tibet's Gyirong county, among them 260 foreign nationals, with the death toll there standing at three. [4] It remains unclear whether some individuals appear in both countries' missing-persons counts. [4]
Rescue teams found bodies approximately 100 kilometres downstream from the initial disaster zone, in Chitwan district, illustrating the enormous distance the floodwaters travelled. [1] Dozens of injured survivors have been airlifted to Kathmandu for advanced medical care. [1]
Tourists and Pilgrims Among the Missing
The disaster struck a region that draws visitors from around the world. Nepal's Tourism Board said 644 tourists remained missing as of Thursday, including 33 UK nationals — among them a 13-year-old girl and a 14-year-old boy. [4] Indian nationals account for the largest single group of missing foreigners, with 288 reported missing; 65 US tourists, 53 Ukrainians, 51 Malaysians, 39 Australians and 24 Canadians are also unaccounted for, along with smaller numbers from South Korea, South Africa, Portugal, the Netherlands and New Zealand. [4] China's foreign ministry separately said nearly 100 Chinese nationals are missing in Nepal. [4]
The Gyirong border crossing, the main transit point between China and Nepal, was among the sites engulfed. Footage showed a multi-storey building at the Rasuvagadhi border checkpoint consumed by a surging wall of mud and water along the Trishuli River. [4] Severe flooding has been reported along the Bhote Koshi, Trishuli and Narayani rivers. [4]
Rescue Operations Hampered by Destroyed Infrastructure
Search and rescue efforts face severe logistical obstacles. Nepali officials say dozens of bridges have been destroyed and nearly 40 kilometres of roads damaged, cutting off access to some of the worst-affected areas. [1] The Nepal Army has deployed helicopter operations that rescued more than 100 people on Thursday, including at least eight foreign nationals airlifted to Kathmandu. [1] Army teams also evacuated personnel trapped at facilities connected to the Trishuli hydropower project. [1]
Bishal Kumar Bhandari, chairperson of the Nepal Red Cross Society, said the focus has shifted from active rescue toward large-scale relief operations, with approximately 1,200 people displaced from at least three villages. [1] In Tibet, Chinese state broadcaster CCTV reported that a mudslide near the Gyirong land border crossing left surrounding areas buried under mud averaging more than 1.5 metres deep, with some road sections covered by more than 2 metres. [1]
Risk of Secondary Flooding
Authorities are warning the disaster may not be over. The International Centre for Integrated Mountain Development (ICIMOD) has cautioned that secondary flooding could occur in the coming days as debris washed into river systems. [4] ICIMOD said it is assessing whether the Trishuli River has been temporarily blocked in narrow sections — a scenario that could produce a landslide dam and trigger a second catastrophic flood event. [4] A lake of rising water has already formed at a site along the China-Nepal border, prompting fears it could breach its banks. [4]
International Response
Nepal's Prime Minister Balendra Shah described the nation as "shocked and deeply distressed" and said officials would coordinate with China on the response. [4] Chinese President Xi Jinping called for an "all-out" search effort and pledged stronger monitoring and early warning systems. [4] Indian Prime Minister Narendra Modi said his government was "prepared to provide Nepal with all possible types of humanitarian assistance." [4]
The United States has committed $500,000 in emergency aid to cover shelter, water, sanitation and relief supplies. [4] UK Prime Minister Andy Burnham announced £5 million in support for the Nepalese government, saying the UK would do "everything we can" to assist British nationals. [4] UN Secretary-General António Guterres said he was "saddened by the severe flooding" and that UN teams were mobilising supplies and personnel. [4]
What to Watch Next
The coming days will be critical on multiple fronts: whether the water body forming along the border holds or bursts; whether rescue teams can reach communities still cut off by destroyed roads and bridges; and whether the death and missing-persons tolls continue to climb as more areas become accessible. Scientists will also be watching satellite data closely for signs of further glacial instability in a region where climate-driven glacier retreat is accelerating — and where the risk of similar events is, by most expert assessments, growing.