A glacier let go above the Nepal-Tibet border on Wednesday morning, and within minutes a wall of meltwater and rock had erased whole villages, bridges and stretches of the only overland highway linking Kathmandu to Lhasa. By nightfall, Nepali officials had recovered 157 bodies and said the confirmed death toll had climbed past 160, with nearly 400 people, including 341 foreign nationals, still unaccounted for.

Geologists say an ice-rock avalanche broke away from a glacier and slammed into the Lhende Khola, a tributary of the Bhote Koshi River, damming it instantly. When the makeshift dam failed, water levels on the river reportedly surged roughly nine meters in half an hour, according to NPR's reporting from the scene. The surge scoured out the Rasuwagadhi border crossing, several hydropower and solar stations totaling roughly 430 megawatts of generating capacity, and long sections of road connecting Nepal to China.

A pilgrimage route turned death trap

The missing list reads like a snapshot of the Himalayas' peak trekking season: 142 Indian nationals, many reportedly on a Mount Kailash pilgrimage, plus dozens of Americans, Australians, Britons and Canadians, alongside Nepali police officers and South Korean hydropower workers caught mid-shift. Across the border in Tibet's Gyirong county, Chinese authorities have confirmed three deaths and 265 people missing, and a mudslide has cut roads, power and communications into the county's main port town, according to Al Jazeera's coverage of the disaster.

Locals and officials say there was almost no warning. Skies over the region had been largely dry, and the flood arrived without the heavy rainfall that typically precedes Himalayan flash floods, catching residents and travelers off guard. Reporters elsewhere are still racing to pin down exactly what triggered the collapse — a separate look at the disaster's cause and an earlier, lower casualty count shows just how fast the picture has shifted in the hours since the water hit.

"Please be patient. The government takes full responsibility for your rescue, treatment, food and shelter," Nepal's prime minister, Balendra Shah, told families of the missing.

Shah has convened Nepal's National Disaster Risk Reduction Authority and dispatched army helicopters, police and Red Cross teams to comb the Bhote Koshi gorge, the Trishuli and Narayani river systems, and the districts of Rasuwa, Nuwakot and Dhading, where the flood tore through. Kathmandu has formally asked both India and China for rescue assistance, and CNBC reports Indian Prime Minister Narendra Modi has pledged "all possible types of humanitarian assistance," while Bihar state in India began precautionary evacuations along the swollen river system downstream. Chinese President Xi Jinping has ordered an "all-out" search effort and called for stronger early-warning systems in the border region.

Scientists point to a familiar and worsening pattern: Himalayan glaciers are melting and destabilizing at an accelerating rate as the climate warms, feeding a growing string of glacial lake outburst floods across Nepal, Tibet and the wider region in recent years, including a smaller flood in the same area just last year.

For now, the search continues along riverbanks strewn with mud, crushed vehicles and the remains of homes, with rescue teams racing to find survivors before hope fades further. Nepal's tourism-dependent economy also faces a hard reckoning, with the Kathmandu-Tibet trade and pilgrimage corridor severed indefinitely and reconstruction of hydropower and road infrastructure expected to take months, if not longer.