GYIRONG, Xizang, Aug. 28 (Xinhua) -- A massive mudslide that devastated the China-Nepal border region was triggered by a high-altitude glacier collapse on the Nepalese side, experts said, warning that such glacial disasters are becoming more frequent and severe amid global warming.
The mudslide struck Gyirong Port, a major China-Nepal land border crossing in southwest China's Xizang Autonomous Region, on Wednesday morning. As of 3 p.m. Friday, five people had been confirmed dead and 558 others remained missing, according to the latest official statistics.
According to Xinhua reporters at the scene, the silt layer in the core disaster area has reached a depth of over 1.5 meters, posing a high risk of entrapment and adding challenges to the rescue efforts.
THE TRIGGER: A GLACIER COLLAPSE
Satellite imagery and analysis by Chinese geological experts suggest that a high-altitude glacier collapsed in Nepal, triggering the devastating mudslide.
A comparison of satellite images showed that a glacier at an elevation of 5,200 to 5,400 meters had fractured and dragged rock debris along with it, forming a glacial debris flow, said Kang Shichang, director of the Institute of Mountain Hazards and Environment under the Chinese Academy of Sciences (CAS).
The event presents a classic disaster cascading effect, said Yao Tandong, an academician of the CAS and leader of China's second Qinghai-Tibet Plateau scientific expedition.
According to the experts, after the glacier collapsed, it was not just ice that came down. Vast amounts of ice and rock debris plunged down a mountain river channel, gathering mass and momentum as it moved downstream.
"The further downstream it traveled, the more destructive its force became and the more pronounced the secondary risks grew," Yao said.
"Precisely speaking, this is a chain disaster formed through continuous evolution from a high-altitude ice avalanche to a high-speed debris flow and a mudslide," said Guo Zhaocheng, an expert with China's Ministry of Natural Resources.
WHY THE IMPACT WAS SO SEVERE
Ouyang Chaojun, an expert on mountain hazards and engineering safety at the CAS, summarized three main factors behind the catastrophe: the initial ice-rock avalanche's massive scale and high elevation; its rapid transformation into a fluid debris flow that maintained high speed and depth; and the concentration of local population and buildings on flat riverbanks, leaving people directly exposed to the flow.
According to current assessments, it might have taken only about seven minutes between the onset of the ice avalanche and the mudslide hitting the port, said Guo. Such a narrow window highlights the difficulty of detecting and issuing early warnings for high-altitude, long-distance chain disasters.
Rescuers said the mudslide hurtled downhill at high speed, with no natural obstacles to dissipate its kinetic energy, unleashing massive destructive power when it hit the port.
Guo cited estimates showing that the ice-avalanche debris flow traveled at a speed of about 50 meters per second, an extreme velocity that left people with virtually no time to react.
As an important channel for China-Nepal border trade and a national first-class land port, Gyirong Port normally sees bustling commercial activity, a dense population and extensive infrastructure.
The disaster struck during daytime working hours, when crowds of people were present at the port, a factor rescuers said further raised the risk of casualties.
BEHIND IT: WARMING CLIMATE
Apart from the Antarctic and the Arctic, the Qinghai-Tibet Plateau and its surrounding areas are the world's largest glacier-covered region, known as the "Third Pole" of Earth.
Similar ice avalanches occurred on the plateau in 2016 and in India's mountain regions in 2021. According to scientists, against the backdrop of global warming, glacial disasters on the "Third Pole" and its surrounding areas are becoming more frequent, more widespread and more destructive.
Glaciers are sensitive to temperature rise. Human-caused climate warming has been the primary driver of the widespread glacial retreat observed globally since the 1990s.
Kang said that continued glacier melting will destabilize the glaciers themselves, make them more sensitive to external disturbances, and increase the frequency and intensify the severity of glacial disasters and their cascading hazard chains.
Therefore, reducing greenhouse gas emissions and curbing global warming are the core of long-term glacier conservation, Kang said. ■
