Scientists Say a Glacier Caused the Nepal-Tibet Flood
Scientists say a broken glacier started the flood that killed at least 177 people.
A big flood happened on the Nepal-Tibet border.
At least 177 people died.
First, many people thought an earthquake caused it.
But scientists say a glacier fell down. This is called a glacial collapse.
The ice and rocks went into a river. The water rose very fast.
Rivers rose seven to nine metres in 30 minutes.
Scientists say the Himalayan ice is melting fast. They will study the glacier more.
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Collapsed Glacier Likely Caused Nepal-Tibet Flood, Scientists Say
First reports said an earthquake, but scientists now say part of a glacier fell into a valley.
Scientists have said that a collapsed glacier probably caused the flash flood on the Nepal-Tibet border. At least 177 people died in the disaster.
At first, many people believed that an earthquake caused a landslide, but the US Geological Survey later said that the cause was a "glacial collapse". This happens when a glacier, or part of a glacier, breaks apart. The glacier hit the bottom of a valley so hard that it registered a magnitude of 5.2.
Dr Simon Cook, a glacier expert at the University of Dundee, said his team found that the lower part of a glacier near the Langtang Lirung peak had collapsed. The peak is about 15km (9 miles) west of the flood site.
A large volume of ice and rock went into a small river, so the water in the rivers below rose by between seven and nine metres in only 30 minutes. Several water monitoring stations were washed away or damaged.
Scientists have warned for years about melting ice in the Himalayas. One study this year found that Hindu Kush Himalaya glaciers are losing ice twice as fast as before 2000.
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Scientists Point to Collapsed Glacier as Cause of Nepal-Tibet Floods
Preliminary investigations suggest that a glacier near Langtang Lirung broke apart, sending ice and rock into a river valley.
Preliminary investigations have pointed to a collapsed glacier as the cause of the flash flood on the Nepal-Tibet border, which has killed at least 177 people, scientists have told the BBC.
Initial reports of an earthquake led many people to believe that a tremor had caused a landslide. However, the US Geological Survey later clarified that the disaster was caused by a "glacial collapse", which is when a glacier or part of a glacier disintegrates. The impact of the glacier hitting the bottom of a valley was so powerful that it registered a magnitude of 5.2.
Dr Simon Cook, a glacier expert at the University of Dundee, said his team had detected that the lower part of a glacier near the Langtang Lirung peak, about 15km (9 miles) west of the flood site, had collapsed. An analysis by the International Centre for Integrated Mountain Development (ICIMOD) found there could have been an ice-rock avalanche from a high-altitude area. Ice and rock debris entered the Lende Khola, a tributary of the Bhote Koshi river, and water levels downstream rose by between seven and nine metres within 30 minutes. Several water monitoring stations were washed away or damaged.
Mike Searle, a professor of earth sciences at Oxford University, said the steep valleys around the mountain could have funnelled the water at higher speeds. He said the collapse of a whole glacier "in one go" was "very unusual". "These floods happen all the time, but not at this scale," he said.
It is still unclear what caused the glacier to collapse on Wednesday. An ICIMOD analysis released earlier this year found that Hindu Kush Himalaya glaciers are losing ice at double the rate since 2000. Dr Cook said similar events had happened in India, Switzerland and Italy in recent years.
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