More than 470 people have died and almost 1,000 are missing after a flood hit the border area between Nepal and Tibet. The disaster began on Wednesday when a glacier broke, causing a huge wave of water, ice, and rocks through Himalayan villages. Villages were destroyed, and roads and bridges were badly damaged, making rescue work very hard.

The main reason for the disaster was the melting and collapse of a glacier high in the mountains. This released water and debris, which moved quickly through the valleys and buried villages.

Now, a new, dangerous lake has formed near the Nepal-China border because flood debris blocked a river. Rescue teams worry that if this natural dam breaks, a second big flood could happen soon, so some operations have stopped to keep people safe.