What caused the deadly Nepal-Tibet floods? What is glacier collapse?

Two days after devastating floods caused by a glacier collapse along the Nepal-Tibet border, authorities are monitoring dangerous barrier lakes on both sides. On Nepal's side, a debris dam broke its banks, causing the Bhote Koshi river to rise and temporarily halting rescue flights. Across the border in China, a lake near Gyirong holding over 2.5 million cubic metres of water posed a high breach risk, though authorities said it was draining naturally. The disaster began when a massive section of glacier ice and rock collapsed into the Lende Khola river system, creating a natural dam that eventually gave way, sending a powerful surge of water, mud and rock downstream, destroying roads, bridges, and settlements.