due to incessant rains, leading to the release of water in downstream areas.
It is one of the worst such disasters in the region in over 50 years.
This caused the rise of water levels in Teesta River that flooded at least four districts, including Mangan, Gangtok, Pakyong and Namchi.
Glacial lakes, like the South Lhonak Lake, are large bodies of water that sit in front of, on top of, or beneath a melting glacier.
As they grow larger, they become more dangerous because glacial lakes are mostly dammed by unstable ice or sediment composed of loose rock and debris.
In case the boundary around them breaks, huge amounts of water rush down the side of the mountains, which could cause flooding in the downstream areas.
This is called glacial lake outburst floods or GLOF.
GLOF can be triggered by several reasons, including earthquakes, extremely heavy rains and ice avalanches.