What is glacial lake outburst flood? What happened in Uttarakhand's Chamoli?

Experts are uncertain about what caused the massive glacier burst at Chamoli in Uttarakhand on Sunday but the incident brought focus to the dangers of climate change the state is sitting on. In 2013, the state was devastated by a cloudburst which led to severe flood and landslides.

What is glacial lake outburst flood?

What happened at Chamoli is being seen as GLOF — a breach in a glacier which is not very unusual. When glaciers retreat, they leave a space which becomes a glacial lake being filled with water. When such a lake breaches, it is known as glacial lake outburst flood. It is yet to be investigated what triggered the breach — whether there was an avalanche in the area recently or whether the lake breach was the result of construction, anthropological activities, climate change etc.

Uttarakhand glacier burst: Day after tragedy, multi-agency rescue operations on

Sunday's deluge was believed to be caused by Nandadevi glacier breach. Nandadevi is the second highest mountain after Kanchenjunga.

What is an avalanche?

An avalanche is falling masses of snow and ice which gathers pace as it comes down the slope. But an avalanche is unlikely to result in the rise of water of that magnitude what Chamoli witnessed on Sunday.

Cloudburst

What happened in Uttarakhand in 2013 was a multi-day cloudburst. It is a sudden, very heavy rainfall accompanies by a thunderstorm. But it generally happens in monsoon.

In fact, the season in which such a disaster was witnessed has surprised experts as there is no immediate trigger that can be pointed to as the reason why water level rose to that level washing away two hydro projects.