BANGKOK: Indian rescuers are searching for over 100 people missing in a flash flood caused by a glacial lake bursting its banks, a risk scientists warn is increasing with climate change.
AFP explains what glacial lake outburst floods are and the risks they pose, particularly in parts of Asia:
WHAT IS A GLACIAL LAKE OUTBURST FLOOD?
A glacial lake outburst flood (GLOF) is the sudden release of water that has collected in former glacier beds.
These lakes are formed by the retreat of glaciers, a naturally occurring phenomenon that has been turbocharged by the warmer temperatures of human-caused climate change.
Glacier melt is often channelled into rivers, but ice or the build-up of debris can form what is effectively a natural dam, behind which a glacial lake builds.
If these natural dams are breached, large quantities of water can be released suddenly from the lakes, causing devastating flooding.
WHAT CAUSES THESE BREACHES?
The natural dams holding back glacial lakes can be breached for a variety of reasons, explained Lauren Vargo, a glacier expert and scientist at the Antarctic Research Centre in New Zealand.
Causes include “an avalanche of snow, or a landslide causing a wave in the lake, or overfilling of the lake … from rain or the glacier melting”, she told AFP.
Sometimes the dam has been gradually degraded over time or is ruptured by an event like an earthquake.
The breaches are highly unpredictable, “because they can be caused by so many different factors”, she added.