UNDERSTANDING THIS DISASTER
On the morning of Aug 26, scientists found that a mass of bedrock and overlying glacial ice broke off Langtang-Lirung mountain and plunged from a height of about 5,200 m more than 2 km down to the valley floor.
It resulted in a ground impact significant enough for the United States Geological Survey to report a 5.2 magnitude earthquake.
A rush of melting ice, rock and debris entered the high altitude Lhende Khola river in Tibet, from where a large lake briefly formed before breaking and surging downstream, carrying all in its path.
Research is continuing into the exact mechanics of this particular failure, but scientists believe the mountain may have been weakened by a combination of long-term geological processes and a warming climate.
As glaciers and snow retreat, more rock is exposed to heat, while warming can degrade the permafrost that helps bind high mountain slopes together, Azam said.
Bolch has spent years studying glaciers across the Hindu Kush Himalaya. As they have retreated, he has observed some pulling back from valley floors towards steeper mountain slopes.
In areas of permafrost, ice can be frozen firmly to the rock beneath it. As temperatures rise, that bond can weaken, while meltwater seeping into cracks can further destabilise the glacier, Bolch said.
“This is for sure an impact of the changing climate and the increased temperatures. It’s hard to predict, but I’m pretty sure we will see something similar happening in the next couple of years around the world,” he said.
While scientists can observe glacier surfaces, they know little about what is happening at the glacier bed or internally, including the subtle processes that might precede this kind of failure, Shrestha said.
“There are several hidden stories and hidden signs,” he said of the unseen interior and bottom of glaciers.
“These are the things that we need to know better to anticipate these kinds of disasters in future.”
