Change in course of Himalayan glacier can help understand glacial-tectonic interaction

New Delhi, Nov 22 Indian researchers studying an unnamed glacier in one of the less explored regions in the upper Kali Ganga valley in Uttarakhand's Pithoragarh district have reported that the glacier had abruptly changed its main course, a first in the Himalayas.

"It is for the first time that such a change in course has been reported in a Himalayan glacier. The researchers have attributed this to the accumulated influence of both climate and tectonics," a release from the Department of Science and Technology under the Ministry of Science & Technology said.

A team of scientists from the Wadia Institute of Himalayan Geology (WIHG), Dehradun, an autonomous institute under the Department of Science & Technology, found that the unnamed North-east moving glacier had been abruptly truncated and forced to move towards South-east.

The abnormal behaviour of this unnamed glacier clearly suggests that not only is climate a controlling factor, but tectonics also play an important role in glacial catchments, the researchers said.

This example and the study becomes significant in view of the February first week disaster in Rishiganga valley, which was a latest example suggesting that the rock mass on which the glacier was sitting gradually became fragile (due to weathering, percolation of melt-water in joints, crevasses, freezing and thawing, snowfall, overloading, and gradually operating tectonic forces forcing rocks to mechanical disintegration) with due course of time and detached from the source rock.

"It clearly suggests that the Himalaya is an active mountain range and highly fragile where tectonics and climate play a critical role," the team of scientists said.

The study based on the tectonically sculptured unique glacier landform was published in the ‘Geoscience Journal'.

Based on remote sensing and an old survey map, the study assessed that the glacier had been affected by active fault and climate change. Tectonic activity and change in climatic conditions had changed the course and morphology of this glacier. An active fault produced a fault scarp that measures about 250 metre in height with a northerly dip. The fault trace is 6.2 km in length and trends towards NW-SE.

The WIHG team observed that the 5 km long unnamed glacier, which covered around 4 sq km area in Kuthi Yankti valley (a tributary of Kali river), has abruptly changed its main course. It moved, truncated, and ultimately merged with the adjacent glacier named Sumzurkchanki, as a result of tectonic forcing during the time between Last Glacial Maxima (19-24 ka) and Holocene.

It is one of the unique behaviors of the glacier, and no such observation has so far been reported on this type of glacier kinematics. The Last Glacial Maximum (LGM) occurred about 20,000 years ago while the Holocene is the current geological epoch, which began approximately 11,650 cal years before present.

The study indicates that climate is not the only factor that triggers disasters in the Himalayas, which is an active mountain range, but tectonics also play an important role in glacial catchments, the release said.

The study opens the doors for a new approach in glacier studies, particularly focused on the course change and evolution of new landforms formed by glacial-tectonic interplay, it added.

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