Himalayan glacier changed track 20,000 years ago: study

Scientists say it fused into an adjacent glacier in present-day Pittoragarh.

November 23, 2021 09:21 pm | Updated November 26, 2021 08:22 am IST - NEW DELHI

Fresh activity: The glacier was large enough that it formed its own “valley”.

Fresh activity: The glacier was large enough that it formed its own “valley”.

Nearly 20,000 years ago, a 5-km-long Himalayan glacier “abruptly” changed course and over time fused into an adjacent glacier in present day Pittoragarh, Uttarakhand. This is the first time, say scientists who have described the findings in a peer-reviewed journal this week, that such a turn in glacier’s course has been recorded in the Himalayas. Change in climate along with tectonic movement probably caused this to happen.

Based on remote sensing and an old survey map, the study, which appears in the Journal of Geosciences, assessed that the glacier had been affected by active fault and climate change.

The glacier, which does not have a name and lies in an extremely inaccessible region, was large enough that it formed its own “valley” and the accumulated debris that accompanies the formation of glaciers probably caused it to turn from a north-eastern direction to a south-eastern course, said Manish Mehta of the Wadia Institute of Himalayan Geology (WIHG), a Department of Science and Technology institute, who is among the authors of the study.

The study adds to evidence of the inherent instability of the Himalayan region, among the youngest mountain ranges in the world due to which the underlying tectonic plates that support it are not stable but are jittery and frequently trigger earthquakes and landslides.

The event had “similarities” to the February disaster in Rishiganga valley, Uttarakhand, in which a large mass of rock and debris detached from a glacier and hurtled down the Rishiganga river. In the process two hydropower dams were destroyed and at least 200 were either killed or went missing in Chamoli, Uttarakhand.

“This event that we have described is a much larger event than what happened in February. However, that the Himalayan region is ecologically fragile and prone to events such as these is certain,” Mr. Mehta added.

The WIHG team observed that the 5-km-long unnamed glacier, which covered around 4 sq km in Kuthi Yankti valley (Tributary of Kali River), after changing course moved and ultimately merged with the adjacent glacier named Sumzurkchanki as a result of tectonic forcing during the time between Last Glacial Maxima (19-24,000 years ago) and Holocene (10,000 years ago).

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