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Wednesday, December 08, 2021

Abrupt glacial direction shift in Kumaun Himalaya linked to tectonic activity, says study

Researchers explained that during the first advancement and subsequent retreat of the glacier, it left behind massive debris and moraine

Written by Anjali Marar | Pune |
Updated: November 25, 2021 6:40:21 am
Glacier, Kuthi Yankti river, Kali Ganga river, tectonic activities, Pithoragarh district, Uttarakhand, Uttarakhand news, Indian Express, India news, current affairs, Indian Express News Service, Express News Service, Express News, Indian Express India NewsKuthi Yankti river is a major tributary of the Kali Ganga river, that is supported by 88 glaciers spanning over 130 square km area and houses ice volume measuring about 9 cubic km.

Strong tectonic activities that occurred several thousands of centuries ago along a major tributary of Kali Ganga river in the present day Pithoragarh district of Uttarakhand could have led to an abrupt change in glacial flow direction.

A group of researchers from the Wadia Institute of Himalayan Geology, Dehradun, observed this truncation in the glacial flow direction along the valley of Kuthi Yankti river. They believe that it was sometime between the Last Glacial Maxima (24,000 to 19,000 years before present) and Holocene (10,000 years before present) that the glacier changed its course.

Kuthi Yankti river is a major tributary of the Kali Ganga river, that is supported by 88 glaciers spanning over 130 square km area and houses ice volume measuring about 9 cubic km.

In their recent study published in the Geosciences Journal, the experts have illustrated an unnamed glacier — 5 km in length and covering a 4 square km area — near Kuthi Yankti Valley in the Kumaun Himalaya. Originally set to glide towards the northeast, the glacier instead moved in the southeast direction, the researchers observed.

Structurally, the area lies above the Trans Himadri Detachment Fault and is known to be tectonically active. Using satellite and Google Earth images and toposheets, the group concluded that the glacier later merged with a neighbouring glacier named Sumzurkchanki.

“From the old geological maps, we noticed the presence of an active fault and thrust in the region that was dominated by sedimentary rocks. It has fragile topography along with active  tectonic activities,” Manish Mehta, glaciologist and lead author of the study, told The Indian Express on Wednesday.

As such, even today, faults and thrusts in the region continue to remain active, added Mehta. The region is vulnerable to avalanches and subjected to tectonic stresses.

While climate change may be one of the leading causes for the fast depletion of glacial extent and changing topography world over, in the Kumaun Himalayas, the bigger threat are tectonic activities.

The researchers explained that during the first advancement and subsequent retreat of the unnamed glacier, it left behind massive debris and moraine at its mouth. Overtime, this debris hardened. Later, when the glacier tried to advance further and cross this debris, it met strong opposition. Thus, the sheared rock wall was breached along the normal fault and changed the glacier’s flow direction, the study noted.

The study could pave the way for better understanding of glacial-tectonic inter-relations in a fragile region like the Himalayas.

In recent years, Uttarakhand has witnessed a number of disastrous calamities, such as extremely heavy rain triggering flash floods and landslides. In February this year, flash floods caused severe damage and killed several people in Joshimath area, and in Chamoli district.

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