It is noteworthy that in the pictures, open parts of the banks of the lake are visible. This shows that after the release of water from the crack, the water level of the lake has continued to drop significantly and has caused severe flooding in the Teesta river basin downstream.
There is also evidence of landslides, which may have been a factor in the bursting of the lake shore.
Arup R Dasgupta, managing editor of Geospatial World (formerly GIS Development) magazine and a veteran ISRO imagery expert, said, “There is a lot of snow in the glacier these days and this snowpack may have exerted strong pressure on the mouth of the lake, causing the crack.”
South Lonak Lake is in North Sikkim at an altitude of 17,100 feet, not far from the India-China border.
The new photos show the exact area where the glacial lake breached. One of the photos indicates that water continued to flow from the lake on Friday, three days after the lake broke its banks.
Due to the decrease in the water level of the lake, a large area of its coastline has become visible. This is an area which was under water just three days ago.
Scientists of the Indian Space Research Organization (ISRO) had already said that the area covered by the lake has reduced by half. According to estimates, now only 60.3 hectares of its area has water.
The water in South Lonak Lake came from glacial runoff from the receding North Lonak Glacier and the Main Lonak Glacier. Leading scientist Dr SN Remya said in a 2013 paper that, due to this, the surface area of the lake increased by 500 meters and the average depth by 50 meters.
In the photographs taken in February this year, the lake is seen completely frozen, although the pattern of cracks on the surface of the ice is clearly visible.
However, Friday’s picture shows a large amount of broken ice and layers of floating ice on the surface of the lake. It is not clear whether this ice looks like this due to the increased flow of water towards the crack or this ice had melted to a great extent during the summer months.
Dasgupta said, “The first image shows a definite pattern of cracks on the surface of the lake ice, which indicates that the ice surface was under pressure, probably from the glacier. As seen in the second image, “This pressure probably increased due to fresh snow on the glacier. This could be the reason for the crack.”
An October 6 photo of South Lonak Lake shows clear evidence of a landslide on one of its banks. It is not clear whether the landslide caused the water to come out or was a factor that resulted in the breaching of the lake’s banks.
A study published in 2021 in the journal Geomorphology noted that, “Lake-terminating glaciers in Sikkim have seen rapid growth… South Lonak Glacier is no different. It is one of the fastest shrinking glaciers in The associated proglacial South Lonak Lake has become the largest and fastest growing lake in the state. This has raised concerns over the potential for danger as there is a large population in its downstream… ”