Context - A new study on the high frequency of mass wasting events in the Sedongpu Gully of the Tibetan Plateau since 2017 and the rapid warming of the area, which rarely experienced temperatures beyond 0º C before 2012, could be bad signs for India, specifically the country’s Northeast.
Key facts related to Sedongpu Gulley
- The Sedongpu Gully, in the catchment of the Sedongpu glacier and its valley, is 11 km long and covers 66.8 sq. km.
- It drains into the Yarlung Zangbo, or the Tsangpo River, near where it takes a sharp turn — called the Great Bend — while flowing around Mt. Namcha Barwa.
- This is one of the deepest gorges on the earth.
- The Great Bend is close to Tibet’s border with Arunachal Pradesh, where the Tsangpo flows as the Siang River.
- In Assam further downstream, the Siang meets the Dibang and Lohit to form the Brahmaputra, which flows as the Jamuna in Bangladesh.
Concept of Mass Movements
- Transfer the mass of rock debris down the slopes under the direct influence of gravity.
- Weathering is not a pre-requisite for mass movement though it aids mass movements. Mass movements are very active over weathered slopes rather than over unweathered materials.
- Air, water or ice do not carry debris with them from place to place but on the other hand the debris may carry with it air, water or ice.
- Mass movements are aided by gravity and no geomorphic agent like running water, glaciers, wind, waves and currents participate in the process of mass movements.
- Heave: heaving up of soils due to frost growth and other causes, flow and slide are the three forms of movements.
- Landslides are relatively rapid and perceptible movements. The materials involved are relatively dry.
- Slump is slipping of one or several units of rock debris with a backward rotation with respect to the slope over which the movement takes place.
- Debris slide is rapid rolling or sliding of earth debris without backward rotation of Mass.
- Debris fall is nearly a free fall of earth debris from a vertical or overhanging face.
- Rockslide is sliding of individual rock masses down bedding, joint or fault surfaces.
Solifluction is the flowage of water-saturated soil down a steep slope. Because permafrost is impermeable to water, soil overlying it may become oversaturated and slide downslope under the pull of gravity.