Frequent mass wasting in Tibet a cause for worry in India
- August 26, 2024
- Posted by: OptimizeIAS Team
- Category: DPN Topics
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Frequent mass wasting in Tibet a cause for worry in India
Sub: Geo
Sec: Indian Physical geo
Context:
- Mass wasting has increased in the Sedongpu Gully, Tibetan Plateau, since 2017 due to rapid warming.
- A geological event, mass wasting is the gravity-influenced movement of rock and soil down a slope.
- A gully is a landform created by erosion from running water, mass movement or both.
Sedongpu glacier:
- 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 (altitude 7,782 metres) and Mt. Gyala Peri (7,294 metres) to create a gorge 505 km long and 6,009 metres deep. 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.
River Choking and Flash Floods:
- China plans to set up a 60-gigawatt project on the Tsangpo, which will [have] thrice the capacity of the Three Gorges project on the Yangtze, the world’s largest hydropower plant, raising concerns about river choking and flash floods in downstream areas.
- The Brahmaputra, one of the most sediment-laden rivers, already carries over 800 tonnes of sediment at Pandu in Guwahati, increasing to more than a billion tonnes in Bangladesh.
- Increased sedimentation could worsen flood hazards, cause river channels to choke, and affect livelihoods dependent on fishing.
- More than 700 million cubic metres of debris have been mobilised since 2017 due to warming and earthquakes.
Patterns of Landslides:
- The Sedongpu study analysed 149 satellite images from 1969 to 2023, identifying 19 large mass-wasting events in the gully.
- These events were categorized into ice-rock avalanches (IRA), ice-moraine avalanches (IMA), and glacier debris flows (GDF).
- Debris from IRAs has temporarily blocked the Tsangpo River, leading to catastrophic flash floods downstream, such as those in Arunachal Pradesh and Assam in 2000.
Lull Before Hyperactivity:
- The gully experienced its first mass wasting event from 1974 to 1975, with no catastrophic events until 1987.
- A significant increase in mass wasting events has been observed since 2017, with 13 out of 19 events occurring post-2017, accounting for 68.4% of the total.
- The study notes that the area’s bedrock is mainly Proterozoic marble, with land surface temperatures rarely exceeding 0º C before 2012, but increasing rapidly since then.
Mass Wasting:
- Mass wasting, or mass movement, involves the movement of rock or soil down slopes under the force of gravity.
- It differs from other erosion processes as the debris is not transported by a moving medium like water, wind, or ice.
- Types of mass wasting include creep, solifluction, rockfalls, debris flows, and landslides, each with unique characteristics and varying timescales, from seconds to hundreds of years.
- This process occurs on terrestrial and submarine slopes and has been observed on Earth and other bodies in the Solar System, including Mars, Venus, and Jupiter’s moon Io.
Source: TH