A recent study reported the high frequency of mass wasting events in the Sedongpu Gully of the Tibetan Plateau. This highlights significant geological and environmental changes that could have alarming consequences for India, particularly its Northeastern region. Read here to learn more about mass wasting.
Mass wasting is a natural process, but human activities, such as deforestation, mining, and construction, can increase their frequency and severity.
Understanding the causes and effects of mass wasting is essential for disaster preparedness and land-use planning, particularly in regions prone to these events.
Mass Wasting
Mass wasting, also known as mass movement, refers to the downward movement of soil, rock, and debris under the influence of gravity.
It encompasses a range of processes where earth materials move downslope, which can occur rapidly or gradually.
The main driving force behind mass wasting is gravity. Still, factors such as water saturation, slope angle, vegetation cover, and geological conditions can also influence the likelihood and severity of these events.
Types of Mass Wasting
Here are the primary types of mass wasting:
Falls
- Rockfalls: Rapid, free-falling movements where rock or debris breaks away from a steep slope or cliff. The material falls through the air and accumulates at the base of the hill.
- Talus Slopes: Accumulations of fallen rock debris that form at the base of cliffs or steep slopes.
Slides
- Slumps: Occur when a mass of earth material moves downslope along a concave-upward slip surface, causing the material to rotate and tilt backwards.
- Rockslides: Rapid movements of rock or debris along a well-defined surface, such as a bedding plane or a fault line. The material moves as a coherent mass.
Flows
- Mudflows: Fast-moving flows of water-saturated earth materials, often occurring in areas with little vegetation following heavy rains or volcanic eruptions.
- Debris Flows: Similar to mudflows but contain larger particles like rocks and boulders. These flows can be very destructive due to their speed and the large amount of material they carry.
- Earth flows: Slower, less fluid movements of soil and rock, typically occurring on gentle to moderate slopes. The movement is often continuous and can persist over long periods.
Creep
- Soil Creep: The slowest form of mass wasting, involving the gradual, almost imperceptible movement of soil and rock downhill. It can be caused by freeze-thaw cycles, wetting and drying, or the burrowing of animals.
- Solifluction: A type of creep that occurs in permafrost regions where the upper layer of soil thaws during the summer but remains saturated with water, causing it to slowly flow over the frozen ground beneath.
Avalanches
- Snow Avalanches: Rapid downhill flow of snow and ice, which can also include rock, soil, and vegetation. Snow avalanches are common in mountainous regions and can be triggered by various factors, including heavy snowfall, temperature changes, or human activities.
- Rock Avalanches: Extremely rapid movements of large volumes of rock, often triggered by earthquakes or volcanic activity.
Landslides
- Translational Slides: Movement occurs along a planar surface, such as a fault, joint, or bedding plane. The material moves parallel to the slope with little rotation.
- Rotational Slides: Characterized by movement along a curved surface, causing the sliding material to rotate and tilt backwards as it moves.
Topples
- Rock Topples: Forward rotation and overturning of rock masses out of the slope. This usually occurs when the centre of gravity of the rock mass extends beyond its base.
Lahars
- Volcanic Mudflows: These are fast-moving flows of volcanic ash, rock, and water that typically occur when volcanic activity melts snow and ice, mixing with loose volcanic material.
Causes of Mass Wasting
- Gravity: The primary force driving mass wasting.
- Water Saturation: Water adds weight to soil and rock, reducing friction and making it easier for materials to move downslope.
- Slope Angle: Steeper slopes are more prone to mass wasting due to the increased gravitational force.
- Vegetation: Roots can stabilize soil, reducing the likelihood of mass wasting; removal of vegetation increases risk.
- Earthquakes: Seismic activity can trigger landslides and other forms of mass wasting.
Effects of Mass Wasting
- Landscape Alteration: Mass wasting can drastically reshape landscapes, creating new landforms such as scarps and deposits of debris.
- Infrastructure Damage: Roads, buildings, and other infrastructure can be severely damaged or destroyed by mass wasting events.
- Hazards: Mass wasting can pose significant risks to human life, especially in areas where populations are located on or near unstable slopes.
Key Points from the Study in Sendongpu Gully
- Increased Mass Wasting Events: Mass wasting, which refers to the downhill movement of soil and rock due to gravity, has become increasingly frequent in the Sedongpu Gully area since 2017. This phenomenon is particularly concerning because it indicates significant geological instability in the region.
- Impact of Rapid Warming: The study emphasizes that the Tibetan Plateau, especially the Sedongpu Gully, has experienced a rapid increase in temperatures since 2012, with temperatures rarely exceeding 0ºC before this period.
- The warming has likely contributed to the increased occurrence of mass wasting events by weakening the structural integrity of the terrain, causing permafrost to thaw, and increasing the flow of water through the landscape, which exacerbates erosion and slope instability.
Potential Risks for India
The Tibetan Plateau is often referred to as the “Water Tower of Asia,” as it is the source of major rivers that flow into India and other South Asian countries.
- The increased frequency of mass wasting events could disrupt the flow of these rivers, leading to altered water availability and potential flooding downstream.
- For India’s Northeast, which is already prone to flooding, landslides, and other geological hazards, these changes could exacerbate existing vulnerabilities.
- The region’s infrastructure, agriculture, and settlements could face heightened risks due to the increased sediment and debris flow from upstream.
- India may need to strengthen its disaster preparedness and mitigation strategies, particularly in the Northeast, to address the potential impacts of these changes.
- This includes enhancing early warning systems for floods and landslides, improving infrastructure resilience, and collaborating with neighbouring countries on transboundary water management.
Broader Environmental Implications:
- The findings also underscore the broader impacts of climate change on fragile ecosystems like the Tibetan Plateau.
- The rapid warming and subsequent geological changes in this region could serve as a precursor to similar events in other mountainous regions worldwide.
Conclusion
The study on the Sedongpu Gully underscores the urgent need for a comprehensive understanding of climate change impacts on regional and global scales. For India, particularly the Northeast, this means preparing for potential disruptions in water resources and increased geological hazards.
Frequently Asked Questions (FAQs)
Q. Is mass wasting a landslide?
Ans: Landslides are a type of “mass wasting,” which denotes any down-slope movement of soil and rock under the direct influence of gravity. The term “landslide” encompasses five modes of slope movement: falls, topples, slides, spreads, and flows.
Q. What are weathering, erosion, and mass wasting?
Ans: Weathering is the physical disintegration or chemical alteration of rocks at or near the Earth’s surface. Erosion is the physical removal and transportation of weathered material by water, wind, ice, or gravity. Mass wasting is the transfer or movement of rock or soil downslope primarily by gravity.
Q. What are the two main sources of mass wasting?
Ans: Excessive precipitation is the most common trigger. Mass-wasting events are classified by their type of movement and material, and they share common morphological surface features.
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-Article by Swathi Satish
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