Mass movements refer to the downward movement of rock and debris under the influence of gravity, without the intervention of geomorphic agents like water, wind, glaciers, or waves. These movements occur naturally due to gravitational forces.
Modes of Mass Movement
Mass movements can take different forms as they move downhill, including sliding, flowing, and heaving.
- Slide: In a sliding movement, the greatest movement occurs along the base of the mass. A distinct layer separates the unstable upper mass from the more stable lower mass, known as the shear plane.
- Flow: In flowing movement, material near the shear plane moves the fastest at the top, with the movement gradually slowing down deeper within the mass, reaching zero along the shear plane.
- Heave: This movement involves the shifting of particles, ranging from fine clay to large boulders, at a very slow pace.
Types of Mass Movements
| Mass Movement | Description |
|---|---|
| Solifluction | Occurs when water-saturated soil flows down a slope, often creating terrace-like formations. |
| Soil Creep | A slow, continuous movement of soil down a slope, driven by gravity. |
| Mudflow and EarthFlow | Mudflows occur on a large scale, while earth flows are localized movements of material down a slope. |
| Landslides | Rapid, sudden sliding of material, often triggered by heavy rainfall or earthquakes, typically found in areas with steep slopes. |
| Liquefaction | Earthquakes can cause clay-rich rocks to behave like plastic material, leading to liquefaction. |
| Avalanches | A sudden movement of snow, rock, ice, and soil down a mountain. |
Erosion and Deposition
- Erosion is the process by which earth materials are worn away and transported by natural forces like wind or water.
- Deposition occurs when these materials, carried by wind, water, ice, or sea, are laid down. This can involve sediments like pebbles, sand, mud, or dissolved salts in water.
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