Mass Wasting and Its Factors

Study Notes

Mass Wasting

Downslope movement of material due to gravity
Can result in loss of life and property damage
Occurs when gravitational force exceeds the slope's shear strength

Factors Contributing to Mass Wasting

Slope angle: Steeper slopes are more prone to mass wasting.
Weathering and climate: Weathering weakens materials, making them more susceptible to movement. Climate influences weathering processes.
Water content: Water can act as a lubricant, reducing friction and increasing the likelihood of movement. It can also add weight to the slope.
Overloading: Adding weight to a slope, such as through construction or accumulation of debris, can trigger mass wasting.
Removal of vegetation: Vegetation provides stability to slopes by anchoring soil and absorbing water. Removing vegetation increases the risk of mass wasting.

Classification of Mass Movements

Rate of movement: Rapid vs. slow
Type of movement: Falling, sliding, or flowing
Type of material: Rock, soil, or debris

Types of Mass Movements

Rockfalls: Free-fall of rocks, common in steep canyons and cliffs.
Slides:
- Slumps: Rotational slides along a curved surface, common in unconsolidated material.
- Rock slides: Movement on a more or less planar surface, involving solid rock.
Flows:
- Mudflows: Mostly clay and silt, containing up to 30% water. Common in arid and semi-arid environments.
- Debris flows: Larger particles than mudflows with less water.
- Earthflows: Slow, viscous movement of wet regolith.
- Quick clays: Liquefy spontaneously when disturbed, flowing like water.
- Solifluction: Slow movement of water-saturated material, common in areas with permafrost.
- Creep: Slow, imperceptible movement of soil or rock. Most widespread type of mass wasting.

Complex Movements

Combinations of different types of mass movements.
Often involve sliding and flowing.

Mass Wasting

Definition: Downslope movement of material under the influence of gravity.
Causes:
- Slope Angle: Steeper slopes are more susceptible to mass wasting.
- Weathering and Climate: Weathering weakens materials, making them more prone to failure. Climate influences water content and vegetation.
- Water Content: Excess water reduces friction between particles, leading to instability.
- Overloading: Adding weight to a slope can exceed its capacity.
- Removal of Vegetation: Roots help bind soil and prevent erosion.
Classification:
- Rate of Movement: Rapid (e.g., rockfalls, landslides) or Slow (e.g., creep, solifluction)
- Type of Movement: Falling, Sliding, or Flowing
- Type of Material: Rock, Soil, or Debris
Examples:
- Rockfalls: Freefall of rock, common in steep cliffs, canyons, and road cuts.
- Slides:
  - Slumps: Rotational slides along a curved surface, common in unconsolidated material.
  - Rock Slides: Movement along a planar surface, involving solid rock.
- Flows:
  - Mudflows: Fast-moving flows with high water content (up to 30%), common in arid and semiarid environments.
  - Debris Flows: Slower than mudflows, with larger particles and less water content.
  - Earthflows: Thick, viscous flows of wet regolith.
  - Quick Clays: Clay that liquefies and flows upon disturbance.
  - Solifluction: Slow movement of water-saturated material, common in permafrost areas.
- Creep: Imperceptible downslope movement, the slowest type of mass wasting.
- Complex Movements: Combinations of different types, often involving sliding and flowing.