Mass Wasting and Its Factors

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.