Mass Movement

Mass Movement

1. Movement of regolith (rocks, mud, soil) downslope

2. Factors Influencing Mass Movement

   • Gradient
     • Steeper = faster + more likely
   • Water
     • Heavy rain = heavier regolith + lubricant
   • Vegetation
     • Roots slow down mass movement
   • Human Activity
     • Interfering with slopes (undercut) = steeper + more likely

3. Types of Mass Movement

   • Grouped according to speed + moisture
   • Soil Creep (Slow + Dry)
     • Slowest type (<1cm per yr)
     • Tilted poles, bent trees, broken fences, collapsed walls, terracettes, etc.
   • Landslides (Fast + Dry)
     • Material slides down an unstable slope
       • Heavy rainfall
     • Upland + coastal (+ undercut) areas
     • Sierra Leone (2017)
     • Very destructive
   • Mudflows (Fast + Wet)
     • Fastest type (several km)
     • Rock, earth, silt, peat, etc.
     • Bogburst
       • Peat + heavy rain = slurry
       • Very destructive + pollutes
       • Destroyed houses, roads, habitats, polluted rivers, etc.
       • Derrybrien, Galway (2003)
     • Lahar
       • Volcanic eruption + snowy mountain region
       • Mud, ash , hot water, etc.
       • Looks like concrete river
       • Nevado del Ruiz, Andes + Armero (1985)