Geological Hazards

• Geologic hazards


  Geologic conditions that present a risk to life (injury or death), of substantial loss or damage to property, or damage to the environment
• Landslide


  A variety of processes that result in the downward and outward movement of slope-forming materials, including rock, soil, artificial fill, or a combination of these
• Types of landslide movement

  • Falls
  • Topples
  • Slides
  • Flow
• Falls


  Landslides that involve the collapse of material from a cliff or steep slope
• Topples


  Topple failures involve the forward rotation and movement of a mass of rock, earth or debris out of a slope
• Slides


  A downslope movement of material that occurs along a distinctive rupture or slip surface
• Types of slides

  • Rotational slides (slumps)
  • Translational (planar) slides
• Rotational slides


  If the slip surface is listric (curved or spoon-shaped) the slide is said to be rotational
• Translational slides


  A downslope movement of material that occurs along a distinctive planar surface of weakness such as a fault, joint or bedding plane
• Types of flows

  • Debris flow
  • Debris avalanche
  • Mudflow
  • Creep
  • Earth flow
• Debris flow


  Involves the rapid downhill movement of loose earth material, usually with water
• Debris avalanche


  Similar to debris flow but has a faster flow
• Earthflow


  The earth material is finer and washed away leaving a depression bowl at the head
• A landslide may occur because the strength of the material is weakened
• Factors that can increase the chance of a landslide

  • Water
  • Erosion processes
  • Slope angle (steepness of slope)
  • Weathering processes
  • Volcanoes and earthquake activity nearby
  • Human activity
• Sinkhole

  A depression in the ground that has no natural external surface drainage
• Karst terrain


  Regions where the types of rock below the land surface can naturally be dissolved by groundwater circulating through them
• Types of sinkholes

  • Cover collapse sinkhole
  • Cover subsidence sinkhole
  • Dissolution sinkhole
• Flow

  Landslide that involve the movement of material down a slope in the form of a liquid
• Soluble rocks

  • Salt beds
  • Domes
  • Gypsum
  • Limestone
  • carbonated rocks
• Cover Collapse Sinkhole

  occur in the soil or other loose material overlying soluble bedrock
• Cover Subsidence Sinkhole

  It gradually grows where the sediment covers are permeable and contain sand
• Dissolution Sinkhole

  occurs in areas where calcareous is exposed on the ground or where thin layers of soil and permeable sand