LESSON 1 DRR

• Geological hazards


  Process or Phenomenon. Originates from the solid earth-geosphere.
• Landslides


  A downward movement of geological materials such as soil and rock.
• Landslides


  • Can be triggered by saturation of slope by extreme rainfall, or by vibration caused by earthquakes by human activity.
• Types of landslides

  • Creep
  • Slumps
  • Rockfall and topples
  • Mudslides
• Creep


  Generally slow, involve soil, and travel short distances.
• Slumps


  Can involve both soil and rock, travel short distances and vary from slow to very rapid.
• Rockfall and topples


  Involve rocks, are very to extremely rapid and can travel great distances.
• Mudslides


  Generally involve saturated soils moving at very to extremely rapid velocities and travel great distances.
• Effects of landslides


  • Cause property damage, injury, and death and adversely affect a variety of resources such as water supplies, fisheries, sewage disposal systems, forests, dams, and roadways.
• Negative economic effects of landslides

  • Loss of property value
  • Disruption of transportation routes
  • Medical costs in the event of injury
• Sinkholes


  Depressions or openings in the ground surface.
• Sinkholes


  Naturally occur in areas underlain by soluble carbonate or evaporite rocks like limestone, dolomite, gypsum, and salt.
• Types of sinkholes

  • Dissolution sinkholes
  • Cover-subsidence sinkholes
  • Cover-collapse sinkholes
• Dissolution sinkholes


  Aggressive dissolution occurs where flow is focused in pre-existing openings in the rock.
• Cover-subsidence sinkholes


  Tend to develop gradually where the covering sediments are permeable and contain sand.
• Cover-collapse sinkholes


  Tend to develop abruptly and cause catastrophic damages. They occur where the covering sediments contain significant amounts of clay.
• Karst terrain


  A type of topography that is formed by dissolution of bedrock in areas underlain by limestone, dolostone or gypsum. Such terrain has underground drainage systems that are reflected on the surface as sinkholes, springs, disappearing streams or even caves.
• Effects of sinkholes


  • Both natural and human caused sinkholes can pose a great risk to local communities. They can result in the partial and complete collapse of overground structures, cause damages to infrastructure, high economic losses, evacuation and displacement of residents and in some rare cases lead to the loss of lives. In nature, their impact is more limited to changes in the regional topography, change to local fauna and flora and change the course of subsurface water ways.