Landslides and Sinkholes

• Landslide


  Rock, dirt, or debris falling down a sloping section of land
• Landslides


  • Caused by storms, earthquakes, volcanoes or other factors which makes the slope unstable
• Major causes of landslides

  • Geology (material of the soil or rock, or layers of earth has weakened or stiffened)
  • Morphology (structure of the land, loss of vegetation or root system, prolonged rainfall or heavy water leakage)
  • Human activity (agriculture, construction, irrigation, deforestation, excavation)
• Rainfall-induced landslide


  Occurs due to prolonged or heavy rainfall, increasing the weight of the land mass
• The development of a rainfall-induced landslide may take several days but the landslide itself will only take a few minutes to cause a disaster
• Rainfall-induced landslides can form debris flows when they mix with additional water and sediments from their path
• Impending signs of a rainfall-induced landslide

  • Unusual noises (breaking trees, knocking boulders)
  • Slight rumbling sound that rises in amplitude
  • Rapid rise in water levels of the creeks, likely followed by increased turbidity
• Sinkhole


  A depression or hole caused by the collapse of the surface layer of the ground
• Sinkholes


  • Caused by the dissolution of soluble rocks such as limestone, dolomite, and gypsum
  • Can be natural or man-made (caused by drilling, mining, road construction, broken water or underground pipes)
• Types of sinkholes


  • Solution sinkholes (bedrock erodes, particles collect in spaces)
  • Cover subsidence sinkholes (bedrock covered by soil/materials not well-knitted, soil enters cracks and settles)
  • Cover collapse sinkholes (bedrock covered by deep soil, crack starts as bedrock erodes, weak points form in soil layers)
• Impending signs of a sinkhole

  • New cracks at the foundations of buildings and houses
  • Cracks in an area
  • Depressions at ground level
  • Rapid appearance of a crater in the ground