Geological Hazards

• Rainfall – Induced Landslide

  • A common occurrence in terrain with steep topography and soils that have degradable strength
• Rainfall – Induced Landslide

  • A kind of hazard that occurs in many places

  in the world; usually happens in mountainous

  places w/ a rainy environment
• Sinkhole

  • A depression in the ground that has no natural

  extent surface drainage (geologically)
• Sinkhole

  Commonly called “karst terrain” by

  geologists; regions where the type of rock

  below the land surface can naturally be

  dissolved by groundwater
• Soluble rocks include:

  ❖ Salt beds & Domes

  ❖ Gypsum

  ❖ Limestone

  ❖ Carbonate Rocks
• Causes of Sinkhole:

  • Mining
  • Over extraction of subsurface fluids like groundwater
  • Substantial weight of material on top of the ground that can trigger underground collapse of bedrocks
• Types of Sinkholes

  • Solution Sinkholes
  • Cover-collapse Sinkholes
  • Cover-subsidence Sinkholes
• Solution Sinkholes

  • Common in area where there is very thin soil cover
  • Water erodes the area gradually creating bowl-shaped depression
• Cover-collapse Sinkholes

  • It develops abruptly (over a period of hours) and can cause catastrophic damages
• Cover-subsidence Sinkholes

  • Are formed over a long period of time
  • This usually happens when sands mostly covers the bedrock
• Sinkholes are common in karts area but there

  are sinkholes that are formed because of

  human activity.
• Sinkholes are most likely occurred due to

  aquifer systems, however, groundwater

  pumping for water supply and irrigation may

  produce sinkholes.
• Sinkholes usually occur after heavy rains but

  it is important to note that droughts and

  freezes can also trigger the formation of

  sinkholes.
• It can be the cause of breakdown by the

  following: leaky faucets, destruction of

  sewerage, groundwater pumping and

  construction.