Geological Hazard

• Landslides may occur due to: 

  1. Steep slopes
  2. Weakening of slope materials
  3. Weathering of rocks
  4. Overloading of the slopes 
• Rainfall-Induced Landslide is a common occurrence in terrain with steep topography and soils that have degradable strength.
• There are five types of failures:

  1. Falling
  2. Toppling
  3. Sliding
  4. Spreading
  5. Flowing
• Sinkhole

  • a depression in the ground that has no natural external surface drainage
  • also known as a “wallet snake hole” and is a natural hole on the Earth's surface
  • geologists usually call it "Karst terrain"
• Karst Terrain is the region where the types of rock under the land can be easily dissolved by water
• Sinkholes are formed because of two processes:

  1. Dissolution. It is where both water and carbon dioxide are present in the environment, their varying levels affect the generation of carbonic acid.
  2. Suffusion. This is a phenomenon where pre-existing cavities underneath are covered by the sediments above.
• Soluble rocks are rocks that can be dissolved by a solvent (water). These include:

  • salt beds and domes
  • gypsum
  • limestone
  • carbonate rocks
• Types of sinkholes

  • Solution sinkholes - common in areas where there is very thin soil cover.
  • Cover-collapse sinkhole - develops abruptly and can cause catastrophic damages.
  • Cover-subsidence sinkholes formed over a long period of time and usually happens when sand mostly covers bedrock.