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• The Philippines


  • Located in an archipelago
  • Mountainous terrains
  • Often visited by typhoons which bring heavy rain
• The two conditions (mountainous terrains and typhoons) combined in the most unfavorable manner

  May cause landslides and sinkholes which are potential geologic hazards due to the topographic and geologic composition of land
• Landslides and sinkholes

  Soil collapsing downward, but they have different types and characteristics based on composition
• Geological hazards


  • Natural phenomena that cause major problems around the world
  • The expansion and development of cities has led to an increase in impact and damage due to geological hazards
  • Most are related to natural conditions, although some may be due to human activities
• Landslide


  Ground movement on a sloping terrain, does not happen on flat ground
• Landslides


  • Aggravated by rain because water is a natural agent for erosion
  • If rain or any source of water frequently flows down a sloping area, the gravitational descent of loosened soil makes it possible for landslide to occur
  • Structures built on steep-slope mountains have a high vulnerability to landslide hazards especially during heavy rains
  • Areas with steep slope, dense population and denuded terrain are distinguished by a high susceptibility to rainfall-induced landslide hazards
  • Long or regular rain may saturate the topsoil and the bedrock, weakening the soil base of buildings or structures
  • Without plants and trees whose roots can absorb water and hold the soil together, subsequent rain water can continue to loosen up the soil that anchors the buildings
  • A heavy downpour of rain can quickly destroy these buildings and communities, giving way to landslides, mudslides, or mudflows
• Types of Landslides


  • Soil Creep
  • Slumping Landslide
  • Debris Flow Landslide
  • Rock Fall Landslide
• Sinkhole


  A topographic depression created when groundwater dissolves the underlying limestone bedrock, often known as "sink" or "doline"
• Sinkholes


  • Occur in areas where the soil foundation is made of soft minerals and rocks such as limestone, salt beds, or any acidic rocks
  • The depth of sinkholes ranges from a couple of meters to several mile deep
• How sinkholes occur

  1. Water from rainfall seeps underneath the soil through cracks and fissures

  2. Water erodes the soil and forms a conduit system, increasing the size of these underground water systems as the soil is carried by the water through internal erosion

  3. This can either form a void filled with air with an underground drainage or a depression which then accumulates water and forms a pond

  4. Otherwise, it forms a hole once the cover collapses into the void which can be either filled with air or water
• Types of Sinkholes


  • Cover Collapse Sinkhole
  • Cover Subsidence Sinkhole
  • Dissolution Sinkhole
  • Artificial Sinkhole

  
• rockfall is a type of fast-moving landslide that happens when rock or earth falls, bounces, or rolls from a cliff or down a very steep slope.
• Slumping - a landslide consisting of a mass of material moving downslope as a unit, usually along a curved plane of failure. 
• Debris flows are geological phenomena in which water-laden masses of soil and fragmented rock rush down mountainsides, funnel into stream channels, entrain objects in their paths, and form thick, muddy deposits on valley floors.
• Soil Creep is the slow downslope movement of material under gravity. It generally occurs over large areas.
• Cover-collapse sinkholes or "dropouts" form where so much soil settles down into voids in the limestone that the ground surface collapses. The surface collapses may occur abruptly and cause catastrophic damages. 
• Cover-subsidence sinkholes form where voids in the underlying limestone allow more settling of the soil to create larger surface depressions
• dissolution sinkholes form where water dissolves limestone under a soil covering
• Over-pumping of groundwater, mining, and leaking pipes beneath roads and buildings are common causes of artificial sinkholes.