geological hazard

• geological hazard - natural phenomena that cause major problems around the world
• landslide - the composition provided that there is an inclined terrain
• sinkholes - can occur on elevated or flat surfaces and can range from massive to barely noticeable which may leave a dent, a hole or a body of water on the ground
• color of signage meaning

  red - danger

  orange - warning

  yellow - caution

  blue - notice

  green - safety first
• red - the most visible color from a distance. The wavelength of light is able to penetrate further through fog, dust, and clouds, so you can see it even in the dark or on a misty day
• red - used for the highest level of danger
• yellow - makes humans' unconscious minds take notice in case of a sting
• yellow - combined with the feelings of danger it inspires make it perfect for the tier of danger below red.
• Yellow - there is a potential hazard
• blue - these aren't warning of imminent dangers, just giving instructions to ensure a safer journey
• blue - used for non-urgent instructions, as it is a neutral shade that will not lessen the impact of the more important red and yellow signs
• green - this is essentially the 'safe' colour
• landslide - ground movement on a sloping terrain. It does not happen on flat ground because of the angle on the ground, gravity induces the land to move downward
• types of landslide:

  1. soil creep landslide
  2. slumping landslide
  3. debris flow landslide
  4. rock fall landslide
• landslide can occur in areas with:

  1. steep slope
  2. dense population
  3. denuded terrain
• soil creep landslide - a very slow downslope movement of particles that occurs in every slope covered with loose, weathered material
• soil creep landslide

  
• slumping landslide - a downward movement of rock debris, usually the consequence of removal of buttressing earth at the foot of a slope of unconsolidated material
• slumping landslide

  
• debris flow landslide - happens when the slope becomes saturated with water, this then triggers a landslide of water-soaked mass of rock and soil that slides down the slope
• debris flow landslide

  
• rock fall landslide - sudden slides caused by heavy rain the rock on the slope loosens and then slides down the slope
• landslide mitigation and prevention

  1. removing populations from areas with a history of landslides
  2. restricting certain type of land use
  3. installing early warning systems
• methods of preventing landslide

  1. modifying slope geometry
  2. using chemical agent
  3. installing structures such as piles and retaining walls
  4. grounding rock joints and fissures
  5. diverting debris pathways
  6. rerouting surface and underwater drainage
• sinkhole - a topographic depression created when groundwater dissolves the underlying limestone bedrock
• sinkhole - all about water
• sinkhole - water dissolved minerals in the rock, leaving residue and open spaces within the rock
• sinkhole - water washes away the soil and residue from the voids in the rock
• sinkhole - lowering of groundwater levels can cause a loss of support for the soft material in the rock spaces that can lead to collapse
• sinkhole -  changing groundwater gradients
• sinkhole - - any changes to the hydrologic system (putting more water in or taking it out) causes the system to become at least temporarily unstable
• sinkhole - can result from seasonal changes in the groundwater table, freeze and thaw of the ground, and extremes in precipitation (drought vs heavy rain)
• Typical activities that can lead to sinkholes are:

  1. decline of water levels
  2. disturbance of the soil
  3. point-source of water
  4. concentration of water flow
  5. water impoundments
  6. heavy loads on the surface
• artificial processes - due to human activity, such as the collapse of abandoned mines and salt cavern storage in salt domes in places. They can also occur from the overpumping and extraction of groundwater and subsurface fluids.
• Natural processes - sinkholes may capture surface drainage from running/standing water, but may also form in high and dry places in specific locations. Sinkholes that capture drainage can hold it in large limestone caves. These caves may drain into tributaries of larger rivers.
• Sinkhole mitigation is mostly undertaken by regional and local governments. This can include continuous ground surveying using a range of techniques such as ground penetrating radar (GPR).
• Characteristics of sinkhole

  1. occurs in area where the soil foundation is made of soft minerals and rock
  2. depth of sinkholes ranged from couple of meters to several mile deep
• Types of Sinkhole:

  1. cover collapse sinkhole
  2. cover subsidence sinkhole
  3. dissolution sinkhole
  4. artificial sinkhole
• cover collapse sinkhole - it develops suddenly thus, causing catastrophic damage
• cover subsidence sinkhole - it gradually grows where the sediment covers are permeable and contain sand