Drrr (exam)

• Hazard


  Any dangerous situation or event that carries a threat to humans. Hazards can only be considered disasters once it affected humans.
• Types of Hazards


  • Natural Hazards
  • Quasi-natural Hazards
  • Technological (or man-made) Hazards
• Natural Hazards


  Arise from natural processes in the environment. e.g. earthquakes, tsunami, landslides, volcanic eruptions and floods
• Quasi-natural Hazards


  Arise through the interaction of natural processes and human activities. e.g. pollution, desertification, smog and fog
• Technological (or man-made) Hazards

  Arise directly as a result of human activities. Such as the toxicity of pesticides to agricultural lands, accidental leaks of chemical laboratories or radiation from nuclear plant.
• Geologic Hazard

  Extreme natural event in the crust of the earth that poses a threat to life & property
• Examples of Geologic Hazards

  • Earthquake
  • Volcanic Eruption
  • Tsunami
  • Floods
  • Fires
  • Typhoon
  • Landslide
  • Sinkhole

  
• Landslide


  The downslope movement of rocks, mud or debris under the influence of gravity
• Types of Landslide


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


  Very slow downslope movement of particles that occurs in every slope covered with loose, weathered Material
• Slumping


  Downward movement of rock debris, usually the consequence of removal of buttressing earth at the foot of a slope of unconsolidated material
• Debris Flow


  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
• Rock Fall


  Sudden slides caused by heavy rain the rock on the slope loosens and then slides down the slope
• Sinkhole


  A depression or cavity in the ground which is caused by water. It occurs in areas where the soil foundation is made of soft minerals and rocks such as limestone, salt beds, or any acidic rocks.
• Types of Sinkhole


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


  Develops suddenly (over an hour period) thus, causing catastrophic damage
• Cover Subsidence Sinkhole


  Gradually grows where the sediment covers are permeable and contain sand
• Dissolution Sinkhole


  Occur in areas where limestone is exposed at land surface or also is covered by thin layers of soil and permeable sand
• Artificial Sinkhole


  Caused by various human activities, such as groundwater pumping, drilling new water wells, construction activities and other development project
• Volcano


  A mountain or hill, having a crater or vent through which lava, rock fragments, hot vapor, and gas are being or have been erupted from the earth's crust

  
• Parts of a Volcano

  • The Crater
  • Magma Chamber
  • Conduit
  • Fumarole

  
• Crater


  Bowl-shaped depression at the top of the volcano that forms when the summit collapses after an eruption
• Magma Chamber


  Large underground cavity or reservoir where molten rock (magma) is stored before it erupts
• Conduit


  Long, narrow channel that connects the magma chamber to the surface of the volcano. Magma rises through the conduit and erupts
• Fumarole


  Vent on the surface of the volcano that emits steam, gas, and other materials. Fumaroles are found near the summit

  
• Types of Volcanoes


  • Shield Volcanoes
  • Composite Volcanoes (Stratovolcanoes)
  • Cinder Cones

  
• Shield Volcanoes


  Have a broad, gently sloping cone shape, similar to a warrior's shield laid on the ground. They are formed by numerous lava flows that spread out in all directions from a central vent. Shield volcanoes typically have non-explosive eruptions and produce thin, runny lava that flows for long distances.

  
• Composite Volcanoes (Stratovolcanoes)


  Tall, steep-sided volcanoes with a classic, cone-shaped appearance. They are formed by alternating layers of lava, ash, and other volcanic debris. Stratovolcanoes can have explosive or non-explosive eruptions and are known for their powerful explosions and pyroclastic flows.

  
• Cinder Cones


  Small, steep-sided volcanoes made up of loose, pyroclastic material such as ash, cinders, and volcanic bombs. They are usually formed by explosive eruptions that eject the material from a single vent, piling it up around the vent.

  
• Types of Volcanic Eruption

  • Vulcanian eruptions
  • Plinian eruptions
  • Pelean eruptions
  • Strombolian
  • Hawaiian eruptions
  • Icelandic eruptions

  
• Vulcanian eruptions


  Short, violent, relatively small explosion of viscous magma. This type of eruption may be repetitive and go on for days, months, or years, or they may precede even larger explosive eruptions.

  
• Plinian eruptions


  The largest and most violent of all the types of volcanic eruptions, they are characterized by the eruption of large amounts of ash, gas, and pumice into the air, forming a mushroom-shaped cloud that can rise several tens of kilometers into the atmosphere

  
• Pelean eruptions


  During a Pelean eruption, the volcanic vent can become blocked by viscous magma, causing a build-up of pressure that is released in a violent explosion. The resulting pyroclastic flow can move at extremely high speeds, reaching hundreds of kilometers per hour, and can be extremely destructive.

  
• Strombolian


  Distinct bursts of fluid lava. The explosions usually occur every few minutes at regular or irregular intervals. These eruptions are caused by the buildup of gas bubbles in the magma, which burst at the surface.
• Hawaiian eruptions


  Characterized by the effusive eruption of basaltic lava. The lava flows out of the volcano and spreads over a large area, forming shield volcanoes. These eruptions tend to be non-explosive, and the lava flows steadily and relatively slowly.

  
• Icelandic eruptions


  Typically non-explosive and relatively gentle compared to other types of volcanic eruptions, with lava flowing out of fissures or vents in the Earth's crust. The lava can flow over large distances, creating vast lava fields and shield volcanoes.

  
• Potential volcano-related hazards


  • Lava flows
  • Pyroclastic flows
  • Ballistic projectiles
  • Lahars
  • Landslides and other collapses
  • Volcanic earthquakes
  • Tsunamis
  • Volcanic gases
  • Tephra

  
• Lava (molten rock)


  Can erupt as fire fountains or lava flows (when it is runny) or as steep-sided domes (when it is viscous). Lava may destroy buildings and infrastructure, but it moves relatively slowly so is rarely a direct threat to people.
• Pyroclastic flows


  Hot avalanches of rock, ash, and gas that travel down volcano slopes at high speeds. They may be very dangerous close to a volcano.
• Ballistic projectiles


  Fragments of solid (blocks) or fluid (bombs) material ejected during the range of magmatic or phreatic (steam) explosive eruptions. Phreatic explosions are explosions caused by the interaction of water with hot rock or magma (lava).