Untitled

• Volcanic Hazard


  The probability that a volcanic eruption or related geophysical event will occur in a given geographic area and within a specified window of time
• Volcanic Eruptions are one of the Earth's most dramatic and violent agents of change
• Volcanoes


  • Exhibit precursory unrest that if detected and analyzed in time allow eruptions to be anticipated and communities at risk to be forewarned with reliable information in sufficient time to implement response plans and mitigation measures
• Potential volcano-related hazards


  • Pyroclastic density currents
  • Lahars
  • Ash fall
  • Lava flows
  • Tephra fall and ballistic projectiles
  • Volcanic gasses
• Pyroclastic density currents


  Gravity-driven, rapidly moving, ground-hugging mixtures of rock fragments and hot gases
• Pyroclastic density currents


  • Forms a dense fluid that moves along the ground with an upper part that is less dense as particles fall toward the ground
• Pyroclastic flows


  High concentration density flows that are essentially no turbulent and confined to valleys
• Pyroclastic surge


  Low concentration density flows that can expand over hill and valley like hurricanes
• Volcanic eruption impacts


  • Many people and the cities of Pompeii and Herculaneum were destroyed in 79 AD from an eruption of Mount Vesuvius
  • 29,000 people were destroyed by pyroclastic surges at St. Pierre, Martinique in 1902
  • Over 2000 died at Chichonal Volcano in southern Mexico in 1982 from pyroclastic surges
• Lahars


  Part of the family of debris flows that are fluids composed of mixtures of water and particles of all sizes from clay-size to gigantic boulders, originating directly or indirectly from volcanic action
• Debris flows


  Have the viscous consistency of wet concrete, and there is a complete transition to watery floods
• Lahar impacts


  • The 21,000 lives lost at Armero, Colombia, were from a lahar that formed during the eruption of Nevado Del Ruiz in 1985
• Ash Fall


  Less dangerous to human life than to property, traffic and communication
• Lava Flows


  Rarely threaten human life because lava usually moves slowly
• Tephra Falls and Ballistic Projectiles


  Pyroclastic fragments of any size and origin formed on land
• Magma


  Molten rock containing dissolved gases that are released to the atmosphere during an eruption and while the magma lies close to the surface from hydrothermal systems
• Water Vapor


  The most abundant volcanic gas
• Volcanic Hazard Maps


  • Usually display the current or potential extent of dangerous volcanic flows (Lava, pyroclastic or lahar) together with the potential distribution of tephra
• Topography

  • Major factor controlling the distribution of many volcanic hazards, therefore the presentation of relief, traditionally displayed with contour lines is a very important component
• Volcanic Hazard Alert Stages

  1. Stage 1 (green): Volcano in a normal, no actions

  2. Stage 2 (yellow): Volcano is "restless" - increase in seismicity, deformations, plumes of steam or gas, eruption within months or weeks, alert authorities

  3. Stage 3 (orange): Dramatic increase in above activity, small ash and steam eruptions, eruption within days or weeks, public made aware of problem

  4. Stage 4 (red): Continuous seismic activity, increased eruptive activity, evacuate public from hazard zones, eruption within hours or days
• Geologic hazard


  One of several types of adverse conditions of the earth which is capable of causing damage or loss of property and life
• Geology


  The study of the solid earth, which refers to the planet's solid surface and its interiors
• Plate boundaries


  • Convergent (destructive)
  • Divergent (constructive)
  • Transform fault (conservative)
• The Philippines is situated along two major tectonic plates of the world, the Eurasian and Pacific Plates
• Rainfall

  The most important climatic element in the Philippines, with 20-30 typhoons per year according to the National Disaster Coordinating Council
• Landslides induced by rainfall


  Caused by the build up of water pressure into the ground
• Landslide incidents in the Philippines

  • The Cherry Hill Subdivision Landslide in Antipolo on August 3, 1999 during Typhoon Olga
  • The fate of a mountain in Guinsaugon on February 17, 2006 after 10 days of heavy rains and a minor earthquake, burying an estimated 1000 people
  • A major landslide in Compostela Valley on January 5, 2012 during heavy rainfall
• Sinkhole


  A depression or hole in the ground caused by some form of collapse of the surface layer, which can be natural or man-made, often due to changes in natural water-drainage patterns
• Sinkhole incidents in the Philippines

  • Sinkhole in Bantayan Island and Badian, Cebu found in July 2014
  • Mysterious Underwater sinkhole of Dadiangas, GenSan in February 2015
  • Sinkholes in Bohol on October 15, 2013
  • Sinkhole in Kabankalan City, Negros Occidental in July 2014
• Fire


  A common hazard that occurs at home and workplaces which damages properties and causes death
• Fire triangle or combustion triangle


  A simple model for understanding the necessary ingredients for most fires: heat, fuel, and an oxidizing agent (oxygen)
• Heat


  Responsible for the initial ignition of fire, and needed to maintain the fire and permit it to spread
• Fuel


  Any kind of combustible material, characterized by its moisture content
• Oxygen


  Air contains about 21% oxygen, and most fires require at least 16% oxygen to burn
• Combustion


  The chemical reaction that feeds fire more heat and allows it to continue
• Foam


  Can be used to deny the fire the oxygen it needs
• Water


  Can be used to lower the temperature of the fuel below the ignition point or to remove or disperse the fuel
• Halon


  Can be used to remove free radicals and create a barrier of inert gas in a direct attack on the chemical reactions responsible for the fire
• Fire incidents where water cannot be used to put out the fire

  • Electricity is present
  • Hydrocarbon fires, or pool fires, are fuelled by oil and gas and have a very rapid heat
  • Metal fires
  • Oil fires