TOPIC 5: EARTHQUAKE HAZARDS MAPS AND VOLCANOES HAZARD

• seismic hazard map -is the hazard map associated with potential earthquakes in a particular area and shows the

  relative hazards in different areas.
• ground rupture hazard map -shows wherein fault cut across.
• basic parts of a map:

  • Map title
  • symbols
  • legend
  • scale
  • source
• map title - tells you what map is all about
• symbols -the points, lines, shapes, and colors used on the map. For example, a line may indicate faults or tsunamis while a triangular shape may represent a volcano
• legend -details of what each symbol mean
• scale -refer to the bar scale as this helps determine distances
• source -make sure that the source of your map is a credible institution
• volcano -signifies a vent, hill, or mountain from which molten or hot rocks with gaseous materials are or have been ejected. The term also applies to craters, hills or mountains.
• volcanic eruption -is a process wherein molten rock materials are emitted or ejected in the form of flowing masses of lava or fragmental particles called pyroclastic with gas from a crater, vent, or fissure (a narrow opening). 
• volcanic hazard - are phenomena arising from volcanic activity that pose potential threat to persons or property in a given area within

  a given period of time. Below is a list of volcanic hazards common in Philippine active volcanoes. 
• lava flow -stream like flow of incandescent, molten rock material erupted from a volcano.
• lava flow - stream like flow of incandescent, molten rock material erupted from a volcano
• tephra fall or ash fall -shower of fine-to-course grained products of a volcanic eruption. Ashfall is distributed or dispersal is dependent on prevailing wind direction.
• volcanic gas - gases released to the atmosphere in the form of water vapor, hydrogen, sulphide, sulphurndioxide, carbon monoxide, hydrogen chloride, and hydrogen fluoride.
• lahar - rapidly flowing thick mixture of volcanic materials and water, usually generated along river channels by extreme rainfall.
• tsunami or seiche -sea waves or wave trains that are generated by sudden displacement of water (could be generated during undersea eruptions or debris avalanches)
• tsunamis or seiche
• volcanic landslide or debris avalanche -massive collapse of a volcano, usually triggered by an earthquake or volcanic eruption.
• volcanic landslide or debris avalanche
• fissuring -movement/adjustment along faults, accompanied by earthquake.
• hydrothermal explosions -explosions from instantaneous flashinh of stesm upon contact with hot rocks.
• subsidence -ground deformation resulting from the downward adjustment of surface materials to the voids (empty space) caused by volcanic activity.
• two types of explosions : hydrothermal explosions & secondary explosions