Week 7

• Seismic hazard map is the hazard map associated with potential earthquakes in a particular area and shows the relative hazards in different areas.​
• For earthquakes, a ground shaking hazard map shows the distribution of earthquake shaking levels that have a certain probability of occurring. ​
• Before using the map, be sure that you understand the basic parts:​ a. Map Title; b. Symbols; c. Legend; d. Scale; e. Source
• Source​

  make sure that the source of your map is a credible institution
• Scale​

  refer to the bar scale as this helps determine distances, etc.
• Legend ​

  details of what each symbols mean
• 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
• Map title ​

  tells you what map is all about
• 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). ​
• 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 hazards are phenomena arising from volcanic activity that pose potential threat to persons or property in a given area within a given period of time. ​
• Pyroclastic Flow ​

  Fast turbulent mass of fragmented volcanic material (ash and rocks) mixed with hot gases that flows downslope at very high speed (>60kph) ​
• Lava Flow​

  Stream-like flow of incandescent, molten rock material erupted from a volcano ​
• Lava Flow​

  -Lava flows rarely threaten human life because lava usually moves slowly -- a few centimeters per hour for silicic flows to several km/hour for basaltic flows. ​
• Tephra Fall or Ashfall ​

  Shower of fine-to-coarse 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, sulphur dioxide, carbon monoxide, hyrogen 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) ​
• Volcanic Landslide or Debris Avalanche ​

  Massive collapse of a volcano, usually triggered by an earthquake or volcanic eruption ​
• Fissuring ​

  Movement/ adjustment along faults, accompanied by earthquake​
• • Hydrothermal Explosions ​

  Explosions from instantaneous flashing of steam upon contact with hot rocks. ​
• Secondary Explosions ​

  Non-eruption explosive events generated when water comes in contact with still hot pyroclastic-flow deposits the stage of a volcano and converted to steam ​
• Subsidence ​

  Ground deformation resulting from the downward adjustment of surface materials to the voids (empty space) caused by volcanic activity.​