DIFFERENT TYPES OF VOLCANIC HAZARDS

• PYROCLASTIC FLOWS AND SURGES

  can destroy anything on its path

  by direct impact, burn sites with hot rock debris,

  burn forests, and farmlands, and destroy crops

  and buildings
• PYROCLASTIC FLOWS AND SURGES

  (Pyroclastic density current) are turbulent

  masses of ejected fragmented volcanic materials

  (ash and rocks), mixed with hot gases (200oC to

  900oC) that flow downslope at very high speeds

  (>60kph).
• PYROCLASTIC FLOWS AND SURGES

  Pyroclastic flows and surges are potentially

  highly destructive owing to their mass, high

  temperature, high velocity, and great mobility.
• PYROCLASTI C FLOWS AND SURGES

  Deadly effects include asphyxiation (inhalation of

  hot ash and gases), burial, incineration (burns),

  and crushing from impacts.
• Ballistic projectiles

  are volcanic materials directly ejected from the

  volcano’s vent with force and trajectory. These

  endanger life and property by the force of impact

  of falling fragments, but this occurs only close to

  an eruption vent.
• LAVA FLOWS are stream-like flows of glowing molten rock

  erupting from a crater or fissure.
• LAVA FLOWS When lava is

  degassed and/or very viscous, it tends to extrude

  extremely slowly, forming lava domes
• LAVA FLOWS

  Major hazards of lava flows include burying,

  crushing, covering, and burning everything in their

  path. The intense heat of lavas melts and burns.
• Collapsing viscous lava domes

  can trigger dangerous pyroclastic flows.
• ASHFALL OR TEPHRA FALLS

  Are showers of airborne fine-grained to

  coarse-grained volcanic particles that fall out

  from the plumes of a volcanic eruption; ashfall

  distribution/ dispersal is dependent on prevailing

  wind direction.
• ASHFALL OR TEPHRA FALLS

  cause poor or low visibility which

  may affect driving and cause slippery roads
• ASHFALL OR TEPHRA FALLS

  If burial by ashfall is greater than 10 cm in depth, it

  can render agricultural lands useless.
• LAHARS

  are a rapidly flowing thick mixture of volcanic

  sediments (from the pyroclastic materials) and

  water, usually triggered by intense rainfall during

  typhoons, monsoons, and thunderstorms
• Lahar

  can occur immediately after an eruption or can

  become a long-term problem if there are

  voluminous pyroclastic materials erupted.
• LAHARS

  It can lead to increased deposition of sediments

  along affected rivers and result in long-term

  flooding problems in the low-lying downstream

  communities.
• Volcanic GASES AND AEROSOLS

  released into the

  atmosphere include water vapor (H2O), hydrogen

  sulfide (H2S), sulfur dioxide (SO2), carbon

  monoxide (CO), hydrogen chloride (HCl), and hydrogen fluoride (HF)
• SO2, CO2, and HF are

  some volcanic gases that pose hazards to

  people, animals, agriculture, and property.
• SO2 can lead to acid rain
• High concentrations of CO2 can be lethal to people, animals, and vegetation.
• Fluorine compounds can deform and kill animals

  that graze on vegetation covered with volcanic

  ash.
• Volcanic Landslide OR Debris Avalanche is a massive collapse of a volcano, usually

  triggered by an earthquake or volcanic eruption.
• Volcanic Landslide OR Debris Avalanche

  The huge volcanic debris avalanche typically

  leaves an amphitheater-like feature and at the

  base of volcanoes with debris avalanche events,

  a hummocky topography (small hills all over).
• Tsunami An eruption that occurs near a body of water may

  generate tsunamis if the pyroclastic materials

  enter the body of water and cause it to be

  disturbed and displaced, forming huge waves
• HOW CAN WE TELL WHEN A VOLCANO WILL

  Erupt? It can also deform the ground surface and cause

  anomalous heat flow or changes in the temperature

  and chemistry of the groundwater and spring waters.
• Steam-blast eruptions, however, can occur with little

  or no warning as superheated water flashes to steam.