Volcanic Hazards

• Types of lava hazards:

  1. Lava fountain
  2. Tephra fall/ash fall
  3. Pyroclastic Density Currents
  4. Volcanic gases
• Lava fountain

  • more explosive "spraying" or "fountaining of lava"
• Lava fountain:

  • Ballistic bombs/fragments - ejected and projectiled from the vent, hazardous for near-vent areas
• Lava flow

  • Generally effusive lava outpouring or oozing
• Tephra Fall

  • Tephra, mostly ash, which are erupted to form an eruption column and an eruption cloud, will eventually settle and fall to the ground
• Tephra Fall

  • most widespread volcanic hazard, ash can travel very far if suspended in atmosphere for a long time
• Causes of tephra fall:

  • Respiratory issues
  • Structure collapses due to weight of ash (infrastructure damages)
  • Damages crops
  • Obscure sunlight
  • Disrupts transportation (land and aviation)
• Pyroclastic Density Currents (other names):

  • Pyroclastic flows
  • Pyroclastic surge
  • Base surge
• Pyroclastic Density Currents:

  • Turbulent mass of volcanic materials (ash +rocks) + hot gasses that flow downslope at very high speeds (>60 kph)
• Pyroclastic Density Currents

  • deadliest volcanic hazard
• Causes of PDCs:

  1. burning
  2. burial
  3. asphyxiation
  4. filling valleys with pyroclastic materials
• Lahar

  • Hot or cold mixture of water and rock fragments that flows down the slopes of a volcano and typically enters a river valley
• Causes of lahar:

  1. severe flooding
  2. destruction of lives and properties
• Fumaroles: vents where gasses from magma escape to the surface)
• Volcanic gases

  • Exsolved from magma and may be released in eruption plume or along fumaroles
  • toxic when concentrated
• Volcanic smog (vog)

  • produced from sulfur dioxide
• Carbon dioxide

  • Trapped in low lying areas can be lethal to people and animals
  • 3% CO2 -> headaches, dizziness, increased heart rate and difficulty breathing
  • 15% mixing ratios carbon dioxide quickly causes unconsciousness and death
• Hydrogen halides:

  • HF
  • HCl
  • HBr
• Hydrogen halides

  • strong toxic acids
  • Have high solubility; rapidly dissolve in water droplets within volcanic plumes or the atmosphere
• Sulfur dioxide

  • irritating to eyes, skin and respiratory system
• Hydrogen sulfide

  • Is very toxic in high concentrations
  • Irritation of the upper respiratory tract and during long exposure, pulmonary edema
  • 500 ppm can cause human to fall unconscious (5 mins); die in an hour or less