5.4

• Tephra falls


  Volcanic rock and lava materials that are ejected into the air by explosions or carried upward by the eruption column's hot gases or lava fountains

  
• Ballistic projectiles


  Rocks that an erupting volcano may hurl into the air, following a projectile path as they are forced out of the vent at steep angles like a cannon ball
• Tephra falls and ballistic projectiles are both types of volcanic hazards that can occur during explosive volcanic eruptions

  
• Tephra


  Volcanic rock and lava materials that are ejected into the air by explosions or carried upward by the eruption column's hot gases or lava fountains

  
• Ballistic projectiles


  • They travel like cannonballs and usually land within 2km of the vent
• Types of tephra falls

  • Ash
  • Lapilli
  • Blocks & Bombs
  • Pele's Tears
  • Pele's Hair
  • Pumice
  • Scoria
• Ash


  3mm diameter fragment, mix of broken glass and pulverized rock

  
• Lapilli


  Size from 2 to 64mm, bigger pumice fragments mixed with finer ash

  
• Pele's Tears


  Small pieces of solidified lava drops formed when airborne particles of molten material fuse into tearlike drops of volcanic glass

  
• Pele's Hair


  A volcanic glass formation produced from cooled lava stretched into thin strands, usually from lava fountains, lava cascades, or vigorous lava flows

  
• Pumice


  A type of extrusive volcanic rock, produced when lava with a very high content of water and gases is discharged from a volcano

  
• Scoria


  A dark-colored volcanic rock formed by ejection as a molten blob and cooled in the air to form discrete grains called "clasts"

  
• Blocks & Bombs


  Size is 64mm above, bombs are molten when ejected and assume various shapes upon cooling, blocks are large broken pieces of solid vent material or surrounding rocks

  
• Dangers of tephra falls and ballistic projectiles

  • Airborne fine particles can harm eyes with conjunctivitis and corneal abrasions
  • Ash accumulation on roofs
  • Ash from distant volcanoes can temporarily isolate small communities and strand people on roadways
  • Ash contains various chemicals, toxic gases, acids, and salts
  • Airborne ash can turn day to night by blocking sunlight
  • Ash clogs many industrial machines and automobiles
• Mitigating the effects


  Refer to the actions or measures taken to reduce or prevent negative impacts or consequences
• Mitigating effects before


  • Availability of protective clothing and high efficiency dust masks before volcano-related emergencies
  • Design roof orientation and pitch to discourage thick tephra buildups
  • Strengthen roofs and walls to withstand loading and projectile impacts
  • Wear protective clothing and high-efficiency dust masks
• Mitigating effects during


  • Patients with lung problems are advised to stay inside their houses to avoid exposure to ash
  • If no approved mask is available, use fabric mask damped with water
  • Keep proper distance between vehicles while driving
  • Clear tephra from roofs as it accumulates
  • Handle the ash in open well-ventilated areas, and wet the dust whenever possible to prevent its movement
• Mitigating effects after


  • Wear goggles or corrective eyeglasses to protect eyes from irritation caused by fine ash
  • Remove or stabilize tephra on the ground to prohibit reworking
  • Personnel not essential to the emergency should be kept inside and made to strictly observe all safety precautions during cleanup
• Tephra falls and ballistic projectiles are two types of volcanic hazards that can occur during explosive volcanic eruptions