volcanoes

• basaltic lava forms at constructive plate margins
• features of basaltic lava:

  • hot , low viscosity
  • flows easily and quickly
  • eruptions of balsaltic lava are frequent , go on for long time
• andesitic and rhyolitic lava forms at destructive plate margins
• features of andesitic and rhyolitic lava:

  • cooler , high viscosity
  • flows less easily
  • erupt intermittently and eruptions are short
• types of volcanic hazards

  • nuees ardentes (pyroclastic flows)
  • lava flows
  • mudflows / lahars
  • volcanic gases
  • tephra / ash fallout
• pyroclastic flows are otherwise known as nuee ardente
• pyroclastic flows are a mixture of gas , ash , volcanic rock that flows down slopes due to gravity
• pyroclastic flows travel at high speeds - 80km/mph
• pyroclastic flows normally occur in composite and strato volcanoes
• strato volcanoes are volcanoes made up of layers of lava and tephra
• Mount Pelee , Martinique eruption happened in 1902
• Mount Peel eruption caused pyroclastic flows - 30,000 killed
• pyroclastic flows destroy anything in it's path
• lahars (aka mudflows) is when ash mixes with large amounts of water
• lahars can occur years after volcanoes have stopped erupting
• lahars flow quickly - 80mph
• Montserrat Eruption 1995 - Capital , Plymouth, was covered in ash and mud
• lahars can be monitored by acoustic monitoring and can be channelled away from buildings and people via concrete barriers
• lava at destructive plate margins

  andesitic and rhyolitic
• lava at constructive plate margins

  basaltic lava
• example of a destructive margin

  the Japan Trench
• example of a constructive margin

  Mid-Atlantic Ridge
• pyroclastic fallout + ash fallout

  material that's been ejected from volcano , falls back to ground
• what's tephra

  rock fragments and particles ejected by a volcanic eruption.
• social impacts of volcanic eruption

  • loss of schools and community activity
  • people killed and buildings destroyed by pyroclastic flows
  • pyroclastic + lava flows = wildfires
  • mudflows + flooding from ice melting = drowning + death
• economic impacts of volcanic impacts

  • infrastructure and businesses destroyed
  • damage to buildings = expensive
  • eruptions can boost economy = boost tourism
  • ash clouds can prevent aircraft flying + damage crops
  • damage economy to region = trade deficit
• political impacts of volcanic impacts

  • damage to crops = food shortages + food insecurity
  • gov spends money on repairs rather than developing country
  • looting + violence
• environmental impacts of volcanic hazards

  • Haze effect - sunlight blocked out , reduce temperatures
  • volcanic gases = contribute to enhanced greenhouse effect = global warming
  • ash = damage machines for power + water supply
  • acid rain can lead to acidification of aquatic ecosystems + damages leaves of trees , removes nutrients from soil
• example of where the Haze Effect had detrimental impacts

  Tambora Volcano in Indonesia (1815) - turned summer into winter across the northern hemisphere
• prevention for volcanic hazards

  • volcanic hazard's can't be stopped
  • authorities can use land use zoning to prevent buildings being constructed around the eruption site
  • evacuation
• preparedness for volcanic hazards

  • individuals can invest in an emergency shelter + emergency kit
  • search and rescue + fire response units can be set up
• prediction for volcanic hazards

  • increased seismic waves
  • swelling of volcanoes : gases and magma build up close to surface = TILTOMETERS
• risk management for volcanic hazards

  • land use zoning
  • lahars can be prevented by draining lakes in volcanic crates