Effects of a Volcanic Eruption

Primary Effects

  • Lava flows – although lava is the greatest perceived threat it rarely moves fast enough to kill people before they are evacuated. However, lava flows that cannot be diverted can cause damage.
  • Pyroclastic flow – during and after the initial eruption gas and volcanic debris can be hurled down the mountainside at speed of up to 150mph. This fast-moving cloud of material is known as a Nuee Ardente and can flatten or bury buildings in its path.
  • Pyroclastic fall – ash and debris fall steadily after an eruption. The fine rock particles can damage people’s lungs while heavier particles can flatten crops or cause roofs to collapse. Ash particles can cause engine failure in aircraft or cause climate change or global cooling.
  • Lahars – results when volcanic debris combines with large quantities of water. The lahar can be very fast moving (up to 100mph) and can bury settlements before evacuation. Lahars can form when volcanoes erupt into glaciers, crater lakes or when the volcano produces large quantities of steam.
  • Poisonous gases – CO2 and CO can spill down a volcano unseen collecting in hollows in valleys causing asphyxiation.


Secondary Effects

  • Shortage of food and clean water due to crops failing and contamination of water systems.
  • People are left homeless.
  • Infrastructure is destroyed.
  • Airports close so loss of money via tourism.