volcanic eruption

• Volcanic eruption


  The expulsion of gases, rock fragments, and/or molten lava from within the Earth through a vent onto the Earth's surface or into the atmosphere
• Main kinds of volcanic eruptions


  • Violent/Explosive Eruption
  • Effusive/Quiet Eruption
• Violent/Explosive Eruption


  • Magma erupts explosively as it rises, producing rock fragments (pyroclasts), gas explosions, and thick, sticky lava that doesn't flow easily. Greater threat, more gas emitted.
• Effusive/Quiet Eruption


  • Magma rises and flows out as viscous lava that flows downhill easily and builds up gently.
• Main causes of volcanic eruptions

  • Buoyancy of the magma
  • Pressure from exsolved gases in the magma
  • Increase in pressure on the chamber lid
• Signs of impending volcanic eruption


  • Steam-blast (phreatic) eruptions
  • Earthquakes, ground deformation, unusual heat flow or changes in groundwater
  • Swelling of the ground surface detected by instruments
  • Changes in heat flow measured by infrared surveys or temperature monitoring
  • Changes in fumarolic gas composition
• Lahar


  A hot or cold mixture of water and rock fragments flowing down volcano slopes
• Volcanic ash


  Tiny jagged rock and glass particles blasted into the air
• Pyroclastic flow


  High-density mix of hot lava blocks, pumice, ash and gases moving at high speed
• Ballistic projectiles


  Rocks hurled into the air like cannonballs, usually landing within 2-5 km
• Volcanic gases


  Dissolved gases in magma that provide the driving force for eruptions
• Lava flow


  Streams of molten rock that pour or ooze from an erupting vent