VOLCANOES

• PHIVOLCS Definition

  Philippine Institute of Volcanology and Seismology
• Volcanism


  refers to any phenomenon of eruption of molten lava onto the surface, whether from a tall volcano or simply from magma that rises through a crack on a planet’s lithosphere.
• Volcano


  a hill, mountain, or fissure from which molten rocks, hot gases, and ash are ejected
• Crater


  a funnel-shaped depression at the top of a volcano formed as a result

  of explosive eruption
• Caldera


  a volcanic crater that is formed when a part of the wall of the crater collapses following an explosive eruption
• Magma


  comes out of a vent , molten rocks inside the earth
• Lava


  magma that has been ejected out of a volcano
• Types of Volcanic Activity

  • Active - erupted recently

  • Dormant - erupted in the last 2000 years but not recently

  • Extinct - unlikely to erupt again
• Volcanic Structure

  • Cinder - bowl shaped crater

  • Shield - large, broad volcanoes that look similar to shields

  • Composite - large, typically steep-sided, cone-shaped

  • Dome - a dome shaped

  • Caldera - large depressions
• Volcanic Eruptions

  Effusive - quiet or non explosive eruption, calm lava flow, huge amount of lava but less ash and dust

  
  

  Explosive - more destructive, produces clouds of hot ash, gas, and rock fragments, does not produce lava flows
• Type of Eruption

  • Phreatic - steam-driven explosion, magma involvement

  • Vulcanian - explosive eruption, moderate magma viscosity

  • Strombolian - mildly explosive, lava fountaining

  • Pelean - highly explosive eruption with pyroclastic flows

  • Phreatomagmatic - explosive eruption, magma-water interaction

  • Plinian - extremely explosive