Volcanoes

• Classification of volcanoes by shape

  • Shield
  • Composite (Stratovolcano)
  • Cinder (ash)
  • Acid (dome)
  • Caldera
• Composite (Stratovolcano)

  • Made of many layers of solidified lava and volcanic ash from different eruptions
  • Lava is slow flowing and solidifies quickly
  • Produces steeply sloping sides
  • Ash occurs in explosive eruptions, often after the vent has become blocked with solidified lava
  • Occur at converging plate margins
• Cinder (ash) volcano


  • Gas forces lava high into the air, where it breaks into small fragments
  • Fragments cool and fall as cinders
  • Produces a short, symmetrical cone with relatively steep sides and a crater at the top
  • Often occur on the sides of shield or composite volcanoes
  • Many are formed from just one eruption
• Acid (dome) volcano


  • Viscous, acid lava erupts effusively but cannot flow far before solidifying
  • Lava builds up to form a steep-sided cone
• Caldera


  • Gases trapped in a magma chamber eventually cause an extremely explosive eruption
  • The upper part of the volcano can be destroyed
  • The ground above the magma chamber can subside, leaving a large depression, which can eventually flood
• Shield volcanoes


  • Effusive eruption where large quantities of lava pour from a central vent
  • Lava travels long distances before solidifying
  • Produces tall volcanoes with gently sloping sides
  • Eruptions tend to be frequent but not explosive
  • Occur at diverging plate margins and hotspots