Volcanism

• Diastrophism


  Horizontal and vertical movement of the crust
• Erosion


  Physical removal of rock due to running water, glacial ice and wind or changes in ground water
• Volcanism


  Phenomenon related to various processes associated with surface discharge of magma or hot water
• Cone


  • Most striking part of a volcano, composed of a mixture of lava and pyroclastic materials
  • Granitic magma forms high sided steep cones, basaltic magma creates low to almost flat cones
• Vent


  Opening through which eruption takes place
• Magma chamber


  Large underground pool of liquid rock
• Crater


  Basin-like depression over a vent or summit of a volcano
• Caldera


  Volcanic depression much larger than the original crater
• Sills


  Horizontally intrusive sheets that originally forced their way parallel to the older layer of rocks
• Dikes


  Vertical intrusion of magma along the cracks on the crust
• Conduit


  Pipe conveying liquid material such as magma
• Flank


  Side of a volcano
• Summit


  Highest point or apex of a volcano
• Throat


  Entrance of a volcano
• Ash cloud


  Expelled in the atmosphere
• Volcanic material


  • Volcanic bombs/lapilli
  • Tephra fall (fragmented material consisting of pumice, scoria, crystals)
• Pyroclastic flow


  Fast moving current of hot gases and rock traveling downhill from a volcano
• More water


  Bigger explosion
• Easy escape (low pressure)

  Quiet eruption
• Difficult to escape (high pressure)


  Explosive/violent eruption
• Basaltic (thin)


  Quiet eruption
• Granitic(Rhyolitic)/Andesitic (thick)


  Violent eruption
• Shield Volcano


  • Formed by quiet eruptions
  • Slow-moving lava flows
  • Basaltic lava builds up in flat layers
  • Largest with gently sloping sides
• Cinder Cone Volcano


  • Caused by explosive eruptions
  • Granitic lava thrown high into the air
  • Steep-sides, lose slopes
• Composite Volcano


  • Mix of the other two types
  • Can be quiet or violent
  • Can be basaltic or granitic
  • Can have steep or gentle slopes
  • Layered of tephra
• Calderas


  Huge crater formed by the collapse of the volcano when magma rapidly erupts from underneath it
• Active volcano


  One that is erupting or has shown signs that it may erupt in the near future
• Dormant volcano


  Volcano to awaken in the future and become active
• Extinct volcano


  Dead volcano, not likely to erupt again