fta quiz 1?

• Volcano


  A vent, hill or mountain from which hot and molten rocks (lava), rock fragments, and gaseous materials have been ejected
• Magma


  Molten or hot liquid rock in the Earth's mantle
• Lava


  Magma or molten rock that reached the Earth's surface
• Classification of Magma

  • Basaltic magma (45-55% silicon dioxide, least viscosity)
  • Andesitic magma (55-65% silicon dioxide, moderate viscosity)
  • Rhyolitic magma (65-75% silicon dioxide, greatest viscosity)
• Classification of Volcanoes


  • Stratovolcanoes (most common, conical shape, steep slopes)
  • Shield volcanoes (low, broad, domed, basaltic lava flows)
  • Cinder cone volcanoes (simplest, 30-300m height)
• Signs of an impending Volcanic Eruption


  • Intensified steaming activity with color change
  • Dried-up vegetation, streams and water wells
  • Ground movement or tremors due to volcanic earthquakes
  • Crater glow at or near the crater or summit area
  • Increased frequency of landslides and rockfalls
  • Increased temperature in hot springs and crater lakes
  • Rumbling sound and sulfur smell for residents
  • Sulfur dioxide and other gas emissions
• Lava Flow


  Rivers of incandescent molten rock or lava that erupted from a crater or fissure and moves downslope or away from an eruption vent
• Lava Flow


  • Can be erupted either through a nonexplosive or an explosive lava fountain
  • Speed depends on steepness of slope, type of lava and viscosity, whether in a channel/tube or broad sheet, and lava production rate
• Pyroclastic Fall


  Pyroclastic fragments of rocks, or tephra, ejected and propelled through the atmosphere that fallout from the plumes of a volcanic eruption
• Pyroclastic Flow


  Mixture of pyroclastic fragments (hot lava blocks, pumice, ash) and hot volcanic gases that rush down volcanic slopes at very high speed outward from the source vent
• Pyroclastic Flow


  • Has a basal flow of coarse fragments that moves along the ground, and a turbulent cloud of ash that rises above the basal flow
• Lahar


  Mudflow or debris flow, a mixture of pyroclastic materials and water rapidly flowing down a volcano slope through rivers and channels
• Volcanic Gases


  Gases released to the atmosphere during eruptions, including water vapor, carbon dioxide, carbon monoxide, sulfur dioxide, hydrogen sulfide, hydrogen chloride and hydrogen fluoride
• Volcanic Gases


  • Water vapor is the most abundant and non-toxic/non-poisonous, other gases are toxic/poisonous to people, animals, and agricultural crops