VOLCANOES 2

• when magma is ejected out of the volcano it is called lava. When it cools and solidifies it is known as laneous rock.
• Magma can be classified into basaltic or mafic, intermediate or andesitic and granitic or felsic.
• Factors affecting volcanic eruption

  • Magma’s temperature
  • Chemical composition
  • Viscosity
  • Amount of dissolved gases it contains
• Viscosity

  • the property of the material‘s resistance to flow.
• Basaltic magma or mafic

  • viscosity: low
  • temperature: 1000 to 1200C
  • Gas content: 1-2%
  • Explosiveness: least explosive
  • Location of formation: Both oceanic and continental
• Andesitic or intermediate magma

  • Viscosity: Intermediate
  • temperature: 900-1000C
  • gas content: 3-4%
  • Silica content: 60%
  • explosiveness: intermediate
  • Location of formation: Continental margins associated with subduction zones.
• Rhyolitic magma

  • Viscosity:high
  • Temperature: 760-900C
  • Gas content: 4-6
  • Silica content: 70%
  • Explosiveness: most explosive
  • Location of formation: continental crust
• Icelandic

  • characterized by effusions of molten basaltic lave that flow from such long, parallel fissures. Such as outpourings often build lava plateaus.
• hawaiian

  • Fluid lava flows from a volcano summit and radial fissures to form shield volcanoes. They are quite large and has gentle slopes.
• Strombolian

  • Involve moderate burst of expanding gases that eject clot of incandescent lava in cyclical or nearly continuous small eruptions.
  • Because of such small frequent outburst, stromboli volcano, located on stromboli island off the northeast coast of italy, has been called the lighthouse of the mediterranean.
• Vulcanian

  • named after the vulcano island near stromboli, generally involves moderate explosions of gas laden with volcanic ash.
  • This mixture forms dark, turbulent eruption clouds that rapidly ascend and expand in convoluted shapes.
• Pelean

  • associated with explosive outburst that generate pyroclastic flow, dense mixtures of hot volcanic fragments and gas.
  • Named after for the destructive eruption of mount pelee on the caribbean island of martinique in 1902.
• Plinian

  • intensely violent kind of volcanic eruption
• Ash fall - pulverized rocks, sand, gritty and harsh glasses shoot out in the air by volcano.
• Mud flow - mixture of water, molten rocks and debris flowing down from the side of volcano to the ground. It is called lahar.
• Lava flow - streams of molten rocks and other fragmented materials emitted by erupting volcano.
• Pyroclastic flow - fast moving hot mixtures of gas, ash, and molten rocks moving away from the volcano to the ground.
• advantages of volcanic eruption: soil fertility, atmospheric cooling, land formation, tourism, raw material.