Definitions

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Definitions

• Section 9.2

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Magma and Erupted Materials

• Viscosity A substances resistance to flow (high
  viscosity honey, low water)
• Lava Magma that reaches Earths surface

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• Pahoehoe Solidified basaltic lava flow on land
  that has formed with smooth, ropelike surfaces
• Aa A solidified basaltic lava flow on land that
  has formed with rough, jagged surfaces

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• Lahar a fast-moving mudflow that occurs when
  heat of a volcano melts the snow and ice on top
  of a volcano
• Pillow Lava Lava that cools underwater, taking
  on a distinctive pillow-like shape as it hardens

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• Pyroclastic material solid rock fragments that
  are ejected during a volcanic eruption
• Pyroclastic flow A dense, superheated cloud of
  gases and pyroclastic materials that moves
  rapidly downhill from a volcanic eruption

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Felsic and Mafic Magmas

• Felsic (Feldspar Silica) magma light-colored,
  high silica, low density, slow moving and
  typically come out of explosive volcanoes
• Mafic (Magnesium ferric) magma darker in color,
  low silica, high density, more fluid, and flow
  more easily. Usually flows smoothly onto the
  surface

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Characteristics of Magma
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Please copy this chart in your notes
Basaltic Magma Andesitic Magma Rhyolitic Magma
Silica Content
Gas Content
Viscosity
Type of Eruption
Melting Temp.
Location
Example
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Basaltic Magma Andesitic Magma Rhyolitic Magma
Silica Content Least (50) Intermediate (60) Most (70)
Gas Content
Viscosity
Type of Eruption
Melting Temp.
Location
Example
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Basaltic Magma Andesitic Magma Rhyolitic Magma
Silica Content Least (50) Intermediate (60) Most (70)
Gas Content Least Intermediate Most
Viscosity
Type of Eruption
Melting Temp.
Location
Example
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Basaltic Magma Andesitic Magma Rhyolitic Magma
Silica Content Least (50) Intermediate (60) Most (70)
Gas Content Least Intermediate Most
Viscosity Least viscous Intermediate Most viscous
Type of Eruption
Melting Temp.
Location
Example
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Basaltic Magma Andesitic Magma Rhyolitic Magma
Silica Content Least (50) Intermediate (60) Most (70)
Gas Content Least Intermediate Most
Viscosity Least viscous Intermediate Most viscous
Type of Eruption Rarely explosive Sometimes explosive Usually explosive
Melting Temp.
Location
Example
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Basaltic Magma Andesitic Magma Rhyolitic Magma
Silica Content Least (50) Intermediate (60) Most (70)
Gas Content Least Intermediate Most
Viscosity Least viscous Intermediate Most viscous
Type of Eruption Rarely explosive Sometimes explosive Usually explosive
Melting Temp. Highest Intermediate Lowest
Location
Example
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Basaltic Magma Andesitic Magma Rhyolitic Magma
Silica Content Least (50) Intermediate (60) Most (70)
Gas Content Least Intermediate Most
Viscosity Least viscous Intermediate Most viscous
Type of Eruption Rarely explosive Sometimes explosive Usually explosive
Melting Temp. Highest Intermediate Lowest
Location Rifts, oceanic hot spots Subduction Boundaries Continental hot spots
Example
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Basaltic Magma Andesitic Magma Rhyolitic Magma
Silica Content Least (50) Intermediate (60) Most (70)
Gas Content Least Intermediate Most
Viscosity Least viscous Intermediate Most viscous
Type of Eruption Rarely explosive Sometimes explosive Usually explosive
Melting Temp. Highest Intermediate Lowest
Location Rifts, oceanic hot spots Subduction Boundaries Continental hot spots
Example Kilauea, Hawaii Mount St. Helens, Washington Yellowstone caldera, Wyoming
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Video Volcanoes 101-NatGeohttps//www.youtube.co
m/watch?vyDy28QtdYJY Mt. Etna