Igneous Structures: Volcanic

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Igneous Structures Volcanic
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Viscosity

• Units pascal-seconds (kg/m-sec)
• How many pascals pressure x how many seconds to
  squash fluid flat?
• Viscous Material flows as long as pressure is
  applied, however small
• Pseudoviscous Material flows after some
  threshold stress

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Viscosity of Common Materials
Material Viscosity Pa-Sec
Hydrogen gas, 15 degrees K 0.0000006 (6 x 10-7)
Air, 0 degrees C 0.000017 (1.7 x 10-5)
Liquid Hydrogen 0.00001 (10-5)
Water 0 degrees C 0.0018 (1.8 x 10-3)
Water 100 degrees C 0.0003 (3 x 10-4)
Heavy Machine Oil 15 C 0.66
Glycerin, 20 degrees C 1.5
Honey 20 degrees C 1.6
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Geologic Viscosities
Material Viscosity Pa-Sec
Basalt Lava 1000
Rhyolite Lava 1,000,000
Rock Salt 1014 (Pseudoviscous)
Marble 1016
Granite, Quartzite 1018 - 1020
Asthenosphere 1019 - 1020
Deep Mantle 1021 - 1022
Shallow Mantle 1023 - 1024
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What Drives Magma?

• Magma is typically 10 lighter than equivalent
  solid rock
• Why pressure inhibits melting
• Buoyancy drives magma upward
• Weight of rock around volcanic conduit gt weight
  of magma
• Gas pressure powers volcanic eruptions
• Mafic (dense) rocks can sink in crust by viscous
  flow

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Plate Tectonics and Volcanoes
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A Cinder ConeWizard Island, Crater Lake, Oregon
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Paricutin, Mexico1943-1952
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Anatomy of a Cinder Cone, Hawaii
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Tuff Ring Diamond Head, Hawaii
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Tuff Ring Diamond Head, Hawaii
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Shield Volcano Haleakala, Hawaii
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Stromboli
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Mount Lassen and Mount Tehama
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Mount Shasta, California
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Shasta and Shastina
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Shastina and Landslide Deposit
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Mount Shasta and Landslide Deposit
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Mount Saint Helens and Spirit Lake
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May 18, 1980
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The Mountain Collapses
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Mount St. Helens
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Mt. St. Helens
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Bezymianny, Russia
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Lava Dome, California
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Rhyolite Plugs and Pumice Rings
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Rhyolite Plugs and Pumice Ring
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Obsidian Dome, California
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Obsidian
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Rhyolite Plugs and Pumice Rings
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Maar, Nevada
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Volcanic Neck, New Mexico
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Topographic Inversion, Nevada
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How Calderas Form
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Crater Lake, Oregon
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Mount Mazama After
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Mount Mazama Before
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Jemez Caldera, New Mexico
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Valles Caldera, New Mexico
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Tuff, Valles Caldera, New Mexico
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Welded Tuff, California
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Santorini (Thera), Greece
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Santorini (Thera), Greece
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Santorini, Greece
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Santorini, Greece
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Ash Layer, Santorini
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Ash Layers, Santorini
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What Really Destroyed the Minoan Civilization
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(No Transcript)
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Collapsing Volcanoes - Hawaii
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Molokai Scarp
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Nuuanu Pali, Oahu
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Tambora 1815

• 1816 Year Without A Summer
• 100 cubic km of ash erupted
• Global sunset color effects for months
• New England
• Snow in June and August, Frost in July
• Exodus to Midwest
• Europe High prices, food riots

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Tambora
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Long Valley Caldera
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Long Valley Caldera
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Bishop Tuff
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Compaction of Bishop Tuff
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Toba, Sumatra
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Eyjafjallajokull, Iceland
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Flood Basalts, Washington
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Lava Delta, Washington
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Columnar Jointing, Washington