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Igneous Structures: Volcanic PowerPoint PPT Presentation


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Igneous Structures: Volcanic. 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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Igneous Structures: Volcanic

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Igneous Structures: Volcanic


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


Viscosity of Common Materials


Geologic Viscosities


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 > weight of magma

  • Gas pressure powers volcanic eruptions

  • Mafic (dense) rocks can sink in crust by viscous flow


Plate Tectonics and Volcanoes


A Cinder Cone:Wizard Island, Crater Lake, Oregon


Paricutin, Mexico1943-1952


Anatomy of a Cinder Cone, Hawaii


Tuff Ring: Diamond Head, Hawaii


Tuff Ring: Diamond Head, Hawaii


Shield Volcano: Haleakala, Hawaii


Stromboli


Mount Lassen and Mount Tehama


Mount Shasta, California


Shasta and Shastina


Shastina and Landslide Deposit


Mount Shasta and Landslide Deposit


Mount Saint Helens and Spirit Lake


May 18, 1980


The Mountain Collapses


Mount St. Helens


Mt. St. Helens


Bezymianny, Russia


Lava Dome, California


Rhyolite Plugs and Pumice Rings


Rhyolite Plugs and Pumice Ring


Obsidian Dome, California


Obsidian


Rhyolite Plugs and Pumice Rings


Maar, Nevada


Volcanic Neck, New Mexico


Topographic Inversion, Nevada


How Calderas Form


Crater Lake, Oregon


Mount Mazama: After


Mount Mazama: Before


Jemez Caldera, New Mexico


Valles Caldera, New Mexico


Tuff, Valles Caldera, New Mexico


Welded Tuff, California


Santorini (Thera), Greece


Santorini (Thera), Greece


Santorini, Greece


Santorini, Greece


Ash Layer, Santorini


Ash Layers, Santorini


What Really Destroyed the Minoan Civilization


Collapsing Volcanoes - Hawaii


Molokai Scarp


Nuuanu Pali, Oahu


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


Tambora


Long Valley Caldera


Long Valley Caldera


Bishop Tuff


Compaction of Bishop Tuff


Toba, Sumatra


Eyjafjallajokull, Iceland


Flood Basalts, Washington


Lava “Delta,” Washington


Columnar Jointing, Washington


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