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Regional Geology

Columbia Plateau. Willamette Valley. Regional Geology. Justin Filiberto LPI. Some questions to ponder…. Is this process constructional or destructional? How? Why? What ways? What is the time scale of this processes? Catastrophic? Long term? How will I recognize it in the field?

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Regional Geology

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  1. Columbia Plateau Willamette Valley Regional Geology Justin Filiberto LPI

  2. Some questions to ponder… • Is this process constructional or destructional? • How? Why? What ways? • What is the time scale of this processes? • Catastrophic? • Long term? • How will I recognize it in the field? • Does this processes have implications for other planetary bodies?

  3. Blue Mountains • Accreted huge blocks of 5 terranes • Olds Ferry: island arc and sediments • Layered rocks from the forearc basin • Baker terrane: deep ocean crust • Grindstone terrane: shallow ocean basin • Wallowa: volcanic arc • Oldest rocks in Oregon • Triassic

  4. Coastal Rangeand Willamette Valley

  5. Coastal Rangeand Willamette Valley • Accreted volcanic seamounts • Undersea mountains • Small volcanic islands • Accreted coastal marine sediments • Later altered by glacial events

  6. Klamath Mountains

  7. Klamath Mountains • Accreted exotic terranes • Oceanic crust (Josephine Ophiolite) • Ocean floor sediments • Island arc volcanoes • Numerous terranes added together like fallen dominoes

  8. Cascades

  9. Cascades • Subduction related volcanism • Dehydration of subducting slab • Fluid induced melting of overlying mantle • Volatile-rich, silica-rich magma • Explosive eruptions • Stratovolcanoes

  10. Basin and Range

  11. Basin and Range

  12. High Lava Plains

  13. High Lava Plains • “Young” eruptions (< 10 million years) • Magma rose though cracks in the crust • Brothers fault zone • Bimodal lava compositions • Basalts from “deep” • Rholites produced from shallow hydrous melting • Thin crust due to stretching (basin and range) • Examples: • Lava Butte • Newberry Crater • Fort Rock

  14. Columbia River

  15. Columbia River • Huge out pouring of basaltic lava • Release of lava from emplacement of mantle plume • Details and interaction with subduction are still debated.

  16. Subduction Factory Explains all volcanism except Columbia River Basalts

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