Volcanology of Yellowstone


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A presentation on the volcanic history and future of Yellowstone, designed for an introductory college course on volcanology.

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Volcanology of Yellowstone

  1. 1. Volcanism at Yellowstone Presentation by Tara K. Blalock
  2. 2. Presentation Objectives: • Become familiar with the geography of Yellowstone • Explore Yellowstone hotspot theory • Introduce 3 phases of Yellowstone volcanism • Dissect geology of Yellowstone volcanic deposit • Interpret Yellowstone hydrothermal processes • Predict future volcanic activity at Yellowstone
  3. 3. Geography of Yellowstone A ppr ox here! imately 1 760 m i from Image taken from Google
  4. 4. Geography of Yellowstone Approximate path of Yellowstone volcanism Image taken from Google
  5. 5. Geography of Yellowstone - 100 eruptions over 16.5 million years - 7 historic calderas Image from Smith et. al.
  6. 6. Geography of Yellowstone Image taken from Google
  7. 7. Geography of Yellowstone Sour Creek “resurgent dome” Mallard Lake “resurgent dome” Image from Wicks, et. al.
  8. 8. The Yellowstone Hotspot Traditional Hotspot Theory: A mantle “plume” originating at the core-mantle boundary facilitates upward melting and volcanism at the surface Continental Crust Lithospheric Mantle Mantle Outer Core
  9. 9. The Yellowstone Hotspot Newer Yellowstone Hotspot Theory: - Radioactive decay and decompression melting within the asthenospheric mantle at only 125 miles depth provides the hotspot origin - Sheering at the lithospheric boundary causes a 300-mile magma pool - Basalt melt “blobs” from the mantle melt granitic crustal rock Upper Crust Lower Crust 25 mi Lithosphere 50 mi 75 mi 100 mi Upper Aesthenosphere U U U U
  10. 10. 3 Eruption Phases Using seismic tomography on the Snake River Plain, 3 eruption phases have been determined for the Yellowstone hotspot: 2.“Pre-Yellowstone” phase: basaltic pooling at the mantle-lithosphere boundary 3.“Yellowstone” phase: rhyolitic explosive eruptions and flows 4.“Snake River Plain” phase: basaltic flows
  11. 11. Phase 1: “Pre-Yellowstone” Phase Rising basaltic magma from 125 miles within the asthenospheric mantle pools at the base of the lithosphere, and produces a topographic “bulge” on the surface approximately 300 miles in width 300 miles Upper Crust Lower Crust 25 mi Lithosphere 50 mi 75 mi 100 mi Upper Asthenosphere U U U U
  12. 12. Phase 2: “Yellowstone” Phase - The “supervolcano” phase…basaltic magma rises and melts the lower crust, producing a silica-rich magma chamber. - Rising magma bulges the surface, which causes faulting and earthquakes in a ring around the chamber. - Faults that reach the magma chamber cause rapid decompression within, which allows volatiles to expand at supersonic speeds and rhyolitic lava to erupt. - A catastrophically explosive eruption forms a massive caldera. The current Yellowstone caldera is 28 miles by 45 miles. Upper Crust Lower Crust Lithosphere
  13. 13. Phase 2: “Yellowstone” Phase - Post-caldera eruptions - rhyolite flows - eventually fill the caldera. - Yellowstone’s last post-caldera rhyolite eruption was 70,000 years ago. Rhyolite tuff: a single cooling unit formed during caldera- forming eruptions Rhyolite flow: post-caldera
  14. 14. Phase 3: “Snake River Plain” Phase - Without the hotspot, the silica-rich magma within the chamber cools more quickly than the silica-poor basaltic magma, allowing the basalt to erupt. - It levels the landscape and helps the elevation to subside.
  15. 15. Volcanic Deposit Dark = primarily magnetite and pyroxine Light = large pieces mostly crystalized pumice; smaller are pumice, feldspar and quartz Tuff Cliff: Image from USGS Bulletin 1347 Tuff Deposit: Image from USGS Bulletin 1347
  16. 16. Volcanic Deposit Rhyolite flow Image from USGS Bulletin 1347
  17. 17. Volcanic Deposit Image from Fool-On-The-Hill Image from USGS Bulletin 1347 Black = obsidian Light = feldspar and quartz Image from USGS Bulletin 1347
  18. 18. Volcanic Deposit Basalt flows! Columnar jointing Image from Ellenm1 Image from Piedmont Fossil
  19. 19. Hydrothermal Processes Angel Terrace Thermal Pool, Lower Geyser Basin Image from Kris Taeleman Image from AR Nature Gal Clepsydra Geyser Thumb Paint Pots Image from ZaNiaC Image from Serene Silence
  20. 20. Hydrothermal Processes Image from USGS Bulletin 1347
  21. 21. Future Volcanism at Yellowstone A breathing landscape? Image from Wicks, et. al.
  22. 22. Future Volcanism at Yellowstone seismicity? Increased Image from USGS, 2009
  23. 23. Future Volcanism at Yellowstone Changes in hydrothermal activity? Old Faithful Image from Kris Taeleman
  24. 24. Conclusions •Evidence shows it is likely that Yellowstone will erupt again, although the magnitude of the eruption is uncertain •Close monitoring of uplift and subsidence, seismic and hydrothermal data will likely indicate future volcanic activity
  25. 25. Image from Human Nature