1 / 32

By: David P. Hill, Roy A. Bailey, and Alan S. Ryall

Active Tectonic and Magmatic Processes Beneath Long Valley Caldera, Eastern California: An Overview. By: David P. Hill, Roy A. Bailey, and Alan S. Ryall. Presented by: Kristin Hepper. Long Valley Caldera at a Glance …. Long Valley Caldera. 150 years of earthquake activity M 5-6 level

dinesh
Download Presentation

By: David P. Hill, Roy A. Bailey, and Alan S. Ryall

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Active Tectonic and Magmatic Processes Beneath Long Valley Caldera, Eastern California: An Overview By: David P. Hill, Roy A. Bailey, and Alan S. Ryall Presented by: Kristin Hepper

  2. Long Valley Caldera at aGlance…

  3. Long Valley Caldera • 150 years of earthquake activity • M 5-6 level • The last 10,000-20,000 years

  4. Most Recent Eruptions • Most recent = 500-600 years ago along Inyo/Mono craters chain • These are the most recent caldera forming eruptions within the boundaries of the US • Except for the Cascades

  5. Inyo Craters

  6. The Long Valley Region • Is the boundary between the Sierra Nevada and Basin and Range Provinces • Contemporary encroachment of Basin and Range into the Sierra Nevada

  7. October 1978- M 5.7 earthquake 1 ½ years later- swarmlike sequence of M6 earthquakes within 48hrs of each other This was the onset of the inflation of the resurgent dome Recent History

  8. Next 3 years- • Moderate earthquake swarms and rapid fire sequences • Continued inflation • This raised concerns • Large earthquake • Renewed volcanic activity in the area

  9. History of Volcanic Activity • Volcanism began ~3.2mya • Began with displacement of the Sierran frontal fault scarp • There were basaltic eruptions extending over a 4,000km2 area

  10. Volcanic Activity cont… • The area existed in a potentially explosive state for 400,000 years • 0.73mya a 600km3 of magma was ejected from the magma chamber • Now called the Bishop Tuff

  11. The Bishop Tuff • Covered 1500km2 • Thickness=1500m within the 17 by 32 km Long Valley Caldera • The caldera formed by collapse

  12. The Bishop Tuff

  13. Youngest Eruptions • Inyo/Mono craters chain • Erupted roughly every 500 years for the last 2-3000 years • N trending dike 8-12km long, 200 m from the surface

  14. Future eruptions will be from the younger and more frequently active Mono/Inyo crater chain

  15. The magma chamber Resurgent dome • Seismic measurements • Roof=6-7km beneath resurgent dome • Volume of present magma chamber is between 500 and 1000km3

  16. Closer to recent business • Began in fall of 1978 • Inflation of resurgent dome • Cumulative uplift of resurgent dome=50cm

  17. The cause of the earthquakes • NE-SW extension • Between mid 1979 and ~1984, resurgent dome increased its volume by 0.1-0.2km3

  18. Geothermal… • Intermediate between the giant Yellowstone and the smaller Valles calderas • Shallow convective hydrothermal system • There are active thermal springs and fumaroles at Casa Diablo and Hot creek • Fed by 100-170°C (212-338 °F) water

  19. The Geothermal System-Mammoth geothermal power facility (produces 40Mw of electrical energy)

  20. Comparison with other Calderas • 200 calderas around the world have shown unrest • During a “typical” year, 14 calderas show some signs of unrest • Ground deformation in 3 • Eruptions from 6-7

  21. Other calderas out there… • Long Valley is one of the 4 major calderas in the world • Includes: Rabaul in New Guinea, the Phlegraean Fields in Italy, Long Valley in California, and Yellowstone in Whyoming

  22. Keep in mind • The Inyo/Mono craters erupted 500-600 years ago • Erupted ~2km3 of material • Each vented ejected ~0.2km3 of material • Produced ash falls and pyroclastic flows that extended 6-9km from the vents Sierra Nevada Mono Lake Active Fumaroles

  23. Caldera forming eruption in Long Valley • Was 700,000 years ago • Produced 600km3 of magma • Earlier eruptions- ejected ~0.2km3 of magma (Long Valley) • Comparable to Mt. St. Helens which erupted on May 18, 1980

  24. Mt. St. Helens

  25. Mt. St. Helens in all its glory… May 18, 1980

  26. Conclusions • Long lived silicic magma chamber beneath Long Valley • A smaller magma chamber beneath Inyo/Mono Craters • Eruptions may be preceded by multiple episodes of unrest

  27. This can be separated by decades of quiet • Most likely, the Inyo/Mono Crater chain will produce the next large eruption • Inyo/Mono last erupted 500-600 years ago…and it erupts every 500 years…is it due again?

  28. An eruption from either system though will be preceded by accelerated levels of unrest • There should be ample warning • A large earthquake in the area however, could set the whole system off

  29. View from on top Mammoth Mountain Horseshoe Lake Area where trees were killed recently by high levels of carbon dioxide gas in the soil

More Related