Hot springs steam in the cool morning air as dawn comes to California’s active supervolcano: Long Valley Caldera.
There are only three known caldera volcanoes in the US West big enough and young enough to still contain magma (Bailey et al.):
- Yellowstone — the one everyone has heard of.
- The Valles Caldera that we recently explored.
- Long Valley:
- USGS page.
- Current status (September 25, 2022): Normal/Green with a few small earthquakes.
Have you ever wondered where that alert system came from? As I understand the history, it developed out of a crisis at Long Valley that began in the early 1980s. Hill et al. describe what happened as part of their remarkably jargon-free chapter on this caldera.
- The USGS report California’s Restless Giant — the Long Valley Caldera.
Per Dr. Wikipedia, there is no consensus on why Long Valley exists. It’s apparently not sitting on a hotspot, as Yellowstone is, and there no nearby subduction zone to explain the volcano.
Hill et al. simply note that (link added):
It is nestled against the western escarpment of the large graben formed by the Sierra Nevada on the west and the White Mountains on the east. This impressive eastern Sierra landscape has developed over the past three million years as a result of repeated slip on the range-front normal faults and persistent volcanism.
The western US has very complex geology anyway, and Long Valley seems to be one of the tougher challenges for geoscientists to explain.
I’m including this closeup of a few of the gorgeous columnar joints in the Owens River Gorge because the sun angle obscures them in TectoNick’s video. (Image: R. V. Fisher/GVP, CC BY-NC-ND 4.0)
Are you itching to go on a field trip into the Bishop Tuff, sort of like the virtual one we took at Valles Caldera?
Nicholas Van Buer, associate professor at Cal Poly Pomona, did just that along some of the tuff exposed in the Owens River Gorge southeast of the caldera.
This would not have been a good place to be back in the day!
TectoNick notes on the video’s YouTube page that it is intended for college-level igneous/metamorphic petrology students, but don’t let that stop you from watching it.
He explains almost everything. As for technical terms, we discovered “resurgent dome” at Valles (as did Science!), and the few other things that might be unfamiliar, like “normal fault” and “rhyolite,” are easily looked up online, if you’re curious.
“Popcorn pumice,” people!
Also, almost at the end, at the 17-minute mark, he’s in the caldera itself, pointing out various landmarks. It’s a real nice ground-level view from an expert.
Petroglyphs carved into the tuff just north of Bishop, California, about 30 miles south of Long Valley Caldera. (Image: Stella the Giant/Shutterstock)
There’s a LOT of information available on Long Valley Caldera. For obvious reasons, this Very High Threat volcano receives much scientific attention.
But this is only a casual post, so I’m just passing along some more references that I found in a brief search at Google Scholar.
The paper by Fialko et al. looks at both Long Valley and the Socorro Magma Body, which we met last week, but it’s a steep read.
Still, it shows that research at one volcano pays dividends even on subjects that are hidden far underground!
Sources:
Bailey, R. A.; Dalrymple, G. B.; and Lanphere, M. A. 1976. Volcanism, structure, and geochronology of Long Valley Caldera, Mono County, California. Journal of Geophysical Research, 81(5): 725-744.
Fialko, Y.; Simons, M.; and Khazan, Y.
2001. Finite source modelling of magmatic unrest in Socorro, New Mexico, and Long Valley, California. Geophysical Journal International, 146(1): 191-200.
Hill, D. P.; Mangan, M. T.; and McNutt, S. R. 2017. Volcanic unrest and hazard communication in Long Valley volcanic region, California. In Observing the Volcano World (pp. 171-187). Springer, Cham. https://link.springer.com/chapter/10.1007/11157_2016_32
Mangan, M.; Ball, J.; Wood, N.: Jones, J. L.; and others. 2019. California’s exposure to volcanic hazards (No. 2018-5159). US Geological Survey. https://pubs.er.usgs.gov/publication/sir20185159
Flight To Wonder 