Long-Term Outlook for Volcanic Activity in Long Valley Caldera
and the Mono-Inyo Craters Volcanic Chain
The area of eastern California that includes
Long Valley Caldera and the Mono-Inyo Craters volcanic chain has a
long history of geologic
activity that includes both earthquakes and volcanic eruptions.
This activity is likely to continue long into the future. Geologic processes
proceed at a ponderous pace, however, and when measured in the time-scale
of a human lifetime, volcanic eruptions or destructive earthquakes
are infrequent events. How does this ongoing geologic activity
affect those who live in or visit this area of spectacular eastern
The best guide to the future behavior of a volcano
or volcanic system is its past behavior. Geological studies of Long
Valley Caldera and the Mono-Inyo Craters volcanic chain indicate that:
- Future eruptions are more likely to
occur somewhere along the Mono-Inyo Craters volcanic chain than
from the resurgent dome or south moat area within the caldera.
- In the absence of unrest (earthquake
swarms, ground deformation, gas emissions, and fumarole activity),
the odds of an eruption occurring in any given year along the chain
are one in a few hundred (comparable to the odds for a great [magnitude
8] earthquake along the San Andreas fault in coastal California).
- Unrest can temporarily increase the
odds of an eruption, depending on the nature, intensity, and
location of the unrest. Current, relatively low levels of unrest
increase the odds of an eruption only slightly.
- Future eruptions are likely to be
explosive in style but small to moderate in size
- Effusive (non-explosive), Hawaiian
style eruptions are also possible but somewhat less likely.
- The odds that a small eruption
somewhere along the chain will have a significant impact on any
specified place along the chain are roughly one in a thousand in
a given year.
- Larger eruptions are possible but less
common (and thus less likely) than smaller ones (true for
- Massive eruptions of the size that
accompanied formation of Long Valley Caldera 760,000 years ago
are extremely rare (none have occurred during the period of written
human history). Scientists see no evidence that an eruption of
such catastrophic proportions might be brewing beneath Long Valley
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U.S. Department of the Interior,
U.S. Geological Survey, Menlo Park, California, USA
Contact: Long Valley Web Team