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Monthly Update
Thursday, June 01, 2017 2:37 PM US/Pacific
Current Volcano Alert Level: NORMAL
Current Aviation Color Code: GREEN
California Volcano Observatory's mission
As a part of the U.S. Geological Survey's Volcano Hazards Program, the California Volcano Observatory aims to advance scientific understanding of volcanic processes and lessen the harmful impacts of volcanic activity in the volcanically active areas of California and Nevada.

NEWS   (archive)
Young Volcanoes in California & Nevada1

New ages confirm that the youngest Eagle Lake volcanic rocks erupted 130-125 thousand years ago
April 03, 2017

New research on the ages of the most recent lava flows at Eagle Lake Volcanic Field, California suggest they are much older than once thought, minimizing the possibility of future eruption. USGS scientists recently released a report about the age of the youngest volcanic deposits at Eagle Lake, CA, in which they concluded that three of the most recent lava flows erupted 130, 127 and 123 thousand years ago. The scientists used stratigraphic, paleomagnetic, and 40Ar/39Ar dating techniques to measure the ages.

Eagle Lake is one of 14 sites in California that was previously identified for potential future volcanism. Originally, geologic mapping was used to interpret the ages of the youngest flows at Eagle Lake. The interpretations from mapping led scientists to believe that eruptions there might have occurred in the Holocene (last 10,000 years). However, the new precise ages show that the flows erupted over a hundred thousand years ago in the Pleistocene. Geologists tend to consider only volcanoes with Holocene-age eruptions to be young enough to potentially erupt again, therefore the likelihood of volcanism from Eagle Lake in the future is extremely low.

Knowing the age of the most recent volcanic eruptions throughout the state helps the California Volcano Observatory (CalVO) plan for, and efficiently deploy, its volcano monitoring resources to locations that have the greatest potential for activity. As a result of the new research at Eagle Lake, CalVO scientists have reconsidered its priority as a location that needs monitoring equipment.

New scientific publications about our California Volcanoes by USGS authors
March 15, 2017

Two new journal articles about California Volcanoes in the eastern part of the state, the Long Valley Caldera and Ubehebe Craters, are headed to press.

Early postcaldera rhyolite and structural resurgence at Long Valley Caldera, California by Wes Hildreth, Judy Fierstein, Andrew Calvert (CalVO, Menlo Park)

After the eruption of 650 cubic kilometers of material known as the Bishop Tuff, forming the Long Valley Caldera, another ~100 cubic kilometers erupted in batches over the next 110,000 years. The paper characterizes the geology of the post-caldera rhyolites.

Eruptive history of the Ubehebe Crater cluster, Death Valley, California by Judy Fierstein, Wes Hildreth (CalVO, Menlo Park)

The Ubehebe Crater cluster in Death Valley National Park was a quick eruption; that is, they all erupted over a short period of time rather than forming over a period of several hundred years. This study has been in our news before, because it documents, in detail, the reasons why Ubehebe Craters are not a long-lived volcanic system, changing previous scientific thinking.

Short-lived Long Valley earthquake swarm does not indicate heightened volcanic unrest.
December 14, 2016

A short-lived earthquake swarm occurred overnight under the Long Valley Caldera in eastern California about 4 km (2.5 mi) ESE of the town of Mammoths Lakes. The swarm does not appear to be related to increased volcanic unrest.

The swarm started with a M2.76 at 11:28 PM PST last night in the South Moat of Long Valley Caldera. This event was followed by a M3.87, the largest event in the swarm, about 15 minutes later. More than forty earthquakes between M1.0 to M3.17 occurred over the ensuing hour. The swarm gradually decayed in numbers of events and earthquake magnitudes over the course of the night to about 10 events of M1.0 or less per hour. Focal depths of earthquakes in the swarm cluster are between about 5-6 km (3-3.8 mi) below Route 203 just west of the junction with Route 395. Swarms of this type are common under the South Moat of Long Valley Caldera. At present, we see no indication of increased volcanic threat to the region.

View current monitoring data on the Long Valley Caldera Monitoring webpage.

CalVO Scientists Present Work at International 2016 AGU Fall Meeting
December 12, 2016

Fifteen CalVO scientists will present work this week at the 2016 American Geophysical Union Fall Meeting, held in San Francisco, California. The meeting is the largest one of its kind in the world: over 20,000 international scientists gather to discuss a wide range of topics and present their work to the Earth and space science community. Our scientists will present research that contributes to understanding volcanic hazards.

This year, CalVO scientist Tom Sisson has been selected as one of 60 new Fellows of the American Geophysical Union, an honor reserved for a small number of AGU members. Fellows are honored for scientific eminence in the Earth and space sciences, which Tom has achieved through his notable discoveries and innovative contributions to scientists' thinking about how magma systems work.

Tom's work applies the results of meticulous petrologic experiments to solve real-world issues surrounding volcano hazards; one example is his great volume of work on Mount Rainier. His work is important to the USGS Volcano Science Center for improving our understanding of volcano hazards, which benefits other volcano researchers and observatories worldwide.