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Monthly Update
Monday, February 01, 2016 10:17 AM
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

CalVO Fact Sheet Published En Español
January 01, 2016

We are pleased to announce the Spanish translation of our recently published CalVO Fact Sheet The California Volcano Observatory – Monitoring the State's Restless Volcanoes.

Estamos muy contentos de compartir un folleto recientemente publicado por el Observatorio de Volcanes de California (CalVO) en Menlo Park, California, que ya está disponible en Español.

The Spanish version, El Observatorio Volcánico de California (CalVO) – Vigilando los Volcanes Activos del Estado, provides information about how the USGS Volcano Hazards Program monitors, researches, and provides hazards information about volcanoes in California.

Follow the links to download your own copy.

New insight into faults in the Long Valley Caldera reduces the predicted earthquake shaking intensity
December 22, 2015

The shaking hazard posed by earthquakes on range-front faults near the town of Mammoth Lakes, CA is lower than previously estimated. A re-evaluation of geologic and geophysical data in Long Valley Caldera shows that two large Basin and Range faults (Hartley Springs and Hilton Creek) do not extend into the caldera, as previously thought. According to a Uniform California Earthquake Rupture Forecast based upon 2008 data, these two major Basin and Range faults are capable of producing magnitude 6.5 or greater earthquakes in the Long Valley volcanic region. However, recent CalVO research published in the Bulletin of the Seismological Society of America provides evidence that neither fault has ruptured within the caldera since its formation some 760,000 years ago. Earthquakes that do occur in the caldera are much smaller in magnitude, most likely caused by minor faults as well as ongoing volcanic resurgence.

The research by Dave Hill, Scientist Emeritus and former Scientist-in-Charge of the Long Valley Observatory (now CalVO), and Emily Montgomery-Brown, Research Geophysicist at CalVO, is the scientific basis for a new appendix to the scenario earthquake hazard report, which reduces the potential shaking hazard in the vicinity of Mammoth Lakes and Long Valley caldera. Evidence indicates that rupture along the Hartley Springs and Hilton Creek faults both end at the rim of the Long Valley Caldera. In the case of the Harley Springs fault, however, extension continues into the caldera, but it is driven by dike emplacement related to the Inyo Domes volcanic chain ("the Inyo Dike").

Those of us who love the Mammoth Lakes area are somewhat relieved to know that although it is still a geologically exciting and active place, Mammoth is slightly safer from earthquakes than previously predicted!

New study reveals California's Big Pine Volcanic Field is younger than previously recognized
December 01, 2015

California's Big Pine Volcanic Field is much younger than scientists previously thought, posing new considerations for volcanic hazards in the region. The volcanic field lies along the US Route 395 corridor of the eastern Sierra near the Owens River, a major source of water for Los Angeles. A new study by USGS geologist Jorge Vazquez reveals that the most recent basaltic lava-flow and cinder-cone eruptions occurred approximately 17,000 years ago. That may not sound so young, but it implies that there could still be a pathway for magma to fuel similar types of eruptions from the region in the future. Although the Big Pine Volcanic Field was not considered in the 2005 threat ranking of US volcanoes, understanding the volcanic history is important for reducing the risk from future hazards in the area.

USGS scientist Jorge Vazquez and his colleagues used field mapping and cosmogenic chlorine dating techniques to improve understanding of the timing of the most recent volcanic eruptions near Aberdeen, CA, a small town between Big Pine and Independence. Results from the study indicate eruptions at about 17, 27 and 40 thousand years ago.

Field-trip guide for Lassen Volcanic Center published
November 16, 2015
USGS geologists Patrick Muffler and Michael Clynne published a new geologic field-trip guide for areas in and around Lassen Volcanic National Park in northern California. The guide begins with a comprehensive overview of the geologic framework and the stratigraphic terminology of the Lassen region, based primarily on the "Geologic map of Lassen Volcanic National Park and vicinity". The geologic overview is followed by detailed road logs describing the volcanic features that can easily be seen in the park and its periphery. Twenty-one designated stops provide detailed explanations of important volcanic features. The guide also includes mileage logs along the highways leading into the park from the major nearby communities. The field-trip guide is intended to be a flexible document that can be adapted to the needs of a visitor approaching the park from any direction. Try it out on your next vacation!