New research by scientists at CalVO indicates that Ubehebe Craters formed about 2100 years ago during a single eruptive event. Ubehebe Craters are a lone cluster of volcanic craters in the northern half of California's Death Valley National Park. CalVO geologists Judy Fierstein, Wes Hildreth, and Duane Champion investigated the sequence of rocks to determine whether the 15 craters formed as several independent eruptions over hundreds of years from a long-lasting, deep magma source, or whether they formed at one time.
The scientists are confident that the craters are monogenetic—created during one explosive episode when magma interacted with groundwater, over several days, weeks or months (but certainly not over hundreds of years). Their evidence: first, dozens of layers of rocks ejected during successive eruptive pulses are "conformable"—no time is represented by erosion or anything else between them, so all layers must have fallen during a short-lived eruption sequence. Second, they note that the composition of basaltic cinder samples does not vary—meaning that a single batch of magma fed the multi-crater phreatomagmatic episode. Third, measured paleomagnetic directions are almost exactly the same; again, not much time could have passed between crater-forming pulses.
Short-lived eruptive sequences like the ones that formed Ubehebe Craters are common in volcanically active areas (for example, throughout the Cascade Range). This is the only young volcano in Death Valley National Park, which was otherwise a volcanically quiet area for the last million years. The new research will be presented at the 2016 Geological Society of America Cordilleran Section meeting at the beginning of April.
Earthquakes rocked residents near the towns of Mammoth Lakes and Big Pine in eastern California this month, including a magnitude 3.74 and 3.44 on February 15 near Mammoth Lakes and another magnitude 4.8 near Big Pine on February 16. These earthquakes were related to movement along regional faults, so-called tectonic earthquakes, unrelated to volcanic unrest. CalVO scientists maintain sophisticated seismic networks, arrays of several seismometers, that detect tectonic and volcanic earthquakes around California's potentially restless volcanoes.
Continuously recorded seismic data (in addition to precise GPS data for monitoring ground deformation) is essential for identifying earthquakes related to volcanic unrest. Seismic networks located around the state's potentially active volcanoes rely on solar panels for power and complex digital technology to transmit data back to CalVO 24/7. Winter, however, presents challenges for sensor operations and data transmission. CalVO scientists often have to ski or snowmobile to preform repairs at remote monitoring stations. Network engineer John Paskievitich, from the USGS Alaska Volcano Observatory visited CalVO recently to offer his insight in keeping networks up and running through challenging winter conditions. John notes that in Alaska, "we've figured out what doesn't work for us in the digital realm, what to avoid, and what we can count on and rely on." With continually refined monitoring techniques and upgrades to the network planned for the next few years, our scientists in California will be able to assess volcanic unrest and communicate the hazards more effectively.
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.
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!