An earthquake swarm started on 26 Sep 2016, 04:03AM PDT, and is ongoing in the Brawley Seismic Zone near the southern terminus of the San Andreas Fault and about 12 km (7.5 mi) north of Salton Buttes. The swarm does not appear to be related to volcanic activity. The USGS/Caltech Southern California Seismic Network has identified 37 events as of 9:10 AM PDT today with magnitudes ranging between M1.4 to M4.3 at 4 to 9 km depth. Two two previous swarms occurred in the area in 2009 and 2001. See the full report and updates.
A picture is worth a thousand words—USGS Post Doctoral Fellow Jared Peacock's new 3D geophysical model for the Long Valley Caldera and Mammoth Mountain reveals a subsurface marked by active hydrothermal reservoirs (hot water and fluids), bodies of partial melt (molten rock), and rock that has been pervasively altered to clay by fluids from a now extinct hydrothermal reservoir. Using magnetotelluric (MT) data, Jared located a robust hydrothermal reservoir with a source located about 4 km (2 and a half miles) under Deer Mountain. Groundwater heated in this reservoir flows upward and eastward towards the caldera's Resurgent Dome. A separate hydrothermal reservoir was identified under Mammoth Mountain at a depth of about 1 km (0.6 mi). Both reservoirs are fueled by heat emanating from small bodies of partially molten rock located more than 8 km (5 mi) below the surface. The new model verifies and improves upon the results of earlier geophysical investigations.
A newly released geologic map and U.S. Geological Survey Professional Paper, Eruptive History of Mammoth Mountain and its Mafic Periphery, California, by CalVO scientists Wes Hildreth and Judith Fierstein recount the geologic and volcanic history of the area east of the Sierra Nevada in greater detail than any previously published report. The map includes the Long Valley Caldera, Mono-Inyo chain, Mammoth Mountain and the Middle Fork canyon of the San Joaquin River, including Devils Postpile National Monument.
Geophysical unrest beneath the Mammoth Mountain volcano, and in adjacent parts of the Sierra Nevada and Long Valley Caldera, has generated some concern among residents, stakeholders, and geoscientists since at least 1980 when four magnitude-6 earthquakes shook the area. Three decades of volcano monitoring near Mammoth Mountain has documented numerous earthquake swarms, ground deformation, and emission of magmatic carbon dioxide gas . The new map and publication contribute detailed information to scientists' understanding of the eruption frequency and volcanic history of the area, which is essential for assessing the region's likely long-term future volcanic activity.
The new map and report represent a significant milestone after decades of geologic fieldwork and research. The release of the map and report coincides with the 2016 celebration of the 100th anniversary of the establishment of the National Park Service. In the month of July, staff from the USGS, Devils Postpile National Monument and Inyo National Forest have teamed up to offer outdoor educational activities for the public as the new map and report are unveiled. CalVO geologists Wes Hildreth, Judy Fierstein, and others will be hosting an interpretive talk at Minaret Vista Overlook near the monument on July 14. They will also lead an interpretive hike to the Devils Postpile formation and to nearby Rainbow Falls, both in the monument, on July 15. If you plan to visit Devils Postpile National Monument this week, be sure to check out these great opportunities to hear about the volcanic history of the area from expert geologists!
Summer has arrived, and for many CalVO scientists, so has the season of fieldwork. During the fall, winter and spring, many of California's volcanoes are covered with snow, and challenging weather conditions make fieldwork difficult and time consuming. However, from May through October, warmer weather with minimal precipitation make it easier for scientists to access most of the volcanic places that are inaccessible during the rest of the year. Plans this season include spending weeks in the Long Valley Caldera mapping the geology; traveling around the state to collect hydrothermal water samples and service volcano monitoring equipment; and climbing the flanks of many volcanoes to collect rock and gas samples.
Scientists recently returned from climbing up to about 14,000 feet of elevation to the summit of Mount Shasta where they collected gas samples and temperature data. They used vacuum-sealed glass bottles to collect the gas samples then carefully packaged the bottles and carried them down the mountain. The volcanic gas samples contained in the bottles were taken back to the lab at CalVO to be analyzed.
Each sample must have less than 1% air contamination in order for it to be a good sample to use for analysis of the volcanic gases. Fortunately, one of the samples collected had no detectable (less than 0.01%) air contamination, so it was a great sample to measure—the climb up Mount Shasta and back down again was a success! We're looking forward to other successful fieldwork throughout this season.
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!
USGS CalVO scientists have developed a new 3D conceptual model of the magma system below Mono Lake and Mono Craters in eastern California to give scientists a more detailed understanding of volcanic processes at depth. The technology used, magnetotellurics, measures slight electrical currents naturally created by the movement of ions in the Earth's magnetic field (like the Aurora Borealis, or Northern Lights). Magma chambers with liquid, melted rock, or a partially crystallized "mush," have a very low resistivity to electrical current flow.
The Mono Craters volcanic area is ranked among the nation's high threat volcanoes. Recent eruptions at Mono Craters occurred about 600 years ago at Panum Crater, and about 350 years ago on Paoha Island in the middle of Mono Lake. The accuracy and high resolution of the new three-dimensional images of the magma chambers and volcanic "plumbing" below Mono Basin give scientists a better understanding of their size, shape and where the next eruption might occur.Read the press release or the full research study.
Scientists, civil authorities, and emergency managers from Chile and the U.S. met in California to discuss the challenges of effective volcanic hazard education, response planning, hazard mitigation, and risk reduction, as part of the second Bi-national Exchange program for Volcanic Risk Reduction in the Americas.
The program focused on the Long Valley volcanic region (California, USA) and ChaitÃ©n Volcano (RegiÃ³n de los Lagos, Chile). Both of these restless volcanic systems have erupted rhyolite lava. Eruptions of rhyolite lava exhibit extremely diverse behavior, from sluggish lava flows to catastrophic explosions. The similarities in the nature of the hazards posed at Long Valley and ChaitÃ©n and the challenges of communicating with at-risk communities provide opportunities for scientists and civil authorities to learn from one another and strengthen risk reduction in their home countries. In the U.S. and Chile, participants inspected volcano monitoring networks, learned about the geologic history of volcanoes, volcanic hazards, eruption forecasting, disaster preparedness, and communications with affected communities.
The principle coordinators of the Chile-USA exchange are Dr. Margaret Mangan, Scientist-in-Charge of the USGS-California Volcano Observatory in Menlo Park, California, and Dr. Luis Lara, the Head of the Volcano Hazards Program at Servicio Nacional de GeologÃa y MinerÃa in Santiago, Chile. The program is funded by the U.S. Agency for International Development/Office of Foreign Disaster Assistance with cooperation from the USGS' Volcano Disaster Assistance Program.
2015 marks the centennial of the May 22, 1915 explosive eruption of Lassen Peak. The eruption forever altered an already dynamic landscape and led to the creation of a national park which serves as a place of discovery for curious visitors and a living laboratory for a variety of scientists.
USGS California Volcano Observatory and Lassen Volcanic National Park have teamed up to celebrate the eruption anniversary with several events to be held at the park over the Memorial Day weekend. Centennial resources and a schedule of events can be found on our 1915 eruption resource page.
CalVO is tracking an earthquake swarm that began on November 9 located at the Tehama County-Plumas County border within Lassen National Forest. The swarm is about 24 km WNW of the town of Chester and about 1 mile south of the Lassen Volcanic National Park boundary near the Twin Meadows Trail at Patricia Lake.
Since the start of the swarm about 80 earthquakes at or above magnitude M1.0 have been detected. A magnitude M3.86 earthquake at about 12:30 AM Nov 11 was the largest event to date. Preliminary analysis suggests that the earthquakes are related to regional fault motions along the northwest margin of the Walker Lane fault system. Ground deformation indicative of volcanic unrest has not been detected by nearby GPS receivers. Although the swarm poses no immediate threat, the CalVO will continue monitoring earthquake activity and keep in close communication with Lassen Volcanic National Park to learn of any changes in the Park's hydrothermal features.
We have been closely tracking an earthquake swarm in California's Long Valley Caldera, which started yesterday at around 4AM PDT (September 25, 2014). The swarm is located 7 miles east of the town of Mammoth Lakes, about a mile north of the airport. From about 4 AM on the September 25th to 11AM on September 26th there have been more than 500 earthquakes of magnitude M1.0 and above, including 8 earthquakes between M3.0 and M3.8, which were felt locally. This is one of several earthquake swarms that have occurred in the caldera this year. Despite the several felt earthquakes, this is still rather modest activity compared with the much more energetic swarms occurring in the 1980s and 1990s. We do not see any evidence for anomalous ground deformation associated with the swarm at this time. Part of the Long Valley Caldera, known as the "resurgent dome," has been uplifting at a rate of about an inch per year since late 2011, and this remains unchanged. Caldera uplift has occurred sporadically for the last few decades. The uplift rate observed since 2011 is small compared to rates observed in the 1980s and 1990s. The earthquakes themselves are small, brittle-failure (rock breaking) events. Such events are sometimes called "tectonic." The earthquakes do not result from the underground movement of magma. We can distinguish between brittle-failure earthquakes and those resulting from magma movement by the characteristics of the seismic waveforms.
The swarm events pose no immediate hazard. The USGS California Volcano Observatory will continue to closely track this activity and provide updates as appropriate.
Since 1990, high levels of carbon dioxide (CO2) in the soil have killed trees within about a 75-acre area adjacent to Horseshoe Lake on the south side of Mammoth Mountain. This CO2 migrates upwards to the surface from depth beneath the mountain. In June 2013, a new measurement array was installed by the USGS adjacent to Horseshoe Lake to continuously monitor changes in CO2 emissions over space and time. At the heart of this instrumentation is a set of atmospheric sensors mounted on a tripod tower above the ground surface. These sensors make high-frequency measurements of atmospheric CO2 concentrations and wind speeds and directions. Using the "eddy covariance" method, these measurements are then used to calculate rates of CO2 emission from land areas around the instrument tower (which change with atmospheric conditions such as wind speed and direction) on a half-hourly basis. Continuous monitoring of CO2 emissions should allow for better understanding of the relationships between changes in these emissions and variations in local weather conditions and activity (for example, seismicity) beneath Mammoth Mountain.
In the late afternoon of 17 June 2013 a flurry of earthquakes started in the Long Valley Caldera east of the town of Mammoth Lakes, California (in an area known to geologists as the south moat). The swarm produced about 100 earthquakes over 5 hours before petering out; most were too small to be felt by humans (a magnitude 3.0 was the largest). The earthquakes originated at ~ 8-7 km depths where a small volume of partially molten rock is likely to reside.
Earthquake swarms are common in this part of the caldera, especially so in the 1980s and 1990s. A particularly intense swarm in the latter half of 1997 produced 12,000 events over 7 months, including eight earthquakes in the magnitude 4.0 range. Significant ground uplift accompanied the 1997-1998 swarm resulting in ~ 10 cm of caldera inflation. Yesterday's "mini swarm" pales in comparison, and does not indicate any immediate volcanic hazard within Long Valley Volcanic Center. The plots to the right (click to enlarge) show cumulative earthquake counts in the south moat for the past year as well as the number of earthquakes that occurred during the 17 June swarm. Modest, relatively steady inflation of the resurgent dome, located in the center of Long Valley Caldera, is a feature of the last couple of years, but CalVO deformation monitoring sensors show no changes related to the recent swarm.
February 2013 marked the first year of successful volcano monitoring and preparing for possible volcanic eruption for the California Volcano Observatory (CalVO). At Long Valley Caldera, analysis of continuous GPS data over the first half of 2012 showed a modest inflationary pattern within the caldera; ground motion was directed upward and away from the caldera's center, with a maximum uplift rate between 2 and 3 cm/yr. In January of this year at Clear Lake Volcanic Field, a short-lived swarm of low-magnitude earthquakes was detected under the south flank of Mt Konocti.
CalVO also worked with other agencies this year to develop information to help people better understand and prepare for the potential for volcanic eruption. A statewide ash aviation plan was formulated in conjunction with the National Oceanic and Atmospheric Administration, Federal Aviation Administration, and the California Emergency Management Association. CalVO released the hazards assessment for Lassen Volcanic Center and helped to build an interactive exhibit at Lassen Volcanic National Park. The new exhibit, located at the Park's Loomis Museum, displays regional earthquake data and videos detailing the geologic processes that helped to form the volcanic landscape at Lassen.
Many of California's young volcanoes pose a threat to people and property. Volcanic eruptions occur in the State about as frequently as our largest San Andreas Fault Zone earthquakes: ten eruptions have occurred in California in the last 1000 years.
To better prepare for volcanic events in the State, the California Emergency Management Agency (Cal EMA), the USGS California Volcano Observatory, and the California Geological Survey are working together to produce the first ever Volcano Hazard Annex to the State Emergency Plan.
On February 12, 2013, a diverse group of state and federal stakeholders assembled at Cal EMA headquarters to discuss volcano hazards and identify State and Federal assets potentially at risk. Cal EMA's new Volcano Annex will integrate hazard and socio-economic information in a format readily accessible to decision-makers at all levels of government.
Welcome to the new USGS California Volcano Observatory website! The USGS Volcano Science Center recently restructured observatory operations to optimize volcano monitoring, eruption forecasting, and hazard mitigation efforts throughout California. The new USGS California Volcano Observatory (CalVO), headquartered in Menlo Park CA, replaces the former Long Valley Observatory (LVO), which was established in 1982 to monitor the restless Long Valley Caldera and Mono-Inyo Craters region of Eastern California.
Scientists at the five USGS volcano observatories research, monitor, and assess hazards at United States volcanoes and provide activity notifications and eruption warnings in the event of volcanic crises. The volcano monitoring responsibility of CalVO includes all potentially active volcanoes in California and Nevada. The Cascade Volcano Observatory (CVO), CalVO’s sister observatory in Vancouver, WA, oversees efforts at all potentially active volcanoes in Oregon, Washington, and Idaho. CalVO and CVO share scientific expertise, administrative staff, and equipment, ensuring a strategic and cost efficient program of volcanic hazard mitigation.
Note: The Yellowstone Volcano Observatory (YVO in Menlo Park, CA) monitors volcanoes in Montana, Wyoming, Colorado, Utah, New Mexico, and Arizona. The Alaska Volcano Observatory (AVO in Anchorage, AK) oversees Alaskan volcanoes and those within the Commonwealth of the Northern Mariana Islands. The oldest USGS volcano observatory, the Hawaiian Volcano Observatory (HVO in Hawaii National Park, HI), is responsible for the state of Hawaii and is celebrating its 100th anniversary this year.