Scientists at the volcano observatories of the U.S. Geological Survey pay close attention to volcanoes of the Cascade Range, Alaskan Peninsula and Aleutian Arc. These areas have young and frequent volcanic eruptions, form conspicuous large edifices, and can produce high-silica magmas that are sometimes very explosive. These volcanoes threaten life and property, even including jet aircraft that might fly over them.
A different group of volcanoes are located to the east of the Cascade Range from northern California to central Oregon. In this region, the extensional tectonics of the Basin-and-Range province impinge on the subduction process that created the Cascade Range. These "rear-arc" volcanoes are not explosive, but instead erupt fluid magmas, akin to Hawaiian basalts, at intervals of 10s to 100s of thousands of years. Their high effusion rates produce eruptions that can inundate scores of km2 in just months to years with volumes 6 to 8 km3of lava. The broad lava flow fields from these eruptions are gently inclined, and fill the topographic basins between older, eroded volcanoes. Through time, the basins are covered by sediments, and form marshy, and grassy meadows in the dry environments of northern California and central Oregon. Because the basalt lava in these flows shrinks upon cooling and forms cracks, they hold and convey groundwater from zones of higher rainfall to areas that are semi-arid. This abundant groundwater resource is very important to the economy of NE California and central Oregon.
Scientists at the California Volcano Observatory are studying an interesting aspect of 3 of these voluminous rear-arc basalt eruptions around 300,000 years ago. While rear-arc eruptions are usually separated in time, these 3 eruptions share nearly identical whole-rock chemistry values, and have identical characteristic remanent magnetic directions, "locked in" when they erupted and cooled. This suggests that all 3 eruptions occurred in no more than a century or two. Vents for the Tennant and Dry Lake basalt fields are only 9 km apart, separated by a ridge of older volcanic rocks, whereas the vent for the Hammond Crossing basalt field is farther SSE and 56 km from the Dry Lake vent. The dike(s) that fed the common eruptive episode which created these lava fields may have been very long, breaking the surface at very separate locations. The study's authors are examining other, older voluminous rear-arc lava fields to see if additional, common eruptive episodes can be identified.
The Mono Craters, a line of volcanic domes and craters south of Mono Lake in eastern California, represent the youngest rhyolitic volcanoes in the western United States. Rhyolite is a magma that is viscous and prone to explosive eruption. Consequently, these volcanoes pose a significant volcanic hazard to the region. Volcanic ash from past eruptions of Mono Craters covered large areas of California, and fell as far as Utah and Nevada. Up to now, the chronology of volcanism at Mono Craters has only been partly understood. The timing of the youngest eruptions has been known from carbon-14 dating of plants that were buried by ash; however, the chronology of the older eruptions has been uncertain.
A new study using tiny mineral crystals and the radioactive-decay series of uranium has revealed the early eruption history of Mono Craters. Marcaida et al. (2019) used an ion-shooting mass spectrometer to measure uranium and its daughter isotopes in zircon and allanite crystals in the rhyolites, and calculated the ages of their crystallization immediately before eruption. The results reveal that about 20 eruptions occurred between 10,000 and 65,000 years ago. In addition, the researchers used the new data to correlate ash beds around Mono Lake to their source volcanoes, and were able to identify ash expelled by explosive eruptions at nearby Mammoth Mountain.
Marcaida et al., 2019, Constraining the early eruptive history of the Mono Craters rhyolites, California, based on 238U–230Th isochron dating of their explosive and effusive products: Geochemistry, Geophysics, Geosystems. https://doi.org/10.1029/2018GC008052
The potential for damaging earthquakes, landslides, floods, tsunamis, and wildfires is widely recognized in California. The same cannot be said for volcanic hazards, despite the fact that eruptions occur in the state about as frequently as the largest earthquakes on the San Andreas Fault in San Francisco. At least ten volcanic eruptions have taken place in California in the past 1,000 years—most recent is the Lassen Peak eruption of 1914 to 1917 in Northern California—and future volcanic eruptions are inevitable. Based on the record of volcanism over the last few millennia, the likelihood of another eruption occurring in California in the next 30 years is about 16 percent.
A new 2019 report, "California's Exposure to Volcanic Hazards", prepared in collaboration with the State of California Governor's Office of Emergency Services (CalOES) and the California Geological Survey (CGS), provides a broad perspective on the State's exposure to volcanic hazards by integrating volcanic hazard information with geospatial data on at-risk populations, infrastructure, and resources. The information in this report is intended to prompt follow-up site and sector specific vulnerability analysis and improved hazard mitigation, disaster planning, and response protocols.
Read the report here: https://pubs.er.usgs.gov/publication/sir20185159
During a tour of western USGS offices, Director James F. Reilly II visited the CalVO offices and operations center in Menlo Park, CA. After meeting early-career scientists and conducting a town hall on the Menlo Park Campus, Director Reilly visited the CalVO Operations room, where he received updates on CalVO's ongoing work with stakeholders in California, the observatory's role in volcanic crisis response (particularly in the 2018 Kilauea eruption), and new efforts to produce long-term hazard assessments that will support land management and emergency planning operations in the State. He also toured the Magma Dynamics Lab, and heard how samples of molten magma are created in special furnaces and pressurized vessels to simulate the physical and chemical processes that precede hazardous volcanic activity.
Director Reilly was confirmed for the USGS Director's position in April 2018. He is the 17th USGS director, and has a background in geological exploration research, space operations, and academic management. He had a 13-year career as an astronaut at NASA, where he flew 3 spaceflight missions and 5 spacewalks, and his geological research has taken him to Antarctica and the depths of the continental slope in the Gulf of Mexico.
A new USGS report, Science for a Risky World: A USGS Plan for Risk Research and Applications, defines for the first time the role of USGS in risk research and applications. This includes hazard assessments, operational forecasts and warnings, vulnerability assessments, risk assessments, risk communication, decision-support systems, and post-event assessments. These activities and products are connected by the need to directly support decision makers in their efforts to better understand societal risk from hazards and to have the necessary information to make science-based, risk reduction decisions. The Risk Plan identifies the Bureau's core competencies in this arena and includes background on and specific recommendations for building institutional capacity for creating sustained partnerships, supporting professional staff, and improving product delivery.
Since 1980, there have been 120 eruptions and 52 episodes of notable volcanic unrest at 44 U.S. volcanoes. When erupting, all volcanoes pose a degree of risk to people and infrastructure. However, the risks are not equivalent from one volcano to another because of differences in eruptive style and geographic location.
The USGS assesses active and potentially active volcanoes in the U.S., focusing on history, hazards and the exposure of people, property and infrastructure to harm during the next eruption. The assessment uses 24 factors to obtain a score and threat ranking. The findings are in the newly published 2018 Update to the U.S. Geological Survey National Volcanic Threat Assessment.
Three of the eighteen very high threat volcanoes are in California (Mount Shasta, Lassen and Long Valley) where explosive and snow- and ice-covered volcanoes can project ash or lahar (debris flow) hazards long distances to densely populated and highly developed areas.
The threat ranking is not a list of which volcano will erupt next. Rather, it indicates how severe the impacts might be from future eruptions at any given volcano. The volcanic threat assessment helps prioritize U.S. volcanoes for research, hazard assessment, emergency planning, and volcano monitoring.
Subscribe to the Volcano Notification Service for customized emails about volcanic activity at U.S. monitored volcanoes.
The repetitive timing of this volcanic activity poses some interesting questions about hazards. The Lake Tahoe area is not currently considered to be volcanically active (it must have had an eruption in the last 10,000 years to meet that criteria). However, if magma were to return to the area, future eruptions and new lava dams would pose a flooding hazard both around the Lake Tahoe basin and beyond. Lava dams are known to fail rapidly, and a dam that raised the level of the lake and then collapsed could cause serious flooding downstream along the Truckee River. For now, however, there is no danger of an eruption, and such an event might be hundreds of thousands or even millions of years in the future - or might never occur at all.
Kortemeirer, W., Calvert, A., Moore, J.G., Schweickert, R., 2018, Pleistocene volcanism and shifting shorelines at Lake Tahoe, California: Geosphere, vol. 14, no. 2, 23 p. doi: 10.1130/GES01551.1.
The course is designed to give a primer on volcanic hazards and how the USGS monitors volcanoes and communicates in a crisis, but also devotes ample time to a tabletop eruption scenario where emergency managers are led through a fictional volcanic crisis and discuss how they would respond to escalating volcanic activity. The two-day course addresses the scientific, communication, managerial, and psychological aspects of volcanic crises, and allows insight into the goals of different groups in responding to volcanic hazards. CalVO scientists will conduct a similar training at Lassen Volcanic National Park in January 2018.
California is well-known for its frequent earth
Several new and updated field guides for the 2017 Scientific Assembly of the International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) in Portland, Oregon showcase California's volcanoes. Upcoming publications for Medicine Lake, Mount Shasta, Lassen Peak, Long Valley and Mammoth Mountain will provide easy to follow and informative field trips. The new collection of guidebooks can be found at the USGS Publications Warehouse and summarizes decades of advances in understanding volcanic and tectonic processes of western North America.
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.
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.
Three jolting earthquakes occurred in the wee hours this morning near Hawthorne NV, with two M5.7 events and a M5.5 occurring between the hours of 12:18 AM PST and 1:13 AM PST. The earthquakes are related to movement along a NW striking regional fault zone known as the Walker Lane. As of this writing there have been 135 aftershocks, most in the M1-2 range. A similar sequence of earthquakes in April-May 2011 known as the "Hawthorne earthquake swarm" occurred in the same general area.
Although the earthquakes are near Nevada's Aurora-Bodie Volcanic Field (see map), the events are unlikely to be related to volcanic unrest. The lavas of Aurora-Bodie Volcanic Field look "young" but the most recent eruption was 110,000 years ago. The field has a history of eruptions that date as far back as 3.6 million years ago.
More information on the earthquake activity can be found on the University of Nevada, Reno website: http://www.seismo.unr.edu/Earthquake
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.
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.
Volcanologists from volcano observatories around the world met at the international Volcano Observatory Best Practices Workshop in Vancouver, Washington from November 15-18th to collaborate on how to best communicate volcanic hazard and risk via long-term assessments. Volcanic hazards are a threat to millions of people who live near the world's 1,550 active volcanoes. Together as a global community of volcanologists we shared ideas, success stories, and useful strategies that are critical to protecting peoples' lives and communities' livelihoods.
An overarching discovery during the meeting was that many best practices are tailored to specific countries and volcanoes, since observatories have variable resources and community involvement. As a result, a variety of hazard assessment approaches were featured, including numerical models and complex databases, user-tailored hazard maps, and new communications strategies and tools—including how to represent long-term volcanic hazards on maps.
CalVO scientists contributed their own thoughts on developing the "next generation" of hazard assessments for US volcanoes, a process that has already begun with updating and revised hazard assessments and maps. The Lassen Volcanic Center assessment (2012) and its accompanying map are the newest of these products to be released for California volcanoes.
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.