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.