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|Advisories / Alerts|
Monitored CALIFORNIA VOLCANOES
Current Volcano Alert Level: all NORMAL
Current Aviation Color Code: all GREEN
Activity Update: All volcanoes monitored by CalVO's telemetered, real-time sensor networks exhibit normal levels of background seismicity and deformation. Real-time monitoring networks are in place at Mount Shasta, Medicine Lake Volcano, Clear Lake Volcanic Field, Lassen Volcanic Center, Long Valley Caldera and Mono-Inyo Chain.
Observations for April 1, 2013 (0000h PT) through April 30, 2013 (2359h PT):
Mt Shasta: No earthquakes were detected.
Medicine Lake: One M=1.1 earthquake was detected.
Lassen Volcanic Center: Five earthquakes were detected, all of which were below magnitude 2.0.
Clear Lake Volcanic Field: Eight earthquakes were detected (all less than magnitude 2.0). [Note: Typical high level of seismicity was observed under the Geysers steam field located at the western margin of CLVF. The largest event was M=3.4].
Long Valley Caldera and Mono-Inyo Chain: Thirteen earthquakes were located in the southern part of Long Valley Caldera (all were below magnitude 2.0 ); One M=2.6 earthquake was located on the Mono-Inyo chain near June Lakes. Five earthquakes were detected under Mammoth Mountain (all magnitudes under 2.0) [Note: The typical high level of seismicity was observed south of the caldera in the Sierra Nevada range. The largest event was M=2.4]
The U.S. Geological Survey will continue to monitor these volcanoes closely and will issue additional updates and changes in alert level as warranted. For a definition of alert levels see http://volcanoes.usgs.gov/activity/alertsystem/icons.php.
As 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. For additional USGS CalVO volcano information, background, images, and other graphics visit http://volcano.wr.usgs.gov/vsc/observatories/calvo.html. For general information on the USGS Volcano Hazard Program http://volcanoes.usgs.gov. Statewide seismic information for California and Nevada can be found at http://earthquake.usgs.gov/earthquakes/recenteqscanv/.
CalVO Alert Archive Search
|Much of the Long Valley area of eastern California is covered by rocks formed during volcanic eruptions in the past 2 million years. A cataclysmic eruption 760,000 years ago formed Long Valley Caldera and ejected flows of hot glowing ash, which cooled to form the Bishop Tuff. Wind-blown ash from that ancient eruption covered most of the Western United States (inset). This massive eruption was followed by hundreds of smaller eruptions over the next few hundred thousand years. These eruptions of lava flows, domes, and pyroclastic flows were concentrated in the central and western parts of the caldera (green and yellow areas). Mammoth Mountain was built eruptions between about 200,000 and 50,000 years ago. Volcanic activity then moved northward to the Mono Lake area about 35,000 years ago to build the Mono Craters. The most recent eruptions in the area occurred from the Mono and Inyo Craters about 600 years ago, and from Negit Island in Mono Lake about 250 years ago.|
|Map showing topographic outline of Mammoth Mountain along the southwestern edge of Long Valley Caldera, phreatic craters (pits) formed about 700 years ago in response to shallow intrusions of magma, Mammoth Mountain fumarole (MMF), and areas of tree kill related to high concentrations of carbon dioxide in soil gas. The tree-kill areas shown totaled about 170 acres in 1995. Also shown are two vaults that access buried water lines (for snow making) where CO2 concentrations in excess of 95 percent have been measured.|
|Source: Long Valley Observatory|
California-Nevada Fault Map for Long Valley
California-Nevada Fault Map for Long Valley unavailable, please try later.
Earthquake list for map of Long Valley
|Long Valley Volcano unavailable, please try later.|