Long Valley Volcano

Long Valley Volcano - Current Update

U.S. Geological Survey
Tuesday, September 3, 2019, 10:45 AM PDT (Tuesday, September 3, 2019, 17:45 UTC)

Current Volcano Alert Level: all NORMAL
Current Aviation Color Code: all GREEN

Activity Update: All volcanoes monitored by CalVO using telemetered, real-time sensor networks exhibit normal levels of background seismicity and deformation. Volcanoes monitored include Mount Shasta, Medicine Lake Volcano, Clear Lake Volcanic Field, Lassen Volcanic Center, Long Valley Volcanic Region, Coso Volcanic Field, Ubehebe Craters, and Salton Buttes.

Observations for August 1, 2019 (0000h PST) through August 31, 2019 (2359h PST):
Mt Shasta: Three earthquakes at or above M1.0 were detected, the largest of which was M1.79.
Medicine Lake: One earthquake at or above M1.0 was detected (M1.20).
Lassen Volcanic Center: Two earthquakes at or above M1.0 were detected, the largest of which was M1.40.
Clear Lake Volcanic Field: Two earthquakes were detected registering M1.0 or greater. The largest event was M1.04. [Note: The typical high level of seismicity was observed under the Geysers steam field located at the western margin of CLVF. The largest event was M2.75].
Long Valley Volcanic Region: In Long Valley Caldera, 100 earthquakes of M1.0 or greater were detected, with the largest registering M2.92. Many of these earthquakes were associated with several minor seismic swarms that occurred on August 23-24, ~2-7 km east of Mammoth Lakes. Two earthquakes at or above M1.0 were detected in the Mono Craters region, with the largest registering M1.58. No earthquakes at or above M1.0 were detected under Mammoth Mountain. [Note: The typical high level of seismicity was observed south of the caldera in the Sierra Nevada range, with the largest registering M2.67.]
Ubehebe Craters: No earthquakes at or above M1.0 were detected.
Salton Buttes: Nine earthquakes were detected registering M1.0 or greater. The largest was M1.84.
Coso Volcanic Field: 1116 earthquakes of M1.0 or greater were detected, with the largest registering M5.01. Many of these events were associated with a seismic swarm that occurred on August 22-23 at the southern margin of Coso Volcanic Field. Recent elevated seismicity in the region is described in CalVO Information Statements and at https://volcanoes.usgs.gov/observatories/calvo/.

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://volcanoes.usgs.gov/observatories/calvo/. 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/.

Simplified Long Valley Caldera Geologic Map

Simplified Long Valley Caldera Geologic MapMuch 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.

Tree Kill Maps of Long Valley Caldera and Mono-Inyo Craters Volcanic Chain, California

Tree Kill Maps of Long Valley Caldera and Mono-Inyo Craters Volcanic Chain, CaliforniaMap 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

DustCam at Mono Lake, California

Mono Lake DustCam (click for enlarge)
DustCam View (click for enlarge)
Mono Lake , California, USA DustCam View:
Mono Lake also violates the federal PM-10 standard. The State Water Resources Control Board considered this in setting the required Mono Lake level in 1994. The District´s Mono Basin SIP was approved by the State in 1995 and sent to the EPA. The lake has risen about 10 feet since the mid-90s and PM-10 levels at some sites have decreased. The lake level needs to raise approximately nine more feet in order to sufficiently control PM-10 emissions.

Mammoth Lakes has high levels of PM-10 in the winter due to a combination of wood smoke and cinders put on icy roads for traction during the winter. In cooperation with the District, the Town developed an ordinance in 1990 to control both sources. The Mammoth Lakes SIP was submitted to the federal government and it has been approved. Since implementation of the ordinance, PM-10 levels have dropped significantly.

DustCam image courtesy of ...

Information courtesy of ... U.S. Geological Survey
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