10/26/2024
All volcanoes in California were at normal background levels of activity last week. https://www.usgs.gov/programs/VHP/volcano-updates (Scroll down for summary)
Why are there lava domes next to the Salton Sea? The answer lies in the unique tectonics of the location. The Salton Sea geothermal field, where the five Salton Buttes lava domes are located, lies in the Salton Trough, the landward extension of the Gulf of California. This is an area of active crustal spreading as well as an example of a "leaky" transform fault - a place where magma is able to rise through fault zones, namely the Brawley and Imperial zones. We know this because the rhyolitic lava domes contain many xenoliths (inclusions) of rock related to the tectonics beneath them: tholeitic basalt similar to oceanic basalts found in active spreading centers; sediments metamorphosed by underlying geothermal activity; and granophyre, or granitic rock derived from remelting of juvenile mafic crust from the spreading center. The granitic xenoliths are, in fact, some of the youngest granitic rocks on Earth, at about 20,000 years, and the rhyolitic domes are result of these granitic melts reaching the surface through the fault zones.
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Recent observations: Earthquakes >M1 were observed at the Coso Volcanic Field, and Salton Buttes. Typical moderate levels of seismicity were present in The Geysers south of Clear Lake and in the Sierra Nevada range south of the Long Valley Caldera.
