Microscopic view of different groundmass textures in rocks. On the left, this groundmass is a good choice for argon dating, as it consists of abundant interconnected crystals. On the right, the groundmass consists predominantly of glass (black because it does not transmit cross-polarized light) and is a poor choice for argon dating.
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Microscopic view of different groundmass textures in rocks
Microscopic view of different groundmass textures in rocks. On the left, this groundmass is a good choice for argon dating, as it consists of abundant interconnected crystals. On the right, the groundmass consists predominantly of glass (black because it does not transmit cross-polarized light) and is a poor choice for argon dating.
Mass spectrometer, used to measure the ration of atoms with different masses, in the USGS laboratory at Moffett Field, California
linkA mass spectrometer is used to measure the ratio of atoms with different masses—in this case, the different isotopes of argon gas, which can be used to determine the age of a volcanic rock. Left: a side view of a mass spectrometer at the USGS Argon Geochronology Laboratory in Moffett Field, CA. Right: a close-up view of the sample chamber in this mass spectrometer.
Mass spectrometer, used to measure the ration of atoms with different masses, in the USGS laboratory at Moffett Field, California
linkA mass spectrometer is used to measure the ratio of atoms with different masses—in this case, the different isotopes of argon gas, which can be used to determine the age of a volcanic rock. Left: a side view of a mass spectrometer at the USGS Argon Geochronology Laboratory in Moffett Field, CA. Right: a close-up view of the sample chamber in this mass spectrometer.
Large spherulites in Hot Creek rhyolite lava in the Long Valley Caldera
The presence of spherulites indicates that a lava flow cooled quickly, and their mineralogy holds clues to its precise cooling history. USGS photo by Jessica Ball
The presence of spherulites indicates that a lava flow cooled quickly, and their mineralogy holds clues to its precise cooling history. USGS photo by Jessica Ball
Panoramic view of the Long Valley Caldera from its north side
This panorama of the Long Valley Caldera, looking from north to south, shows its broad central plain, post-caldera rhyolite flows and uplift on the right, and eastern Sierra Nevada in the background. USGS photo by Jessica Ball.
This panorama of the Long Valley Caldera, looking from north to south, shows its broad central plain, post-caldera rhyolite flows and uplift on the right, and eastern Sierra Nevada in the background. USGS photo by Jessica Ball.
Kyle R. Anderson
Kyle R. Anderson is a Volcano Geophysicist who works at the USGS California Volcano Observatory.
Kyle R. Anderson is a Volcano Geophysicist who works at the USGS California Volcano Observatory.
Phil Dawson at Mount Shasta
Phil Dawson, a Volcano Seismologist with the California Volcano Observatory, stands next to a volcanic rock on the flank of Mount Shasta, California.
Phil Dawson, a Volcano Seismologist with the California Volcano Observatory, stands next to a volcanic rock on the flank of Mount Shasta, California.