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The geology of the Lassen volcanic area in the U.S. presents a record of sedimentation and volcanic activity in and around Lassen Volcanic National Park in Northern California. Heat from the subduction of tectonic plates has fed scores of volcanoes over at least the past 30 million years, including those in the Lassen volcanic area. Lava flowed over a lahar-based formation to create the lava plateau that the park sits on. About 600,000 years ago, Mount Tehama started to rise in the park's southwest corner. Roughly 27,000 years ago, a lava dome pushed through Tehama's former flank, becoming Lassen Peak. Phreatic (steam-blast) eruptions, lava flows, and cinder cone formations have persisted into modern times, particularly the formation of Cinder Cone and the 1914 to 1921 eruptions of Lassen Peak (eruption pictured). Since the latter eruptions, the only volcanic activity has been from mud pots and fumaroles. Renewed vigorous volcanic activity could threaten life and property in the area. (Full article...)
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