"Newberry volcano, situated east of the Cascade Range, is one of the largest volcanoes in the conterminous United States, covering an area of about 1600 sq km. The low-angle basaltic to basaltic-andesite shield volcano is dotted with more than 400 cinder cones; however Newberry has also produced major silicic eruptions associated with formation of a 6 x 8 km wide summit caldera containing two caldera lakes. The earliest eruptive products (<0.73 million years ago) (Ma) consist of a sequence of ash-flow and airfall tuffs. Caldera collapse is thought to be associated with major ash flows emplaced about 0.5 and 0.3-0.5 Ma. these eruptions were preceded by the emplacement of numerous mafic cones and vents and silicic lava domes and flows, many of which are aligned NNW and NNE parallel to regional fault zones. A rhyolitic magma chamber has been present throughout the Holocene. Six major eruptive episodes from the early Holocene to about 1300 years ago have included both the eruption of basaltic lava flows from flank vents and the explosive ejection of rhyolitic pumice and pyroclastic flows and the extrusion of obsidian flows within the caldera."  -Smithsonian Volcano Archive
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