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Lava Butte
Lava Butte is a cinder cone located in central Oregon, USA, just west of US Highway 97 between the towns of Bend, Oregon, and Sunriver, Oregon. It is part of a system of small cinder cones on the northwest flank of Newberry Volcano, a massive shield volcano which rises to the southeast. The cinder cone is capped by a crater which extends about deep beneath its south rim, and deep from the summit on its north side. Lava Butte is part of the Newberry National Volcanic Monument.
== Volcanic history ==
Like the other cinder cones in the area, Lava Butte only experienced a single eruption, dated by geologists in 1977 to 6,150 carbon-14 years, equivalent to about 7,000 years ago. The eruption began with a fissure spewing hot cinders to form the cone. In the next phase, a river of hot basalt flowed from the base of the small volcano to cover a large area to the west with a lava flow which remains largely free of vegetation. The lava flows reached the Deschutes River about to the west of the cone, burying its former channel under over of lava and damming the river to form a lake, known as Lake Benham. The river eventually overflowed the lava dam and eroded down into it, draining the lake and forming Benham Falls. Geologists estimate that 90% of the magma erupted as lava flows, 9% as scoria which forms the cone, and 1% as volcanic ash which forms a thin layer extending to the north.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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