Medicine Lake Volcano : Ask Biography

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Medicine Lake Volcano is a large shield volcano in northeastern California about 50 km (31.1 mi) northeast of Mount Shasta. The volcano is located in a zone of east-west crustal extension east of the main axis of the Cascade Volcanic Arc and the Cascade Range. The 1 km (0.6 mi) thick shield is 35 km (21.7 mi) from east to west and 45 to 50 km (28 to 31.1 mi ) from north to south, and covers more than 2000 km2 (772.2 sqmi). The underlying rock has downwarped by 0.5 km (0.3 mi) under the center of the volcano. The volcano is primarily composed of basalt and basaltic andesite lava flows, and has a 7 by (4.3 km) caldera at the center.

The Medicine Lake shield rises about 1200 m (3937 ft) above the Modoc Plateau to an elevation of 2376 m (7795.3 ft). Lavas from Medicine Lake Volcano are estimated to be at least 600 km3 (1968.5 c�mi) in volume, making Medicine Lake the largest volcano by volume in the Cascade Range (Newberry Volcano in Oregon has the second largest volume). Lava Beds National Monument lies on the northeast flank of the volcano.

Medicine Lake Volcano has been erupting off and on for half a million years. The eruptions were gentle rather than explosive like Mount St. Helens, coating the volcano's sides with flow after flow of basaltic lava. Medicine Lake is part of the old caldera, a bowl-shaped depression in the mountain. It is believed that the Medicine Lake volcano is unique, having many small magma chambers rather than one large one.