Medicine Lake Volcano
| Medicine Lake Volcano | |
|---|---|
Medicine Lake volcano as seen from Lava Beds National Monument
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| Highest point | |
| Elevation | 7,921 ft (2,414 m) NAVD 88 |
| Coordinates | 41°36′39″N 121°33′13″W / 41.610956028°N 121.553635458°WCoordinates: 41°36′39″N 121°33′13″W / 41.610956028°N 121.553635458°W |
| Geography | |
| Location | Siskiyou County, California, U.S. |
| Parent range | Cascade Range |
| Topo map | USGS Medicine Lake |
| Geology | |
| Age of rock | about 500,000 years |
| Mountain type | Shield volcano |
| Volcanic arc | Cascade Volcanic Arc |
| Last eruption | 1080 ± 25 years |
| Medicine Lake | |
|---|---|
The lake with Mount Shasta in the background
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Bathymetric Map
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| Location | California |
| Coordinates | 41°34′54″N 121°35′56″W / 41.58167°N 121.59889°W |
| Basin countries | United States |
| Max. length | 0.6 miles (1 km) |
| Max. width | 1.2 miles (2 km) |
| Surface area | 0.64 sq mi (1.65 km2) |
| Average depth | 24.0 feet (7.3 m) |
| Max. depth | 152 feet (46.4 m) |
| Water volume | 470,000,000 cu ft (13,400,000 m3) |
| Shore length1 | 20,384 feet (6,213 m) |
| References | |
| 1 Shore length is not a well-defined measure. | |
Medicine Lake Volcano is a large shield volcano in northeastern California about 30 miles (50 km) 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 0.6-mile (1 km) thick shield is 22 miles (35 km) from east to west and 28 to 31 miles (45 to 50 km) from north to south, and covers more than 770 square miles (2,000 km2). The underlying rock has downwarped by 0.3 miles (0.5 km) under the center of the volcano. The volcano is primarily composed of basalt and basaltic andesite lava flows, and has a 4.3-by-7.5-mile (7 by 12 km) caldera at the center.
The Medicine Lake shield rises about 3,900 feet (1,200 m) above the Modoc Plateau to an elevation of 7,795 feet (2,376 m). Lavas from Medicine Lake Volcano are estimated to be at least 140 cubic miles (600 km3) 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 active for 500,000 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.
Medicine Lake is in the caldera of the volcano, which measures 4.3 by 7.5 miles (7 by 12 km). The caldera may have formed by collapse after a large volume of andesite was erupted from vents along the caldera rim. The distribution of late vents, mostly concentrated along the rim, suggests that ring faults already existed when most of the andesite erupted. No single large eruption has been related to caldera formation. The only eruption recognized to have produced ash flow tuff occurred in late Pleistocene time, and this eruption was too small to account for formation of the caldera. Later conclusions were that Medicine Lake caldera formed by collapse in response to repeated extrusions of mostly mafic lava beginning early in the history of the volcano (perhaps in a manner similar to the formation of Kilauea caldera in Hawaii). Several small differentiated magma bodies may have been fed by and interspersed among a plexus of dikes and sills. Late Holocene andesitic to rhyolitic lavas were derived by fractionation, assimilation, and mixing from high alumina basalt parental magma. The small lake from which Medicine Lake volcano derives its name lies within the central caldera.
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Wikipedia