Brokeoff Mountain
| Mount Tehama Brokeoff Mountain/Volcano |
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|---|---|
Broken northeast face of Mount Tehama.
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| Highest point | |
| Elevation | 9,239 ft (2,816 m) NAVD 88 |
| Prominence | 915 ft (279 m) |
| Listing | California county high points 17th |
| Coordinates | 40°26′44″N 121°33′34″W / 40.4454368°N 121.5594258°WCoordinates: 40°26′44″N 121°33′34″W / 40.4454368°N 121.5594258°W |
| Geography | |
| Location | Shasta / Tehama counties, California, U.S. |
| Parent range | Cascade Range |
| Topo map | USGS Lassen Peak |
| Geology | |
| Mountain type | Eroded stratovolcano |
| Volcanic arc | Cascade Volcanic Arc |
| Climbing | |
| Easiest route | Hike |
Mount Tehama (also called Brokeoff Volcano or Brokeoff Mountain) is an eroded andesitic stratovolcano in the Cascade Volcanic Arc and the Cascade Range in Northern California. Part of the Lassen volcanic area, its highest remaining remnant, Brokeoff Mountain, is itself the second highest peak in Lassen Volcanic National Park and connects to the park's highest point, Lassen Peak. Located on the border of Tehama County and Shasta County, Tehama's peak is the highest point in the former. The hikers that summit this mountain each year are treated to "exceptional" views of Lassen Peak, the Central Valley of California, and many of the park's other features. On clear days, Mount Shasta can also be seen in the distance.
Tehama started life some 600,000 years ago. At its peak activity, it reached approximately 3,350 meters (11,000 ft) high, with a basal diameter of approximately 12 kilometers. Volcanic activity then declined 400,000 years ago, with other volcanic lava domes forming at the edges of Mount Tehama later on, the largest and best known of which is Lassen Peak. A combination of continued hydrothermal activity and erosion, particularly by glaciers during ice ages, removed the central cone of the volcano, leaving a large caldera, the northern edge of which can still be seen.
Other remnants of Mount Tehama include Mount Conard, Pilot Pinnacle, Mount Diller, and Diamond Peak.
The area near Lassen Peak became a haven for new settlers throughout the 1800s. Wagon trains followed winding trails on the Nobles Emigrant Trail which cut through the Lassen Peak vicinity near Sacramento Valley. One of the main landmarks along this trail was a volcano. Called Lassen Peak after Peter Lassen, a prominent blacksmith and guide who escorted California settlers, the volcano and the area around it were given merit for their gripping volcanic phenomena, which included lava beds and extinct volcanic cones. In May 1907, Lassen Peak was declared a National Monument by President Theodore Roosevelt to protect the area for "future generations to study and enjoy". Roosevelt had been told that the area was actually extinct in terms of eruptive activity. Despite assurance from Native Americans in the area that the mountain was indeed active, settlers continued to think that Lassen Peak was extinct and "dead" and so continued to settle nearby. The natives continued to declare that "one day the mountain would blow itself to pieces". In May 1914, almost exactly seven years later, the volcano began a large explosive eruption sequence. More than a hundred eruptions of varying size took place over the next seven years, attracting national interest and the designation of national park in 1916.
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