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 tallest 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, Brokeoff'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. Brokeoff Volcano was active from 590,000 to 38 I7,000 years ago, during which period it erupted numerous flows with compositions ranging from basaltic andesite to dacite. At its peak, Brokeoff Volcano reached an estimated height of and had a basal circumference of approximately . At approximately 313,000 years ago volcanism began shifting to the northeast of Brokeoff Volcano, with volcanism currently focused around the modern Lassen Peak. Following the end of volcanism at Brokeoff Volcano, cooling magma beneath the surface continued to drive hot, highly reactive hydrothermal fluids circulating near the central vent of the volcano. These hydrothermal fluids chemically weathered the volcanic rocks near the central vent, making them particularly susceptible to physical erosion. Glaciers and streams were able to rapidly erode the hydrothermally altered rocks near the central vent, creating the deep Mill Canyon and exposing deep into the core of the ancient volcano. Many of the lava flows along the flanks of Brokeoff Volcano were not as extensively chemically weathered, resulting in the flanks of much of the volcano being preserved. Remnants of the flanks of Brokeoff Volcano include Brokeoff Mountain, Mount Conard, Pilot Pinnacle, Mount Diller, and Diamond Peak. History 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