Mount Lassen Professional Review and Guide
"Lassen Peak, this southernmost of the Cascade volcanoes, is a minor mountain compared with the glaciated giants farther north. Its only worthwhile route is a trail leading to its summit. Mount Lassen is the significant plug-dome remnant of a former 11,000-foot stratovolcano known as Mount Tehama (or Brokeoff Volcano). Mount Tehama collapsed and was nearly erased by ice-age glaciers, but Lassen Peak, a dacite dome, extruded itself from Tehama's remains some 11,000 years ago. In May 1914, Lassen awoke, and a year later began spilling lava, snow and mud across its slopes. On May 22, 1915, the mountain erupted violently, shooting hot gasses and ash into the stratosphere. A simultaneous lateral blast and nuee ardente (hot pyroclastic flow) devastated the northwestern part of the present-day park. This eruption, and the presence of fumaroles and 200° F mud pots nearby, signal the mountain is far from dormant. Mount Lassen, the "largest plug dome in the world," is the centerpiece of one of California's less-crowded national parks, and is located in northeastern California about 180 miles north of Sacramento."