Lassen Volcanic National Park
Map SatelliteComposite volcanoes, cinder and spatter cones, domes, sulphurous hot springs, fumaroles, steam vents, lava tubes and caves, as well as volcanic bombs are among the rich variety of volcanic features found in the Park.
Lassen Peak, 3,187 meters (10,457 feet) high, is the southernmost of the volcanoes of the Cascade Range. Volcanic activity in the region dates to the Pliocene when the thick lava plateau in the Park was built up. During the epoch, Mount Tehama was formed, a cone over 3,350 meters (11,000 feet) high and some 24 kilometers (15 miles) in diameter. The summit of the cone collapsed, along a series of more or less vertical faults, leaving a caldera where, today, many of the hot springs are found. Further faulting and erosion reduced the mountain, and now Brokeoff Mountain is the highest remnant.
On the northeastern slope, Lassen Peak was being formed during the Pleistocene and Recent epochs. Chaos Crags, north of the Peak, were emplaced approximately 250 years ago; soon after their formation, steam explosions on the north dome caused the mass to collapse, producing an avalanche which formed the Chaos Jumbles. There was further activity in this section in 1851 and 1857.
The most recent activity was the eruption of Lassen in 1914 - 1917. After a year of intermittent activity, lava welled up over the northeastern and northwestern rim of the summit crater and flowed down some 300 meters (1,000 feet), melting snow which caused large mudflows into Hat and Lost Creek Valleys. Three days later, on May 22, 1915, a blast on the northeastern side devastated some 15 square kilometers (6 square miles).
Glacial features are also present here, most noticeably the glacial lakes, Helen and Emerald.
Though portions of the Park are barren, or relatively so, some 700 species of plants inhabit the area. In the lower elevations, knobcone pine, Pinus attenuata, sugar pine, Pinus lambertiana, ponderosa pine, Pinus ponderosa. and white fir, Abies concolor, dominate the forest canopy. Red fir, Abies magnifica, lodgepole pine, Pinus contorta ssp. murrayana, and Jeffrey pine, Pinus jeffreyi, are the dominants in the mid-elevations. Below the alpine zone, whitebark pine, Pinus albicaulis, and mountain hemlock, Tsuga mertensiana, are the main forest components. Chaparral, with Arctostaphylos sp., Ceanothus velutinus, and chinquapin, Chrysolepis sempervirens, occurs in extensive patches.
Aspen, Populus tremuloides, willows, Salix spp., and black cottonwood, Populus trichocarpa, are found in the wet meadows and along streamsides.
Animal life is abundant and typical of the region.
Integrity: There are roads, trails and recreational facilities in the Park. The Park was established in 1916 and, in 1972, 31,964 hectares (78,982 acres) were designated as a Wilderness Area.
Use: Present
Ref: Williams, H. 1932. Geology of the Lassen Volcanic National Park, California, Univ. Cal. Dept. Geo. Sci. Bull. v. 21, n. 9, pp. 195 - 385. Berkeley, Cal.
May 1981
Inventory of California Natural Areas
Revision © 2009 Steven Louis Hartman