Explore Geology
geology fieldnotes title

Lassen Volcanic

National Park


cover of park brochure

park geology subheading
Sunset at Lassen Volcanic National Park
Lassen Volcanic National Park, California

The Mountain Reawakens
In May 1914 Lassen Peak burst into eruption, beginning a seven-year cycle of sporadic volcanic outbursts. The climax of this episode took place in 1915, when the peak blew an enormous mushroom cloud some seven miles into the stratosphere. The reawakening of this volcano, which began as a vent on a larger extinct volcano known as Tehama, profoundly altered the surrounding landscape.

The area was made a National Park in 1916 because of its significance as an active volcanic landscape. The park is a compact laboratory of volcanic phenomena and associated thermal features (except true geysers). It is part of a vast geographic unit - a great lava plateau with isolated volcanic peaks - that also encompasses Lava Beds National Monument, California, and Crater Lake National Park, Oregon.

Before the 1980 eruption of Mount Saint Helens in Washington, Lassen Peak was the most recent volcanic outburst in the contiguous 48 states. The peak is the southernmost volcano in the Cascade Range, which extends from here into Canada. The western part of the park features great lava pinnacles (huge mountains created by lava flows), jagged craters, and steaming sulphur vents. It is cut by spectacular glaciated canyons and is dotted and threaded by lakes and rushing clear streams. Snowbanks persist year-round and beautiful meadows are spread with wildflowers in spring. The eastern part of the park is a vast lava plateau more than one mile above sea level. Here are found small cinder cones (Fairfield Peak, Hat Mountain, and Crater Butte). Forested with pine and fir, this area is studded with small lakes, but it boasts few streams. Warner Valley, marking the southern edge of the Lassen Plateau, features hot spring areas (Boiling Springs Lake, Devils Kitchen, and Terminal Geyser). This forested, steep valley also has gorgeous large meadows.

The 1980 eruption of Mount Saint Helens reduced Lassen's superlative status, but it increased the park's significance as an over 70-year laboratory of possible recovery patterns for Mount Saint Helens. The Devastated Area evidences the combined mud flow and gas blast destruction typical of many volcanic eruptions in the Cascades. The Chaos Jumbles area looks similarly destroyed, but for a different reason. An air-cushioned avalanche - one that fell so rapidly en masse that it trapped and compressed air beneath itself - crashed down the Chaos Crags about 300 years ago. The air acted as a lubricant, enabling the avalanche to rush across the valley at more than 100 miles per hour. It pushed 400 feet up the side of Table Mountain, before losing its momentum and surging back down across Manzanita Creek.

Lassen geothermal area - Sulphur Works, Bumpass Hell (largest), Little Hot Springs Valley, Boiling Springs Lake, Devils Kitchen, and Terminal Geyser - offer bubbling mud pots, steaming fumaroles, and boiling water. Some of these thermal features are getting hotter. Scientists think that Lassen Park and Mount Shasta are the most likely candidates in the Cascades to join Mount Saint Helens as active volcanoes.

The Pacific Ring of Fire and Lassen
ring of fireLassen Peak is but one of the active, dormant, or extinct volcanoes that extend around the Pacific Ocean in a great "Ring of Fire". This zone of volcanoes and earthquakes marks the edges of plates that form the Earth's crust. Volcanic and seismic disturbances occur as these great slabs override or grind past each other.>

The theory of Plate Tectonics holds that as the expanding oceanic crust is thrust beneath the continental plate margins, it penetrates deep enough into the Earth to be partly remelted. Pockets of molten rock (magma) result. These become the feeding chambers for volcanoes.

Ancestral Mount Tehama
About 600,000 years ago a great Pacific Ring of Fire stratovolcano (Mount Tehama) gradually built up here through countless eruptions. Before Lassen Peak was emplaced, Mount Tehama had collapsed, but its caldera was breached and no lake developed as did Crater Lake in Oregon. Mount Tehama's main vent was probably what is now the park's Sulphur Works. Remnants of its caldera flanks are Brokeoff Mountain, Mount Diller, Pilot Pinnacle, and Mount Conard. Connect these peaks in a circle to envision Mount Tehama's base - more than 11 miles wide.

panoramic view of Lassen Volcano

Lassen Peak
Lassen Peak began as a volcanic vent on Mount Tehama's northern flank. Considered the world's largest plug dome volcano, it rises 2,000 feet to an elevation of 10,457 feet. The park's lava came from many vents. Recent geological evidence indicates that Cinder Cone, also a volcano, erupted in the 18th century.

park maps subheading

The General park map handed out at the visitor center is available on the park's map webpage.

For information about topographic maps, geologic maps, and geologic data sets, please see the geologic maps page.

photo album subheading

A photo album for this park can be found here.

For information on other photo collections featuring National Park geology, please see the Image Sources page.

books, videos, cds subheading

Currently, we do not have a listing for a park-specific geoscience book. The park's geology may be described in regional or state geology texts.

Please visit the Geology Books and Media webpage for additional sources such as text books, theme books, CD ROMs, and technical reports.

Parks and Plates: The Geology of Our National Parks, Monuments & Seashores.
Lillie, Robert J., 2005.
W.W. Norton and Company.
ISBN 0-393-92407-6
9" x 10.75", paperback, 550 pages, full color throughout

The spectacular geology in our national parks provides the answers to many questions about the Earth. The answers can be appreciated through plate tectonics, an exciting way to understand the ongoing natural processes that sculpt our landscape. Parks and Plates is a visual and scientific voyage of discovery!

Ordering from your National Park Cooperative Associations' bookstores helps to support programs in the parks. Please visit the bookstore locator for park books and much more.

geologic research subheading

Information about the park's research program is available on the park's research webpage.

For information about permits that are required for conducting geologic research activities in National Parks, see the Permits Information page.

The NPS maintains a searchable data base of research needs that have been identified by parks.

A bibliography of geologic references is being prepared for each park through the Geologic Resources Evaluation Program (GRE). Please see the GRE website for more information and contacts.

selected links subheading

NPS Geology and Soils Partners

NRCS logoAssociation of American State Geologists
NRCS logoGeological Society of America
NRCS logoNatural Resource Conservation Service - Soils
USGS logo U.S. Geological Survey

teacher feature subheading

Currently, we do not have a listing for any park-specific geology education programs or activities.

General information about the park's education and intrepretive programs is available on the park's education webpage.

For resources and information on teaching geology using National Park examples, see the Students & Teachers pages.
updated on 01/04/2005  I   http://www.nature.nps.gov/geology/parks/lavo/index.cfm   I  Email: Webmaster
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