Mt. Lassen
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Lassen Peak ( ), commonly referred to as Mount Lassen, is a
lava dome In volcanology, a lava dome is a circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions on ...
volcano and the southernmost
active volcano An active volcano is a volcano which is either erupting or is likely to erupt in the future. An active volcano which is not currently erupting is known as a dormant volcano. Overview Tlocene Epoch. Most volcanoes are situated on the Pacific Ri ...
in the
Cascade Range The Cascade Range or Cascades is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, ...
of the Western United States. Located in the
Shasta Cascade The Shasta Cascade region of California is located in the northeastern and north-central sections of the state bordering Oregon and Nevada, including far northern parts of the Central Valley and the Sierra Nevada mountain range. History Ind ...
region of
Northern California Northern California (colloquially known as NorCal) is a geographic and cultural region that generally comprises the northern portion of the U.S. state of California. Spanning the state's northernmost 48 counties, its main population centers incl ...
, it is part of the Cascade Volcanic Arc, which stretches from southwestern British Columbia to northern California. Lassen Peak reaches an elevation of , standing above the northern
Sacramento Valley , photo =Sacramento Riverfront.jpg , photo_caption= Sacramento , map_image=Map california central valley.jpg , map_caption= The Central Valley of California , location = California, United States , coordinates = , boundaries = Sierra Nevada (ea ...
. It supports many flora and fauna among its diverse habitats, which are subject to frequent snowfall and reach high elevations. Lassen Peak has a volume of , making it one of the largest lava domes on Earth. The volcano arose from the former northern flank of now-eroded
Mount Tehama 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 Moun ...
about 27,000 years ago, from a series of eruptions over the course of a few years. The mountain has been significantly eroded by glaciers over the last 25,000 years, and is now covered in talus deposits. On May 22, 1915, a powerful
explosive eruption In volcanology, an explosive eruption is a volcanic eruption of the most violent type. A notable example is the 1980 eruption of Mount St. Helens. Such eruptions result when sufficient gas has dissolved under pressure within a viscous magma such ...
at Lassen Peak devastated nearby areas, and spread volcanic ash as far as to the east. This explosion was the most powerful in a series of eruptions from 1914 through 1917. Lassen Peak and Mount St. Helens in Washington were the only two volcanoes in the
contiguous United States The contiguous United States (officially the conterminous United States) consists of the 48 adjoining U.S. states and the Federal District of the United States of America. The term excludes the only two non-contiguous states, Alaska and Hawaii ...
to erupt during the 20th century. Lassen Volcanic National Park, which encompasses an area of , was created to preserve the areas affected by the eruption, for future observation and study, to protect the nearby volcanic features, and to keep anyone from settling too close to the volcano. The park, along with the nearby Lassen National Forest and Lassen Peak, have become popular destinations for recreational activities, including climbing, hiking, backpacking,
snowshoeing Snowshoes are specialized outdoor gear for walking over snow. Their large footprint spreads the user's weight out and allows them to travel largely on top of rather than through snow. Adjustable bindings attach them to appropriate winter footwe ...
,
kayaking Kayaking is the use of a kayak for moving over water. It is distinguished from canoeing by the sitting position of the paddler and the number of blades on the paddle. A kayak is a low-to-the-water, canoe-like boat in which the paddler sits fac ...
, and
backcountry skiing Backcountry skiing ( US), also called off-piste (Europe), alpine touring, or out-of-area, is skiing in the backcountry on unmarked or unpatrolled areas either inside or outside a ski resort's boundaries. This contrasts with alpine skiing, which i ...
. Lassen Peak is dormant, meaning the volcano is merely inactive, and it has a functioning magma chamber under the ground still capable of eruptions. Thus it poses a threat to the nearby area through
lava flow Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or und ...
s, pyroclastic flows,
lahar A lahar (, from jv, ꦮ꧀ꦭꦲꦂ) is a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a river valley. Lahars are extreme ...
s (volcanically induced
mudslide A mudflow or mud flow is a form of mass wasting involving fast-moving flow of debris that has become liquified by the addition of water. Such flows can move at speeds ranging from 3 meters/minute to 5 meters/second. Mudflows contain a significa ...
s,
landslide Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated grade (slope), slope failures, mudflows, and debris flows. Landslides occur in a variety of ...
s, and debris flows), ash, avalanches, and floods. To monitor this threat, Lassen Peak and the surrounding vicinity are closely observed with sensors by the California Volcano Observatory.


Geography

Located in Lassen Volcanic National Park, Lassen Peak lies in Shasta County, east of the city of Redding, in the U.S. state of California. Lassen Peak and the rest of the National Park area are surrounded by the Lassen National Forest, which has an area of . Nearby towns include Mineral in
Tehama County Tehama County ( ; Wintun for "high water") is a county located in the northern part of the U.S. state of California. As of the 2020 census, the population was 65,829. The county seat and largest city is Red Bluff. Tehama County comprises th ...
and Viola in Shasta County. Lassen Peak reaches an elevation of , according to 1992 data from the U.S. National Geodetic Survey; 1981 data from the Geographic Names Information System lists the mountain's elevation at . Lassen Peak marks the southernmost major volcano in the
Cascade Range The Cascade Range or Cascades is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, ...
, rising above the northern
Sacramento Valley , photo =Sacramento Riverfront.jpg , photo_caption= Sacramento , map_image=Map california central valley.jpg , map_caption= The Central Valley of California , location = California, United States , coordinates = , boundaries = Sierra Nevada (ea ...
. Bounded by the Sacramento Valley and the Klamath Mountains to the west and the Sierra Nevada mountain range to the south, it is the second tallest peak in the California segment of the Cascades, behind Mount Shasta, which lies to the north. Due to its proximity to nearby volcanoes
Mount Tehama 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 Moun ...
and Mount Diller, it is not easy to distinguish from its neighboring peaks.


Physical geography

Lassen Peak has the highest known winter
snowfall Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water throughout ...
amounts in California. There is an average annual snowfall of , and in some years, more than of snow falls at its base elevation of at Lake Helen. The Lassen Peak area receives more precipitation ( rain, sleet,
hail Hail is a form of solid precipitation. It is distinct from ice pellets (American English "sleet"), though the two are often confused. It consists of balls or irregular lumps of ice, each of which is called a hailstone. Ice pellets generally fal ...
, snow, etc.) than anywhere in the Cascade Range south of the Three Sisters volcanoes in Oregon. Though the volcano lies too far to the south to support a permanent snow cover over the entire mountain, the heavy annual snowfall on Lassen Peak creates fourteen permanent patches of snow on and around the mountain top, despite Lassen's rather modest elevation, but no glaciers. Lightning has been known to strike the area frequently during summer thunderstorms. These can initiate fires. On July 23, 2012, a lightning strike started the Reading Fire to the northeast of the Paradise Meadow region, which was contained after it reached an area of . During the summer and fall of 2016, the National Park Service carried out prescribed fires to help reduce the amount of fuel available for fires in the Mineral Headquarters area and the Manzanita and Juniper Lake areas, respectively.


Ecology

Lassen Peak supports a variety of flora that include mountain hemlock, whitebark pine, and alpine wildflowers. Mountain hemlocks generally only reach an elevation of , while whitebark pines reach up to . Throughout the national park, forests can be found featuring red fir, mountain alder, western white pine, white fir, lodgepole pine,
Jeffrey pine ''Pinus jeffreyi'', also known as Jeffrey pine, Jeffrey's pine, yellow pine and black pine, is a North American pine tree. It is mainly found in California, but also in the westernmost part of Nevada, southwestern Oregon, and northern Baja Califo ...
, ponderosa pine, incense cedar,
juniper Junipers are coniferous trees and shrubs in the genus ''Juniperus'' () of the cypress family Cupressaceae. Depending on the taxonomy, between 50 and 67 species of junipers are widely distributed throughout the Northern Hemisphere, from the Arcti ...
, and live oak. Other plants found in the Lassen Peak area consist of coyote mint, lupines, mule's ears, ferns, corn lilies, red mountain heathers, pinemat manzanitas, greenleaf manzanitas, bush chinquapins, catchflies, Fremont's butterweed, buckwheat, granite
gilia ''Gilia'' is a genus of between 25 and 50 species of flowering plants in the Polemoniaceae family and is related to phlox. These Western native plants are best sown in sunny, well-draining soil in the temperate and tropical regions of the Ameri ...
, mountain pride, mariposa tulips,
creambush ''Holodiscus discolor'', commonly known as ocean spray or oceanspray, creambush, or ironwood, is a shrub of western North America. Description ''Holodiscus discolor'' is a fast-growing deciduous shrub usually from to in height, and up to ta ...
, and a variety of
chaparral Chaparral ( ) is a shrubland plant community and geographical feature found primarily in the U.S. state of California, in southern Oregon, and in the northern portion of the Baja California Peninsula in Mexico. It is shaped by a Mediterranean c ...
shrubs. The various habitats in the Lassen Volcanic National Park support about 300 vertebrate species like mammals,
reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...
s,
amphibian Amphibians are tetrapod, four-limbed and ectothermic vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terres ...
s, fish, and birds, including
bald eagle The bald eagle (''Haliaeetus leucocephalus'') is a bird of prey found in North America. A sea eagle, it has two known subspecies and forms a species pair with the white-tailed eagle (''Haliaeetus albicilla''), which occupies the same niche as ...
s, which are listed as "Threatened" under the Endangered Species Act of 1973, and
peregrine falcon The peregrine falcon (''Falco peregrinus''), also known as the peregrine, and historically as the duck hawk in North America, is a Cosmopolitan distribution, cosmopolitan bird of prey (Bird of prey, raptor) in the family (biology), family Falco ...
s, which were removed from the endangered species list in 1999. In forested areas below , animals include
American black bear The American black bear (''Ursus americanus''), also called simply a black bear or sometimes a baribal, is a medium-sized bear endemic to North America. It is the continent's smallest and most widely distributed bear species. American black bear ...
s, mule deer,
marten A marten is a weasel-like mammal in the genus ''Martes'' within the subfamily Guloninae, in the family Mustelidae. They have bushy tails and large paws with partially retractile claws. The fur varies from yellowish to dark brown, depending on t ...
s, brown creepers, mountain chickadees,
white-headed woodpecker The white-headed woodpecker (''Leuconotopicus albolarvatus'') is a non-migratory woodpecker that resides in pine forests of the mountains of western North America. Description It has a black body (approximately long) and white head. It has whit ...
s,
long-toed salamander The long-toed salamander (''Ambystoma macrodactylum'') is a mole salamander in the family Ambystomatidae. This species, typically long when mature, is characterized by its mottled black, brown, and yellow pigmentation, and its long outer fourth ...
s, and several bat species. At higher elevations, Clark's nutcrackers,
deer mice Deer or true deer are hoofed ruminant mammals forming the family Cervidae. The two main groups of deer are the Cervinae, including the muntjac, the elk (wapiti), the red deer, and the fallow deer; and the Capreolinae, including the reindeer ...
, and chipmunks can be found among mountain hemlock stands, and subalpine zones with sparse vegetation host populations of
gray-crowned rosy finch The gray-crowned rosy finch or gray-crowned rosy-finch (''Leucosticte tephrocotis'') is a species of passerine bird in the family Fringillidae native to Alaska, western Canada, and the north-western United States. Due to its remote and rocky alp ...
es, pikas, and
golden-mantled ground squirrel The golden-mantled ground squirrel (''Callospermophilus lateralis'') is a ground squirrel native to western North America. It is distributed in the Rocky Mountains of British Columbia and Alberta, and through much of the western United States. ...
s. Among scattered stands of pinemat manzanita, red fir, and lodgepole pine, animals include dark-eyed juncos, montane voles, and
sagebrush lizard The sagebrush lizard or sagebrush swift (''Sceloporus graciosus'') is a common species of phrynosomatid lizard found at mid to high altitudes in the western United States of America. It belongs to the genus ''Sceloporus'' (spiny lizards) in ...
s. Meadows at the bottoms of valleys along streams and lakes support
Pacific tree frog The Pacific tree frog (''Pseudacris regilla''), also known as the Pacific chorus frog, has a range spanning the Pacific Northwest, from Northern California, Oregon, and Washington to British Columbia in Canada and extreme southern Alaska. They l ...
s,
Western terrestrial garter snake The western terrestrial garter snake (''Thamnophis elegans'') is a western North American species of colubrid snake. At least five subspecies are currently recognized. Description Most western terrestrial garter snakes have a yellow, light orang ...
s, common snipes, and
mountain pocket gopher The mountain pocket gopher (''Thomomys monticola'') is a species of rodent in the family Geomyidae. It is endemic to California and Nevada Nevada ( ; ) is a state in the Western region of the United States. It is bordered by Oregon to the ...
s. Other animals found within the national park area include snakes like
rubber boa The rubber boa (''Charina bottae'') is a species of snake in the family Boidae and is native to North America. It is sometimes known as the coastal rubber boa or the northern rubber boa and is not to be confused with the southern rubber boa (''C ...
s, common garter snakes, and
striped whipsnake The striped whipsnake (''Masticophis taeniatus'') is a species of nonvenomous snake in the family Colubridae. It is closely related to the California whipsnake ('' Masticophis lateralis''). The striped whipsnake is native to the western United St ...
s;
cougar The cougar (''Puma concolor'') is a large Felidae, cat native to the Americas. Its Species distribution, range spans from the Canadian Yukon to the southern Andes in South America and is the most widespread of any large wild terrestrial mamm ...
s; amphibians like newts, salamanders, rough-skinned newts, and
Cascades frog The Cascades frog (''Rana cascadae'') is a species of frog in the family Ranidae found in the Pacific Northwest, mainly in the Cascade Range and Olympic Mountains. Description Appearance The Cascades frog has a green to brown color on its b ...
s; 216 species of birds including MacGillivray's warblers,
Wilson's warbler Wilson's warbler (''Cardellina pusilla'') is a small New World warbler. It is greenish above and yellow below, with rounded wings and a long, slim tail. The male has a black crown patch; depending on the subspecies, that mark is reduced or absent ...
s, song sparrows, spotted owls,
northern goshawk The northern goshawk (; ''Accipiter gentilis'') is a species of medium-large bird of prey, raptor in the Family (biology), family Accipitridae, a family which also includes other extant diurnal raptors, such as eagles, buzzards and harrier (bird) ...
s, and
bufflehead The bufflehead (''Bucephala albeola'') is a small sea duck of the genus ''Bucephala'', the goldeneyes. This species was first described by Carl Linnaeus in his landmark 1758 10th edition of ''Systema Naturae'' as ''Anas albeola''. The genus na ...
ducks; five species of native fish that include
rainbow trout The rainbow trout (''Oncorhynchus mykiss'') is a species of trout native to cold-water tributaries of the Pacific Ocean in Asia and North America. The steelhead (sometimes called "steelhead trout") is an anadromous (sea-run) form of the coasta ...
, tui chubs, speckled daces,
Lahontan redside The Lahontan redside (''Richardsonius egregius'') is a cyprinid fish of the Great Basin in eastern California and western Nevada. Lahontan redsides are noted for their breeding colors, consisting of a bright red stripe with a yellow border on ea ...
s, and
Tahoe sucker The Tahoe sucker (''Catostomus tahoensis'') is a freshwater Cypriniform fish inhabiting the Great Basin region of the Western United States. Description The Tahoe sucker is a large, long fish with a tapering head. It can grow up to 24 inches in ...
s; and four
invasive Invasive may refer to: *Invasive (medical) procedure *Invasive species *Invasive observation, especially in reference to surveillance *Invasively progressive spread of disease from one organ in the body to another, especially in reference to cancer ...
fish species including
brook trout The brook trout (''Salvelinus fontinalis'') is a species of freshwater fish in the char genus ''Salvelinus'' of the salmon family Salmonidae. It is native to Eastern North America in the United States and Canada, but has been introduced elsewhere ...
,
brown trout The brown trout (''Salmo trutta'') is a European species of salmonid fish that has been widely introduced into suitable environments globally. It includes purely freshwater populations, referred to as the riverine ecotype, ''Salmo trutta'' morph ...
, golden shiners, and fathead minnows. Prominent invertebrate species include
California tortoiseshell The California tortoiseshell (''Nymphalis californica'') is a butterfly of the family Nymphalidae. The wings of the California tortoiseshell have ragged edges. The upper sides of the wings are orange with black spots and a wide black margin. The ...
butterflies.


Geology

Lassen Peak lies near the southern end of the Cascade Volcanic Arc, at the western edge of the Basin and Range Province. Like other Cascade volcanoes, it was fed by magma chambers produced by the
subduction Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...
of the oceanic Juan de Fuca tectonic plate under the western edge of the continental North American tectonic plate. The region is also affected geologically by the Cascadia subduction zone, which dips eastward beneath the western coast of North America in the Pacific Northwest, as well as horizontal stretching to the east of crustal rock in the Basin and Range Province. About 3 million years ago, the southern limit of active volcanoes in the Cascades corresponded to the Yana Volcanic Center to the south of Lassen Peak, but currently the southern edge of the Lassen Volcanic National Park now marks the same border, indicating that the Cascade Arc's southern end migrates at a rate of annually. In the southern segment of the Cascades, volcanoes exhibit widespread and long-lived activity produced by magma that ranges from low- silica basalt to siliceous (silica-rich)
rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral ...
. The Lassen volcanic center is fed by two magma chambers, one calc-alkaline reservoir common to the rest of the Cascade Volcanoes, and the other a smaller volume of low-potassium olivine tholeiitic basalt associated with the Basin and Range province. Within the region, most if not all of the volcanic rock has erupted in the past 3 million years. During this period, at least five large andesitic stratovolcanoes (such as Mount Maidu) formed in the vicinity of Lassen Volcanic National Park, building volcanic cones before going extinct and undergoing erosion. For most volcanic centers in the Southern Cascades, one volcano becomes active and normally becomes extinct as another begins to erupt, but at the Lassen locus, the Maidu and Dittmar volcanic centers overlapped during the late Pliocene to the early Pleistocene. Volcanism within the Lassen vicinity follows a trend of intermittent, episodic eruptions punctuating long periods of dormancy, a pattern which persisted through the late Pleistocene and Holocene. During the past 825,000 years, the area has produced hundreds of
explosive eruption In volcanology, an explosive eruption is a volcanic eruption of the most violent type. A notable example is the 1980 eruption of Mount St. Helens. Such eruptions result when sufficient gas has dissolved under pressure within a viscous magma such ...
s over an area of , and the past 50,000 years have seen seven major silicic eruptive episodes that produced dacitic
lava dome In volcanology, a lava dome is a circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions on ...
s, tephra, and pyroclastic flows, along with five periods of basaltic and andesitic
lava flow Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or und ...
s. Local activity began 600,000 years ago with the formation of Brokeoff Volcano (alternatively known as Mount Tehama). Around the same time, about 614,000 years ago, an explosive eruption southwest of Lassen Peak produced of pumice and ash, covering the area between the vent and what is now the city of Ventura, California. This deposit, referred to as the Rockland tephra, reaches up to several inches in thickness within the San Francisco Bay area, and can be found as far as northern Nevada and southern Idaho. The same eruption also formed one of three known calderas within the Cascade, the others being Crater Lake and the Kulshan Caldera at Mount Baker. Shortly after, the Lassen volcanic center, a cluster of closely spaced volcanoes, formed in the area, covering the nearby caldera. During the late Pleistocene it produced andesite lava flows that built the Brokeoff composite volcano (stratovolcano). Following the end of volcanism at Brokeoff Volcano hydrothermal fluids began chemically weathering minerals in the andesite flows, altering the once strong rocks into easily eroded materials. Glaciers and streams were able to rapidly erode deep channels into these altered volcanic rocks, reducing the once lofty peak of Brokeoff Volcano into the landscape we see today. Following the erosion of Brokeoff Volcano, volcanism migrated to the Lassen Domefield to the northeast. Lassen Peak's lava dome formed about 27,000 years ago from a series of eruptions over a few years, undergoing significant glacial erosion between 25,000 and 18,000 years ago. The bowl-shaped depression on the volcano's northeastern flank, called a
cirque A (; from the Latin word ') is an amphitheatre-like valley formed by glacial erosion. Alternative names for this landform are corrie (from Scottish Gaelic , meaning a pot or cauldron) and (; ). A cirque may also be a similarly shaped landform ...
, was eroded by a glacier that extended out from the dome. By 18,000 years ago, Lassen Peak started to form a mound-shaped dacite lava dome, pushing its way through Tehama's former northern flank. As the lava dome grew it shattered overlaying rock, which formed a blanket of angular talus around the emerging steep-sided volcano. Likely resembling the nearby 1,100-year-old
Chaos Crags Chaos Crags is the youngest group of lava domes in Lassen Volcanic National Park, California. They formed as six dacite domes 1,100-1,000 years ago, one dome collapsing during an explosive eruption about 70 years later. The eruptions at the Ch ...
, Lassen Peak reached its present height in a relatively short time, probably in just a few years. Within the past 1,000 years or so, activity at Lassen Peak has produced six dacite lava domes, erupted tephra and pyroclastic flows, and built
Cinder Cone and the Fantastic Lava Beds Cinder Cone is a cinder cone volcano in Lassen Volcanic National Park within the United States. It is located about northeast of Lassen Peak and provides an excellent view of Brokeoff Mountain, Lassen Peak, and Chaos Crags. The cone was bui ...
. It also created the rockfalls at Chaos Jumbles. The only Cascade volcano with an elevation above that is not a stratovolcano, Lassen Peak is a
rhyodacitic Rhyodacite is a volcanic rock intermediate in composition between dacite and rhyolite. It is the extrusive equivalent of those plutonic rocks that are intermediate in composition between monzogranite and granodiorite. Rhyodacites form from rapid ...
lava dome. It represents one of the largest lava domes on Earth, with a height of above its surroundings, and an approximate volume of . Unlike more conventional, conical stratovolcanoes like Mount Shasta or Mount Rainier, Lassen Peak is part of a volcanic center that erupts from different vents, which each remain active for a number of years or decades but often do not erupt from the same vent twice, also known as a monogenetic volcanic field. 2000 years after Lassen's formation, it was surrounded by glaciers which ate away at its spiny protrusions of dacite. Due to glacial erosion from the last local glacial advance, which ceased roughly 15,000 years ago, Lassen's lava dome is now covered in broken rock fragments at the base of crags called talus deposits. Only its crag formations on its southern flank, near the summit trailhead, have not been significantly altered by glacial erosion.


Subfeatures

The Lassen volcanic center includes Brokeoff Volcano, Lassen's dacitic lava dome, and a number of small andesitic
shield volcano A shield volcano is a type of volcano named for its low profile, resembling a warrior's shield lying on the ground. It is formed by the eruption of highly fluid (low viscosity) lava, which travels farther and forms thinner flows than the more v ...
es found northeast of Lassen Peak. The Lassen dome field includes 30 dacitic lava domes such as Bumpass Mountain, Mount Helen, Ski Heil Peak, and Reading Peak; other major lava domes include Chaos Crags, Eagle Peak, Sunflower Flat, and Vulcans Castle. Nearby shield volcanoes include Prospect Peak and West Prospect Peak, and there are three cones close to Lassen Peak: Cinder Cone, Hat Mountain, and Raker Peak. The hydrothermal area inside the Lassen Peak volcanic center, with features located southeast and southwest of Lassen Peak, represents the largest geothermal area in the United States besides the one present at Yellowstone National Park. The Chaos Crags, a series of five small lava domes, represent the youngest part of Lassen volcanic center's dome field, reaching an elevation of about above their surroundings. They were produced by vigorous explosive eruptions of pumice and ash followed by
effusive In physics and chemistry, effusion is the process in which a gas escapes from a container through a hole of diameter considerably smaller than the mean free path of the molecules. Such a hole is often described as a ''pinhole'' and the escape ...
activity, which created unstable edifices that partially collapsed and formed pyroclastic flows made of incandescent lava blocks and lithic ash. Six domes were originally formed, though one was destroyed by a pyroclastic flow. Roughly 350 years ago, one of the domes collapsed to produce the Chaos Jumbles, an area where three enormous rockfalls transformed the local area and traveled as far as down the dome's slopes. Cinder Cone, which reaches an elevation of above its surrounding area in the northeastern region of the Lassen Volcanic National Park, forms a symmetrical pyroclastic cone. The youngest mafic volcano in the Lassen volcanic center, it is surrounded by unvegetated block lava and has concentric craters at its summit. Cinder Cone is comprised by five
basaltic andesite Basaltic andesite is a volcanic rock that is intermediate in composition between basalt and andesite. It is composed predominantly of augite and plagioclase. Basaltic andesite can be found in volcanoes around the world, including in Central Ameri ...
and andesite lava flows, and it also has two
cinder cone A cinder cone (or scoria cone) is a steep conical hill of loose pyroclastic fragments, such as volcanic clinkers, volcanic ash, or scoria that has been built around a volcanic vent. The pyroclastic fragments are formed by explosive eruptions o ...
volcanoes, with two scoria cones, the first of which was mostly destroyed by lava flows from its base. In 1850 and 1851, a number of observers reported an eruption at Cinder Cone visible from more than away, with one observer near the mountain claiming to have observed a lava flow "running down the sides of the volcano." However, despite these testimonies and accounts in newspaper articles and several scientific journals, the veracity of these eruptions has been questioned by scientists from the United States Geological Survey. In addition to the fact that cinder cones usually erupt lava from base vents, there is a lack of physical evidence suggesting activity at the volcano since its formation in 1650. In addition, an old willow bush growing near the summit crater that was documented during the 1850s was still present in the 1880s after the alleged eruptions, suggesting that no eruptions took place during the 1850s.


Human history

The areas surrounding Lassen Peak, especially to its east, south, and southeast, represented a meeting ground for Maidu,
Yana Yana may refer to: Locations *Yana, Burma, a village in Hkamti Township in Hkamti District in the Sagaing Region of northwestern Burma *Yana, India, a village in the Uttara Kannada district of Karnataka, India * Yana, Nigeria, an administrative ca ...
, Yahi, and Atsugewi Native Americans. The volcano is known among some native populations as ''Amblu Kai'', which means "Mountain Ripped Apart" or "Fire Mountain," and as ''Kom Yamani,'' which means "Snow Mountain," among the Mountain Maidu. Because the area was not suitable for permanent habitation, there is relatively scarce archaeological evidence of a native presence in the Lassen area. The first white man to reach Lassen Peak was
Jedediah Smith Jedediah Strong Smith (January 6, 1799 – May 27, 1831) was an American clerk, transcontinental pioneer, frontiersman, hunter, trapper, author, cartographer, mountain man and explorer of the Rocky Mountains, the Western United States, and ...
, who passed through the area in 1821 as he made his way for the western coast of the United States. After the
California Gold Rush The California Gold Rush (1848–1855) was a gold rush that began on January 24, 1848, when gold was found by James W. Marshall at Sutter's Mill in Coloma, California. The news of gold brought approximately 300,000 people to California fro ...
brought increased numbers of settlers into the area, Lassen Peak was named in honor of a Danish blacksmith, Peter Lassen, who guided immigrants past the peak to the
Sacramento Valley , photo =Sacramento Riverfront.jpg , photo_caption= Sacramento , map_image=Map california central valley.jpg , map_caption= The Central Valley of California , location = California, United States , coordinates = , boundaries = Sierra Nevada (ea ...
during the 1830s. This trail was replaced by the
Nobles Emigrant Trail The Nobles Emigrant Trail, also known as the Fort Kearney, South Pass and Honey Lake Wagon Road, is a trail in California that was used by emigrant parties from the east as a shortened route to northern California. It was pioneered in 1851 by Willi ...
, named for the guide William Nobles, who pioneered the trail in 1851. Lassen Peak's first recorded ascent took place in 1851, led by Grover K. Godfrey. In 1864, painter
Helen Tanner Brodt Helen Alice Tanner Brodt (April 21, – ) was an American landscape and portrait painter. Helen Tanner was born on April 21, in Elmira, New York. She studied art at the National Academy of Design. She married Aurelius W. Brodt, a school ...
became the first woman to reach the summit of Lassen Peak, wanting to sketch the surrounding landscape. A tarn lake on Lassen Peak is named "Lake Helen" in her honor. The Bumpass Hell, a hydrothermal vent area near Lassen Peak, was named after a pioneer who suffered burns there and lost his leg shortly after. Other historic names for Lassen Peak include Mount Joseph (from 1827), Snow Butte, Sister Buttes, and Mount Lassen.


Lassen Volcanic National Park

United States President Theodore Roosevelt established the Lassen Peak National Monument in 1907. Despite Native population claims that Lassen Peak was "full of fire and water" and would erupt again, this motion was based on the general belief that Lassen Peak was now
extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
, and that its vicinity contained intriguing volcanic phenomena, which could be studied and observed. Once the volcano became active again in 1914, the monument was expanded to establish the Lassen Volcanic National Park on August 9, 1916. The park, in area, can be reached from the California State Route 89 highway.


Eruptive history


Ancient activity

Between 385,000 and 315,000 years ago, volcanism at the Lassen center shifted from andesitic stratovolcano construction to production of dacite domes. Over the past 300,000 years, the Lassen Peak area has produced more than 30 lava domes, Lassen Peak being the largest. These lava domes formed as a result of rising lava that was pushed up but was too viscous to escape its source, creating steep edifices. Lassen Peak's lava dome formed 27,000 years ago from a series of eruptions over a few years, undergoing significant glacial erosion between 25,000 and 18,000 years ago. No volcanic activity took place 190,000 years ago to roughly 90,000 years ago, but during the last 100,000 years, there have been at least 12 periods of eruptive activity in the Lassen volcanic center, and since 90,000 years ago, the Twin Lakes sequence has been producing mixed lavas with variable appearances and compositions, including andesite and basaltic andesite lava flows and agglutinated volcanic cones (made of fused pyroclastic rocks) located by the Lassen dome field. The Twin Lakes sequence includes the construction of the Chaos Crag dome complex between 1100 and 1000 years ago and eruptions at Lassen Peak beginning in 1914. Prior to 1914, Lassen Peak likely underwent at least one explosive eruption, which created a summit crater deep with a diameter of . Deposits from older mudflows that can be traced specifically to the Lassen dome have also been found in Hat Creek, Lost Creek, and in a region to the east of the Devastated Area.


1914–1921

On May 30, 1914, despite an apparent lack of precursor earthquakes, Lassen became volcanically active again after 27,000 years of
dormancy Dormancy is a period in an organism's life cycle when growth, development, and (in animals) physical activity are temporarily stopped. This minimizes metabolic activity and therefore helps an organism to conserve energy. Dormancy tends to be clo ...
, when it produced a steam explosion that carved out a small crater with a fairly deep lake on the volcano's summit. The crater grew as it was carved by more than 180 similar phreatic explosions over the span of more than 11 months, reaching a length of . On May 14, 1915, Lassen Peak erupted lava blocks, which extended as far as Manton, west of the mountain. By the next day, the volcano had produced a dacitic lava dome, between 63 and 68 percent silica, which occupied its summit crater. On May 19, a large eruption destroyed this dome, and a new crater formed at the summit. No lava erupted, but parts of the dome fell on the upper flanks of the mountain, which were covered in more than of snow. The lava mixed with snow and rock to form a
lahar A lahar (, from jv, ꦮ꧀ꦭꦲꦂ) is a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a river valley. Lahars are extreme ...
(volcanically induced
mudslide A mudflow or mud flow is a form of mass wasting involving fast-moving flow of debris that has become liquified by the addition of water. Such flows can move at speeds ranging from 3 meters/minute to 5 meters/second. Mudflows contain a significa ...
,
landslide Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated grade (slope), slope failures, mudflows, and debris flows. Landslides occur in a variety of ...
, and debris flow), in width, which coursed down the side of the volcano, traveling and reaching Hat Creek. After being deflected to the northwest at Emigrant Pass, the lahar extended an additional down Lost Creek. On May 20, the lower Hat Creek valley flooded with muddy water, which damaged ranch houses in the Old Station area and caused minor injuries among a few people, all of whom escaped. Removing homes from their foundation, the lahar also uprooted trees more than tall. The flood continued for another , killing fish in the
Pit River The Pit River is a major river draining from northeastern California into the state's Central Valley. The Pit, the Klamath and the Columbia are the only three rivers in the U.S. that cross the Cascade Range. The longest tributary of the Sacr ...
. Simultaneously, dacite lava with lower viscosity than dacite from the previous eruption filled the summit crater, overflowing and extending in two streams for down the mountain's western and northeastern sides. On May 22, 1915, at about 4:00 p.m., Lassen Peak produced a violent explosive eruption that ejected rock and pumice and formed a larger and deeper crater at its summit. Within 30 minutes, volcanic ash and gas formed a column that reached altitudes of more than and could be seen from the city of Eureka, to the west. This column underwent a partial collapse, generating a pyroclastic flow composed of hot ash, pumice, rock, and gas that destroyed of land and spawned a lahar extending from the volcano and again reaching Hat Creek Valley. Smaller mudflows also formed on every side of the volcano, as well a layer of pumice and volcanic ash that reached as far as northeast; volcanic ash was detected up to east at the city of
Elko, Nevada Elko (Shoshoni: Natakkoa, "Rocks Piled on One Another") is the largest city in and county seat of Elko County, Nevada, United States. With a 2020 population of 20,564, Elko is currently growing at a rate of 0.31% annually and its population has i ...
. Additionally, the lava flow on the volcano's northeastern flank was removed by this eruption, but not the similar deposit on the western flank. The eruptive output volume totaled , dwarfed by the
1980 eruption of Mount St. Helens On March 27, 1980, a series of volcanic explosions and pyroclastic flows began at Mount St. Helens in Skamania County, Washington, United States. A series of phreatic blasts occurred from the summit and escalated until a major explosive eru ...
, which had a volume of . The region on the volcano's northeastern flank destroyed by the eruptions, in area, is now known as the Devastated Area, and it along with other deposits from the volcano has been altered by erosion and regrowth of vegetation, though the vegetation in Devastated Area is sparse due to its siliceous (rich in silica), nutrient-deprived soil, which cannot sustain normal tree growth due to its lack of water retention. Due to their small size and thin deposits, the 1915 eruptions will likely not be well-preserved geologically. After 1915, steam explosions continued for several years, indicating extremely hot rock beneath Lassen Peak's surface. In May 1917, an especially strong steam explosion formed the northern crater on Lassen Peak's summit, with eruptions lasting two days and producing an ash cloud that extended into the sky. June saw 21 additional explosions reported, further transforming the crater and creating a new vent on Lassen Peak's northwestern summit. In June 1919, steam eruptions occurred, and similar activity was observed on April 8 and 9 in 1920, followed by steam eruptions lasting 10–12 hours in October of the same year. During February 1921, white steam erupted from eastern fissures on the volcano. In total, about 400 eruptions were observed between 1914 and 1921, which were the last eruptions in the Cascades before the 1980 eruption of Mount St. Helens, which was the only other volcanic eruption in the
contiguous United States The contiguous United States (officially the conterminous United States) consists of the 48 adjoining U.S. states and the Federal District of the United States of America. The term excludes the only two non-contiguous states, Alaska and Hawaii ...
during the 20th century.


Documentation of 20th century eruptions through pictures and film

During its eruptions in the early 20th century, Lassen Peak attracted widespread media attention as the first volcano to erupt in the United States during the 20th century. Unlike eruptions at Mount Baker,
Mount Rainier Mount Rainier (), indigenously known as Tahoma, Tacoma, Tacobet, or təqʷubəʔ, is a large active stratovolcano in the Cascade Range of the Pacific Northwest, located in Mount Rainier National Park about south-southeast of Seattle. With a s ...
, Mount St. Helens, or
Mount Hood Mount Hood is a potentially active stratovolcano in the Cascade Volcanic Arc. It was formed by a subduction zone on the Pacific coast and rests in the Pacific Northwest region of the United States. It is located about east-southeast of Portlan ...
during the 19th century, Lassen Peak's eruptions were very well documented by newspapers and extensively photographed. Though there is a large supply of images documenting these eruptions at Lassen Peak, the best and most complete images were taken by the local businessman Benjamin Franklin Loomis. Using an 8x10-inch camera with glass-plate negatives, Loomis made his own film and set up a darkroom in a tent. He wrote of the eruption he witnessed on June 14, 1914, "The sight was fearfully grand." Loomis's pictures were published in his book ''Pictorial History of the Lassen Volcano'' (1926); a number of his original plates remain in the archives of the National Park Service. His photographs have been used to help understand the timeline and geology of the 1915 eruptions of Lassen Peak. One of Lassen Peak's 1917 eruptions was captured on film by Justin Hammer from the nearby Catfish Lake. Originally silent, the film features sound effects added by his grandson, Craig Martin. The film was rediscovered and published in 2015 by the Shasta Historical Society.


Recent activity and current threats

Lassen Peak remains an
active volcano An active volcano is a volcano which is either erupting or is likely to erupt in the future. An active volcano which is not currently erupting is known as a dormant volcano. Overview Tlocene Epoch. Most volcanoes are situated on the Pacific Ri ...
, as volcanic activity including fumaroles (steam vents), hot springs, and mudpots can be found throughout Lassen Volcanic National Park. Their activity varies based on the season; during the spring, when meltwater is more abundant, fumaroles and pools of water have lower temperatures, while mudpots have more fluid mud supplies. During summer and droughts, they become drier and hotter, since they cannot be cooled by ground water. Geothermal activity can be observed at Bumpass Hell, Little Hot Springs Valley, Pilot Pinnacle, Sulphur Works, Devils Kitchen, Boiling Springs Lake, and Terminal Geyser, as well as the Morgan and Growler Hot Springs south of the national park in Mill Canyon. These are produced by the boiling of underground bodies of water, which generates steam. At Bumpass Hell, these features are at their most vigorous, with temperatures reaching at Big Boiler, the park's biggest fumarole and one of the hottest hydrothermal fumaroles in the world. Because of their acidic conditions and heat, none of these hydrothermal bodies are safe for bathing except for at Drakesbad Guest Ranch. Fumaroles near Lassen Peak in particular remained active through the 1950s, but have grown weaker over time; they can still be found among the volcano's summit craters. These hydrothermal features are monitored continuously for their physical and chemical conditions by the United States Geological Survey. Climbers reported steam eruptions in the summit craters for decades after activity apparently ceased in 1921, and the naturalist Paul Schulz documented 30 steam vents at the summit in the 1950s. A report from the United States Geological Survey declared that "No one can say when, but it is almost certain that the Lassen area will experience volcanic eruptions again." Similarly, the California Volcano Observatory lists its threat level as "Very High." At the time of the early 20th century eruptions, the area surrounding the volcano was only sparsely populated, but a similar eruption today would threaten many lives and the northern Californian economy. Volcanic eruptions occur with similar frequency to major earthquakes from the San Andreas Fault, and at least 10 eruptions have taken place within the state during the past 1,000 years, the most recent at Lassen Peak. Under 1 percent of the state's population lives within hazard zones that could be affected by an eruption, but collectively hazard zones are visited by more than 20 million people each year. Moreover, a number of the potentially active Californian volcanoes reside less than from highly populated areas, and explosive eruptions could produce ash that travels for several hundred miles. In the case of signs that suggest impending volcanic activity, the United States Geological Survey has a plan in place to utilize portable monitoring instruments, deploy scientists to the area, and implement an emergency response plan developed by the National Park Service if an eruption were imminent. Although basaltic lava flows are the most common eruptive activity in the Lassen volcanic center, they could also produce more violent and thus more hazardous silicic lava flows, in addition to building additional, unstable lava domes that could collapse and spawn pyroclastic flows that could extend for several miles. Because Lassen Peak has a significant amount of snow and ice, these pyroclastic flows (or hot volcanic ash) might mix with water to form lahars (volcanically induced mudslides, landslides, and debris flows) that could destroy nearby communities. Dacitic eruptions could produce volcanic columns of gas and ash that could threaten aircraft in the area. Moreover, the Lassen volcanic center poses threats to visitors from sudden avalanches that could be entirely unrelated to eruptive activity. Due to the threat of an avalanche from nearby Chaos Crag if volcanic activity renewed in the area or an earthquake occurred, the Visitor Center for Lassen Peak located at Manzanita Lake closed in 1974. In 1993, a rockfall with a volume of fell down Lassen Peak's northeastern flank, but no visitors were harmed. Despite the volcano's current quiet state, rockfalls still pose significant hazards due to the peak's inherent instability. The volcano is monitored by the California Volcano Observatory, which has a sensor network that can measure increased seismicity, ground deformation, or gas emissions suggesting movement of magma towards the surface near the volcano. The United States Geological Survey, in cooperation with the National Park Service, has been monitoring Lassen Peak and other volcanic areas in the park with tiltmeters, seismometers, and
inclinometer An inclinometer or clinometer is an measuring instrument, instrument used for measuring angles of slope, elevation, or depression (geology), depression of an object with respect to gravity's direction. It is also known as a ''tilt indicator'', ' ...
s. Prior to 1996, geodetic surveys at Lassen Peak did not detect ground deformation, but
Interferometric synthetic-aperture radar Interferometric synthetic aperture radar, abbreviated InSAR (or deprecated IfSAR), is a radar technique used in geodesy and remote sensing. This geodetic method uses two or more synthetic aperture radar (SAR) images to generate maps of surface defor ...
(InSAR) surveys between 1996 and 2000 suggested that downward
subsidence Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope move ...
was occurring at a rate of each year within a circular area with a diameter of centered just of the volcano. As a result, additional surveys using the
Global Positioning System The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite sy ...
took place in 2004, and further InSAR surveys showed that subsidence continued through 2010. Lassen Peak is one of four Cascade volcanoes that has undergone subsidence since 1990, with Medicine Lake Volcano, Mount Baker, and Mount St. Helens. Though not conclusively linked to a possible eruption, this subsidence may offer insight into how magma is stored within the region, tectonic setting, and how hydrothermal systems evolve over long periods of time. GPS receivers have been in place to monitor deformation within the Lassen volcanic center since 2008, and 13 seismometers in the vicinity, first installed in 1976 and since updated each decade, continually survey earthquakes within the locale.


Recreation

The Lassen Volcanic National Park is visited by more than 350,000 people every year. Incorporating more than of hiking trails, it is visited by people looking to hike or backpack during the summers. Popular winter activities include
snowshoeing Snowshoes are specialized outdoor gear for walking over snow. Their large footprint spreads the user's weight out and allows them to travel largely on top of rather than through snow. Adjustable bindings attach them to appropriate winter footwe ...
and
backcountry skiing Backcountry skiing ( US), also called off-piste (Europe), alpine touring, or out-of-area, is skiing in the backcountry on unmarked or unpatrolled areas either inside or outside a ski resort's boundaries. This contrasts with alpine skiing, which i ...
. As the second-tallest volcano in Northern California, trailing only Mount Shasta, Lassen Peak is frequently visited by climbers and hikers from around the world. The summit opens for use most years near the end of June, remaining in use until heavy snow falls in October or November. After a 9-year-old boy died from a collapsed retaining wall along the summit trail on July 29, 2009, the path closed for six years for construction, reopening in 2015. The mountain's summit trail can be accessed from a parking lot on the northern side of the California State Route 89. The Lassen Peak Trail, which starts from this parking area, runs for with switchback turns, a round-trip hike in length that ascends approximately from the trailhead at to the summit at . From the northeast summit, Lassen's 1915 mudflow and Prospect Peak are visible; the northwestern summit offers views of Lassen's two bowl-shaped craters and Mount Shasta, to the north. The southern entrance to the park area has a winter sports area where visitors can ski, snowshoe, and within the Lassen National Forest, visitors can also bicycle, go
boating Boating is the leisurely activity of travelling by boat, or the recreational use of a boat whether Motorboat, powerboats, Sailing, sailboats, or man-powered vessels (such as rowing and paddle boats), focused on the travel itself, as well as sp ...
, or use snowmobiles.


See also

* List of highest points in California by county * List of Ultras of the United States * List of volcanoes in the United States


References


Sources

* * * * * * * * * * * * * *


External links

* * * {{Authority control Cascade Range Volcanoes of Shasta County, California Highest points of United States national parks Lassen Volcanic National Park Subduction volcanoes Pleistocene lava domes Cascade Volcanoes Cirques 20th-century volcanic events Volcanoes of California North American 3000 m summits Holocene lava domes