Lassen Peak
Lassen Peak and Devastated Area from Cinder Cone
Elevation	10,457 feet (3,187 m)
Location	California, USA
Range	Cascade Range
Prominence	5,229 feet (1,594 m)
Coordinates	40°29′17.42″N 121°30′18.03″W / 40.4881722, -121.5050083
Topo map	USGS Lassen Peak
Type	Lava dome
Volcanic arc/belt	Cascade Volcanic Arc
Age of rock	< 27,000 years
Last eruption	1917
Easiest route	hike

Lassen Peak^[1] (also known as Mount Lassen) is the southernmost active volcano in the Cascade Range. It is part of the Cascade Volcanic Arc which is an arc that stretches from northern California to southwestern British Columbia. Located in the Shasta Cascade region of Northern California, Lassen rises 2,000 feet (610 m) above the surrounding terrain and has a volume of half a cubic mile, making it one of the largest lava domes on Earth.^[2] It was created on the destroyed northeastern flank of now gone Mount Tehama, a stratovolcano that was at least a thousand feet (300 m) higher than Lassen. Lassen Peak As Seen From Cinder Cone (Large Version) Photograph by Brian M. McDaniel, 2003 This is a view of Lassen Peak as seen from the Cinder Cone in Lassen Volcanic Park, California. ... A topographical summit is a point on a surface which is higher in elevation than all points immediately adjacent to it. ... This article is about the U.S. state. ... For exotic financial options, see Mountain range (options). ... “Cascades” redirects here. ... In topography, prominence, also known as autonomous height, relative height or shoulder drop (in America) or prime factor (in Europe), is a concept used in the categorization of hills and mountains, also known as peaks. ... Map of Earth showing lines of latitude (horizontally) and longitude (vertically), Eckert VI projection; large version (pdf, 1. ... // Topographic maps are a variety of maps characterized by large-scale detail and quantitative representation of relief, usually using contour lines in modern mapping, but historically using a variety of methods. ... The United States Geological Survey (USGS) is a scientific agency of the United States government. ... Mountains can be characterized in several ways. ... One of the Mono Craters, an example of a rhyolite dome. ... Mariana Islands, an oceanic island arc Cascade Volcanic Arc, a continental volcanic arc A volcanic arc is a chain of volcanic islands or mountains formed by plate tectonics as an oceanic tectonic plate subducts under another tectonic plate and produces magma. ... A volcanic belt is a district of volcanoes, located in a certain area. ... There are very few or no other articles that link to this one. ... Diagram of geological time scale. ... Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station For other uses, see Volcano (disambiguation). ... Southern and northern Mount Everest climbing routes as seen from the International Space Station. ... Two hikers in the Mount Hood National Forest Eagle Creek hiking Hiking is a form of walking, undertaken with the specific purpose of exploring and enjoying the scenery. ... Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station For other uses, see Volcano (disambiguation). ... “Cascades” redirects here. ... There are very few or no other articles that link to this one. ... Mariana Islands, an oceanic island arc Cascade Volcanic Arc, a continental volcanic arc A volcanic arc is a chain of volcanic islands or mountains formed by plate tectonics as an oceanic tectonic plate subducts under another tectonic plate and produces magma. ... The Shasta Cascade region of California is located in the northeastern and north-central sections of the state bordering Oregon and Nevada, north of the Central Valley and the Sierra Nevada mountain range. ... Northern California, sometimes referred to as NorCal, is the northern portion of the U.S. state of California. ... One of the Mono Craters, an example of a rhyolite dome. ... Mount Tehama is the name given to a now destroyed volcano in the Cascades, also known as Brokeoff Volcano, centred on the Lassen volcanic center. ... A cutaway diagram of a stratovolcano Mount St. ...

Lassen Peak has the distinction of being the only other volcano in the Cascades besides Mount St. Helens to erupt during the 20th century. On May 22, 1915, an explosive eruption at Lassen Peak devastated nearby areas and rained volcanic ash as far away as 200 miles (320 km) to the east.^[2] This explosion was the most powerful in a 1914–17 series of eruptions that were the last to occur in the Cascades before the 1980 eruption of Mount St. Helens in Washington. Lassen Volcanic National Park was created in Shasta County, California to preserve the devastated area and nearby volcanic wonders. For the mountain in California, see Mount Saint Helena. ... is the 142nd day of the year (143rd in leap years) in the Gregorian calendar. ... Year 1915 (MCMXV) was a common year starting on Friday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Thursday[1] of the 13-day-slower Julian calendar). ... Ash plume from Mt Cleveland, a stratovolcano Diamond Head, a well-known backdrop to Waikiki in Hawaii, is an ash cone that solidified into tuff Volcanic ash consists of very fine rock and mineral particles less than 2 mm in diameter that are ejected from a volcanic vent. ... The 1980 eruption of Mount St. ... For the capital city of the United States, see Washington, D.C.. For other uses, see Washington (disambiguation). ... Map of Lassen area showing hydrothermal features (red dots) and volcanic feature or remnant (yellow cones). ... Shasta County is a county located in the northern portion of the U.S. state of California, in the Cascade Mountains. ...

Unlike most lava domes, Lassen is topped by craters. In fact, a series of these craters exist around Lassen's summit, although two of these are now covered by solidified lava and sulfur deposits. Lassen is the largest of a group of more than 30 volcanic domes that have erupted over the past 300,000 years in the Lassen Volcanic Center.

Climate

Lassen has the highest known snowfall amounts for California. With an average annual snowfall of 660 inches (16.76 m) , and some years receiving over 1,000 inches (25.4 m) of snow at its base of 8,250 feet (2,515 m) at Lake Helen. Mt. Lassen gets more precipitation (rain, hail, melted snow) anywhere in the Cascades south of the Three Sisters volcanoes.^[3] This heavy snowfall allows Lassen to retain 14 permanent patches of snow despite Lassen's modest elevation.^[4] Lightning has been known to frequently strike the summit of the volcano during summer thunderstorms. This page is about the form of precipitation. ... Mid-19th century tool for converting between different standards of the inch An inch is an Imperial unit of length. ... This article is about the unit of length. ... Lake Helen is a glacial lake or a tarn occupying a cirque at around 8,200 feet (2,500 m). ... This article is about the precipitation. ... The Three Sisters are three volcanic peaks of the Cascade Range, located about 15 miles SW from the nearest town of Sisters, Oregon. ... Not to be confused with lighting. ...

Geology

Further information: Lassen Volcanic National Park#Geology and Geology of the Lassen volcanic area

Vulcan's Eye on Lassen Peak from Lake Helen

Lassen is the southernmost in the chain of 18 large volcanic peaks that run from southwestern British Columbia to northern California. The peaks formed in the past 35 million years as the Juan De Fuca plate and the tiny Gorda plate to its south have been pulled under the overriding North American plate. As the oceanic crust in the Juan de Fuca plate melts under the pressure, it creates pools of lava that drive up the Cascade Range and power periodic eruptions in its volcanic peaks. Map of Lassen area showing hydrothermal features (red dots) and volcanic feature or remnant (yellow cones). ... Eruptions in the Lassen volcanic area in the last 70,000 years. ... Image File history File links Download high-resolution version (6520x3288, 8477 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Lassen Volcanic National Park Geology of the Lassen volcanic area Lassen Peak Lake Helen (Lassen Peak) ... Image File history File links Download high-resolution version (6520x3288, 8477 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Lassen Volcanic National Park Geology of the Lassen volcanic area Lassen Peak Lake Helen (Lassen Peak) ... Motto: Splendor sine occasu (Latin: Splendour without diminishment) Capital Victoria Largest city Vancouver Official languages English (de facto) Government Lieutenant-Governor Steven Point Premier Gordon Campbell (BC Liberal) Federal representation in Canadian Parliament House seats 36 Senate seats 6 Confederation July 20, 1871 (6th province) Area  Ranked 5th Total 944... A map of the Juan de Fuca Plate The Juan de Fuca Plate, named after the explorer, is a tectonic plate arising from the Juan de Fuca Ridge, and subducting under the northerly portion of the western side of the North American Plate. ... The Gorda Plate is a small oceanic tectonic plate beneath the Pacific Ocean off the coast of northern California. ...  The North American plate, shown in brown The North American Plate is a tectonic plate covering most of North America, extending eastward to the Mid-Atlantic Ridge and westward to the Cherskiy Range in East Siberia. ... Age of oceanic crust Oceanic crust is the part of Earths lithosphere that surfaces in the ocean basins. ... Look up lava, Aa, pahoehoe in Wiktionary, the free dictionary. ...

Roughly 27,000 years ago,^[2] Lassen started to form as a mound-shaped dacite lava dome pushed its way through Tehama's destroyed north-eastern flank. As the lava dome pushed its way up, it shattered overlaying rock, which formed a blanket of angular talus around the emerging steep-sided volcano (it looked much like the nearby 1,100-year-old Chaos Crags). Lassen rose and reached its present height in a relatively short time, probably in as little as a few years. Grey, red, black, altered white/tan, flow-banded pumice dacite Dacite (IPA: ) is an igneous, volcanic rock with a high iron content. ... Scree or detritic cone is a term given to broken rock that appears at the bottom of crags, mountain cliffs or valley shoulders. ... Manzanita Lake Museum Chaos Crags is the youngest volcanic plug dome in Lassen Volcanic National Park, having been formed by at least four dacite domes 1200 years ago. ...

From 25,000 to 18,000 years ago, during the last glacial period of the current ice age, Lassen’s shape was significantly altered by glacial erosion. For example, the bowl-shaped depression on the volcano’s northeastern flank, called a cirque, was eroded by a glacier that extended out 7 miles (11 km) from the dome.^[2] Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ... Severe soil erosion in a wheat field near Washington State University, USA. For erosion as an operation of Mathematical morphology, see Erosion (morphology) Erosion is displacement of solids (soil, mud, rock and other particles) by the agents of ocean currents, wind, water, or ice by downward or down-slope movement...

Lassen's most recent eruptive period started in 1914 and lasted for seven years (see below). The most powerful of these eruptions was a 1915 episode that sent ash and steam in a ten-kilometer-tall mushroom cloud, making it the largest recent eruption in the contiguous 48 U.S. states until the 1980 eruption of Mount St. Helens. The region remains geologically active, with mud pots, active fumaroles, and boiling water features, several of which are getting hotter. The area around Mount Lassen and nearby Mount Shasta are considered the most likely volcanoes in the Cascade Range to shift from dormancy to active eruptions.^[5] The 1980 eruption of Mount St. ... For the city, see Mount Shasta, California. ...

Human history

Before the arrival of white settlers, the areas surrounding Lassen Peak, especially in the east and south, were the traditional home of the (Northeastern) Maidu. The Maidu are a group of Native Americans who lived in Northern California. ...

Lassen Peak was named in honor of Danish blacksmith Peter Lassen, who guided immigrants past the peak to Sacramento Valley in the 1830s. Lassen's trail, however, never found general long-term use because it was considered unsafe. Nobles Emigrant Trail, named after William Nobles, which linked Applegate Trail in Nevada to Northern Sacramento Valley, replaced it. Peter Lassen was a Danish-American blacksmith, rancher and prospector. ... The Sacramento Valley is the portion of the California Central Valley that lies to the north of the San Joaquin-Sacramento Delta. ... William Nobles may refer to: William Nobles (guide), 1851 trail guide through Emigrant Gap in Sierra Nevada William Nobles (cinematographer) Category: ...

In 1864 Helen Tanner Brodt became the first woman to reach the summit of Lassen Peak. A tarn (lake in a cirque basin) on Lassen was named Lake Helen in her honor. Triad Lake in Glacier Peak Wilderness View of Tarn Hows, Cumbria A tarn (or corrie loch) is a mountain lake or pool, formed in a corrie excavated by a glacier. ... A cirque is an amphitheatre-like valley of glacial origin, formed by glacial erosion at the head of the glacier. ...

Starting in 1914 and ending in 1921 Lassen came alive with a series of phreatic eruptions (steam explosions), dacite lava flows, and lahars (volcanic mud flows). There were 200 to 400 volcanic eruptions during this period of activity. First-hand accounts of the time record at least one fatality, in 1915. Phreatic eruption at the summit of Mount St. ... Lahar from a March 1982 eruption of Mount St. ... This article is about volcanoes in geology. ...

Early 20th century eruptions

The "Great Explosion" eruption column of May 22, 1915 was seen as far as 150 mi (241 km) away (Photograph by R.E. Stinson)

Mount Lassen Before 1914

Lassen Peak in June 1915 with Loomis Hot Rock, one of the many large boulders set loose in the eruption that were too hot to touch for days after, in the foreground (photgraph by B.F. Loomis; modern photo)

Image File history File links May_1915_Lassen_eruption_column. ... Image File history File links May_1915_Lassen_eruption_column. ... Image File history File links Lassen_Peak_Before_1914. ... Image File history File links Lassen_Peak_Before_1914. ... Image File history File links Lassen_Peak_in_June_1915. ... Image File history File links Lassen_Peak_in_June_1915. ...

Initial rumblings (May 1914 to May 1915)

On May 30, 1914, Lassen became active again after 27,000 years dormancy when it was shaken by a steam explosion. Such steam blasts occur when molten rock (magma) rises toward the surface of a volcano and heats shallow ground water. The hot water rises under pressure through cracks and, on nearing the surface, vaporizes and vents explosively. By mid-May 1915, more than 180 steam explosions had blasted out a 1,000 ft (300 m) wide crater near the summit of Lassen Peak.^[2] is the 150th day of the year (151st in leap years) in the Gregorian calendar. ... Year 1914 (MCMXIV) was a common year starting on Thursday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Wednesday of the 13-day-slower Julian calendar). ... Magma is molten rock located beneath the surface of the Earth (or any other terrestrial planet), and which often collects in a magma chamber. ... Groundwater is any water found below the land surface. ...

Then the character of the eruption changed dramatically. On the evening of May 14, 1915, incandescent blocks of lava could be seen bouncing down the flanks of Lassen from as far away as the town of Manton, California 20 miles (30 km) to the west.^[2] By the next morning, a growing dome of dacite lava (lava containing 63 to 68% silica) had filled the volcano’s crater. May 14 is the 134th day of the year (135th in leap years) in the Gregorian calendar. ... Year 1915 (MCMXV) was a common year starting on Friday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Thursday[1] of the 13-day-slower Julian calendar). ... Look up lava, Aa, pahoehoe in Wiktionary, the free dictionary. ... Manton is a census-designated place located in Tehama County, California. ... Grey, red, black, altered white/tan, flow-banded pumice dacite Dacite (IPA: ) is an igneous, volcanic rock with a high iron content. ... The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ...

Events of May 19–20, 1915

Late on the evening of May 19, a large steam explosion fragmented the dacite dome, creating a new crater at the summit of Lassen Peak. No new magma was ejected in this explosion, but glowing blocks of hot lava from the dome fell on the summit and snow-covered upper flanks of Mount Lassen. These falling blocks launched a half mile (800 m) wide avalanche of snow and volcanic rock that roared 4 mi (6 km) down the volcano’s steep northeast flank and over a low ridge at Emigrant Pass into Hat Creek.^[2] is the 139th day of the year (140th in leap years) in the Gregorian calendar. ...

As the hot lava blocks broke into smaller fragments, the snow melted, generating a mudflow of volcanic materials, called a lahar. The bulk of this lahar was deflected northwestward at Emigrant Pass and flowed 7 miles (11 km) down Lost Creek.^[2] Even after coming to rest, both the avalanche and lahar released huge volumes of water, flooding the lower Hat Creek Valley during the early morning hours of May 20. The lahar and flood destroyed six mostly not-yet-occupied summer ranch houses. Fortunately, the few people in these houses escaped with only minor injuries. Lahar from a March 1982 eruption of Mount St. ... is the 140th day of the year (141st in leap years) in the Gregorian calendar. ...

Also during the night of May 19–20, dacite lava somewhat more fluid than that erupted on the night of May 14–15 welled up into and filled the new crater at Lassen’s summit, spilled over low spots on its rim, and flowed 1,000 feet (300 m) down the steep west and northeast flanks of the volcano.^[2]

Climactic eruption of May 22, 1915

Then at 4:30 p.m. on May 22, after two quiet days, Lassen exploded in a powerful eruption (referred to as "the Great Explosion") that blasted volcanic ash, rock fragments and pumice high into the air. This created the larger and deeper of the two craters seen near the summit of the volcano today. A huge column of volcanic ash and gas rose more than 30,000 feet (9,000 m) into the air and was visible from as far away as Eureka, California 150 miles (241 km) to the west.^[2] is the 142nd day of the year (143rd in leap years) in the Gregorian calendar. ... Motto: Eureka! - (I have found it!) Eureka shown within Humboldt County in the State of California Coordinates: , Country State County Humboldt Founded May 13, 1850 (settlement) Incorporated April 18, 1856 (town) Re-incorporated February 19, 1874 (city) Government  - Type Mayor-council  - Mayor Virginia Bass  - City manager David Tyson Area  - Total...

Pumice falling onto the northeastern slope of Lassen Peak generated a high-speed avalanche of hot ash, pumice, rock fragments, and gas, called a pyroclastic flow, that swept down the side of the volcano, devastating a 3 square miles (8 km²) area.^[2] The pyroclastic flow rapidly incorporated and melted snow in its path. The water from the melted snow transformed the flow into a highly fluid lahar that followed the path of the May 19–20 lahar and rushed nearly 10 miles (16 km) down Lost Creek to Old Station. This new lahar released a large volume of water that flooded lower Hat Creek Valley a second time. Pyroclastic flows sweep down the flanks of Mayon Volcano, Philippines, in 1984 A pyroclastic flow (also known as a pyroclastic density current) is a common and devastating result of some volcanic eruptions. ...

The powerful climactic eruption of May 22 also swept away the northeast lobe of the lava flow extruded two days earlier. The eruption produced smaller mudflows on all flanks of Lassen Peak, deposited a layer of volcanic ash and pumice traceable for 25 miles (40 km) to the northeast, and rained fine ash at least as far away as Winnemucca, Nevada, 200 miles (320 km) to the east.^[2] Together these events created the Devastated Area which is still sparsely populated by trees due to the low nutrient and high porosity of the soil there. is the 142nd day of the year (143rd in leap years) in the Gregorian calendar. ... Winnemucca cemetery with a sign reading: Welcome to Winnemucca, Proud of it! // Winnemucca is the county seat of Humboldt County in the U.S. state of Nevada and the site of a September 19, 1900 bank robbery by the Wild Bunch. ... A nutrient is a substance used in an organisms metabolism which must be taken in from the environment. ... Loess field in Germany Surface-water-gley developed in glacial till, Northern Ireland For the American hard rock band, see SOiL. For the System of a Down song, see Soil (song). ...

Later volcanic activity

For several years after the May 22, 1915, eruption, spring snowmelt percolating down into Mount Lassen triggered steam explosions, an indication that rocks beneath the volcano’s surface remained hot. Particularly vigorous steam explosions in May 1917 blasted out the second of the two craters now seen near the northwest corner of the volcano’s summit (two older craters are buried).^[2] is the 142nd day of the year (143rd in leap years) in the Gregorian calendar. ...

Steam vents could be found in the area of these craters into the 1950s but gradually waned and are difficult to locate today. Since then, the USGS in cooperation with the United States Park Service have been monitoring Lassen and other volcanic and geothermal areas in the park. The United States Geological Survey (USGS) is a scientific agency of the United States government. ... The National Park Service (NPS) is the United States government agency that deals with U.S. National Parks and U.S. National Monuments. ... Map of the geothermal areas As in many hydrothermally active areas, the rocks at Sulphur Works and Little Hot Springs Valley in Lassen Volcanic National Park have been chemically altered into bright-colored clays. ...

Deposits from May 1915 eruption of Lassen Peak (USGS map)

Image File history File links Download high-resolution version (981x677, 98 KB) USGS PD image from http://pubs. ... Image File history File links Download high-resolution version (981x677, 98 KB) USGS PD image from http://pubs. ... Image File history File links Metadata Size of this preview: 800 × 255 pixelsFull resolution (3207 × 1024 pixel, file size: 2. ...

See also

• High Cascades
• Geology of the Pacific Northwest
• Lassen Volcanic National Park
• Volcanic Legacy Scenic Byway
• List of highest points in California by county

“Cascades” redirects here. ... The Pacific Northwest region of the United States is still geologically active. ... Map of Lassen area showing hydrothermal features (red dots) and volcanic feature or remnant (yellow cones). ... The Volcanic Legacy Scenic Byway is an All-American Road in California and Oregon. ...

References

Major works cited

• Geology of National Parks: Fifth Edition, Ann G. Harris, Esther Tuttle, Sherwood D., Tuttle (Iowa, Kendall/Hunt Publishing; 1997) ISBN 0-7872-5353-7
• EO Newsroom (NASA), New Images of Lassen Volcanic National Park (adapted public domain text; accessed 18 September 2006)
• Eruptions of Lassen Peak, California, 1914 to 1917, U.S. Geological Survey Fact Sheet 173-98 (adapted public domain text; accessed 18 September 2006)

is the 261st day of the year (262nd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 261st day of the year (262nd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ...

Notes

is the 4th day of the year in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ...

External links

• The Official Lassen Volcanic National Park Web Site
• USGS: Eruptions of Lassen Peak, California, 1914 to 1917

• Smithsonian Institution Global Volcanism Program: Lassen Peak

• Lassen Peak is at coordinates 40°29′17″N 121°30′18″W / 40.48817, -121.50501 (Lassen Peak)Coordinates: 40°29′17″N 121°30′18″W / 40.48817, -121.50501 (Lassen Peak)

v • d • e Major Cascade Volcanoes
British Columbia	Mount Silverthrone · Silverthrone Caldera · Plinth Peak · Mount Meager · Mount Cayley · Mount Garibaldi
Washington	Mount Baker · Glacier Peak · Mount Rainier · Mount St. Helens · Mount Adams
Oregon	Mount Hood · Mount Jefferson · Three Sisters · Broken Top · Mount Bachelor · Newberry Volcano · Mount Thielsen · Mount Mazama (Crater Lake) · Mount McLoughlin
California	Medicine Lake Volcano · Mount Shasta · Shastina · Mount Tehama · Lassen Peak