Lassen Volcanic Center

Photo of this volcano
  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 40.492°N
  • 121.508°W

  • 3187 m
    10453 ft

  • 323080
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number

Most Recent Bulletin Report: June 1992 (BGVN 17:06) Citation IconCite this Report


Seismicity apparently triggered by M 7.5 earthquake hundreds of kilometers away

Southern California's largest earthquake since 1952, M 7.5 on 28 June, appeared to trigger seismicity at several volcanic centers in California. It was centered roughly 200 km E of Los Angeles. In the following, David Hill describes post-earthquake activity at Long Valley caldera, and Stephen Walter discusses the USGS's seismic network, and the changes it detected at Lassen, Shasta, Medicine Lake, and the Geysers.

In recent years, the USGS northern California seismic network has relied upon Real-Time Processors (RTPs) to detect, record, and locate earthquakes. However, a film recorder (develocorder) collects data from 18 stations in volcanic areas, primarily to detect long-period earthquakes missed by RTPs. The film recorders proved useful in counting the post-M 7.5 earthquakes, most of which were too small to trigger the RTPs.

The film record was scanned for the 24 hours after the M 7.5 earthquake, noting the average coda duration for each identified event. Some events may have been missed because of seismogram saturation by the M 7.5 earthquake. Marked increases in microseismicity were observed at Lassen Peak, Medicine Lake caldera, and the Geysers (table 1). No earthquakes were observed at Shasta, but the lack of operating stations on the volcano limited the capability to observe small events.

Table 1. Number of earthquakes at northern California volcanic centers during 24-hour periods following major earthquakes on 25 April (40.37°N, 124.32°W; M 7.0) and 28 June (34.18°N, 116.47°W; M 7.5) 1992. Events with coda durations less than or equal to 10 seconds and greater than 10 seconds are tallied separately. Earthquakes were identified from film records of seismograms from nearby stations. Courtesy of Stephen Walter.

Date Lassen Shasta Medicine Lake Geysers
Codas (seconds) <=10 >10 <=10 >10 <=10 >10 <=10 >10
25 Apr 1992 0 0 0 1 0 0 7 2
28 Jun 1992 8 14 1 5 12 0 46 4

Film was also scanned for the 24 hours following the M 7.0 earthquake at 40.37°N, 124.32°W (near Cape Mendocino) on 25 April. Although smaller than the 28 June earthquake, its epicenter was only 20-25% as far from the volcanoes. Furthermore, both the 25 April main shock and a M 6.5 aftershock were felt at the volcanic centers, but no felt reports were received from these areas after the 28 June earthquake. Only the Geysers showed any possible triggered events after the 25 April shock. However, background seismicity at the Geysers is higher than at the other centers, and is influenced by fluid injection and withdrawal associated with intensive geothermal development.

Lassen Report.Of the three major Holocene volcanoes in the California Cascades, Lassen (~800 km NNW of the epicenter) had the strongest response to the 28 June earthquake (figure 1). About 10 minutes after the S-wave's arrival and while surface waves were still being recorded, a M 2.8 event occurred south of Lassen Peak. Film records showed 9 more earthquakes in the first hour, and 22 events were identified during the first 24 hours. Although most were M 1 or smaller, at least two and perhaps as many as four were of magnitude greater than or equal to 2. Nine were detected by the RTP system. The best preliminary locations were concentrated ~3 km SW of Lassen Peak at

Figure (see Caption) Figure 1. Seismic events in the Lassen area that were apparently triggered by the M 7.5 southern California earthquake of 28 June 1992 (circles) compared to 1978-90 seismicity in the region (crosses). Squares mark seismic stations. Courtesy of S. Walter.

Information Contacts: Stephen Walter and David Hill, MS 977, U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 USA.

The Global Volcanism Program has no Weekly Reports available for Lassen Volcanic Center.

Bulletin Reports - Index


Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.

06/1992 (BGVN 17:06) Seismicity apparently triggered by M 7.5 earthquake hundreds of kilometers away




Information is preliminary and subject to change. All times are local (unless otherwise noted)


June 1992 (BGVN 17:06) Citation IconCite this Report


Seismicity apparently triggered by M 7.5 earthquake hundreds of kilometers away

Southern California's largest earthquake since 1952, M 7.5 on 28 June, appeared to trigger seismicity at several volcanic centers in California. It was centered roughly 200 km E of Los Angeles. In the following, David Hill describes post-earthquake activity at Long Valley caldera, and Stephen Walter discusses the USGS's seismic network, and the changes it detected at Lassen, Shasta, Medicine Lake, and the Geysers.

In recent years, the USGS northern California seismic network has relied upon Real-Time Processors (RTPs) to detect, record, and locate earthquakes. However, a film recorder (develocorder) collects data from 18 stations in volcanic areas, primarily to detect long-period earthquakes missed by RTPs. The film recorders proved useful in counting the post-M 7.5 earthquakes, most of which were too small to trigger the RTPs.

The film record was scanned for the 24 hours after the M 7.5 earthquake, noting the average coda duration for each identified event. Some events may have been missed because of seismogram saturation by the M 7.5 earthquake. Marked increases in microseismicity were observed at Lassen Peak, Medicine Lake caldera, and the Geysers (table 1). No earthquakes were observed at Shasta, but the lack of operating stations on the volcano limited the capability to observe small events.

Table 1. Number of earthquakes at northern California volcanic centers during 24-hour periods following major earthquakes on 25 April (40.37°N, 124.32°W; M 7.0) and 28 June (34.18°N, 116.47°W; M 7.5) 1992. Events with coda durations less than or equal to 10 seconds and greater than 10 seconds are tallied separately. Earthquakes were identified from film records of seismograms from nearby stations. Courtesy of Stephen Walter.

Date Lassen Shasta Medicine Lake Geysers
Codas (seconds) <=10 >10 <=10 >10 <=10 >10 <=10 >10
25 Apr 1992 0 0 0 1 0 0 7 2
28 Jun 1992 8 14 1 5 12 0 46 4

Film was also scanned for the 24 hours following the M 7.0 earthquake at 40.37°N, 124.32°W (near Cape Mendocino) on 25 April. Although smaller than the 28 June earthquake, its epicenter was only 20-25% as far from the volcanoes. Furthermore, both the 25 April main shock and a M 6.5 aftershock were felt at the volcanic centers, but no felt reports were received from these areas after the 28 June earthquake. Only the Geysers showed any possible triggered events after the 25 April shock. However, background seismicity at the Geysers is higher than at the other centers, and is influenced by fluid injection and withdrawal associated with intensive geothermal development.

Lassen Report.Of the three major Holocene volcanoes in the California Cascades, Lassen (~800 km NNW of the epicenter) had the strongest response to the 28 June earthquake (figure 1). About 10 minutes after the S-wave's arrival and while surface waves were still being recorded, a M 2.8 event occurred south of Lassen Peak. Film records showed 9 more earthquakes in the first hour, and 22 events were identified during the first 24 hours. Although most were M 1 or smaller, at least two and perhaps as many as four were of magnitude greater than or equal to 2. Nine were detected by the RTP system. The best preliminary locations were concentrated ~3 km SW of Lassen Peak at

Figure (see Caption) Figure 1. Seismic events in the Lassen area that were apparently triggered by the M 7.5 southern California earthquake of 28 June 1992 (circles) compared to 1978-90 seismicity in the region (crosses). Squares mark seismic stations. Courtesy of S. Walter.

Information Contacts: Stephen Walter and David Hill, MS 977, U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 USA.

Eruptive History


Summary of Holocene eruption dates and Volcanic Explosivity Indices (VEI).


Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
1914 May 30 1917 Jun 29 Confirmed 3 Historical Observations Lassen Peak
[ 1850 Aug ] [ 1851 ] Discredited    
1666 (?) Unknown Confirmed 3 Dendrochronology Cinder Cone
[ 1650 (?) ] [ Unknown ] Uncertain     Chaos Crags
0980 ± 300 years Unknown Confirmed   Radiocarbon (corrected) Chaos Crags
0880 ± 300 years Unknown Confirmed   Radiocarbon (corrected) Chaos Crags
0800 ± 300 years Unknown Confirmed   Radiocarbon (corrected) Chaos Crags

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.

Photo Gallery


The blocky surface of Chaos Jumbles in the foreground was produced by collapse of a portion of the Chaos Crags lava dome complex in the background about 1650 CE. The cold rock avalanche traveled 5 km from its source, and may have occurred in the absence of any eruptive activity. Three successive lobes of the avalanche cover an area of 8 sq km.

Photo by Lee Siebert, 1982 (Smithsonian Institution).
See title for photo information.
The tree stump and strip of red bark fragments in the foreground are the remnants of one of the many trees blown down radially away from the volcano by a pyroclastic surge on May 22, 1915, during the paroxysmal phase of the 1914-1917 eruption of Lassen Peak. The Devastated Area in the background remained sparsely vegetated for many decades following the eruption.

Photo by Lee Siebert, 1982 (Smithsonian Institution).
See title for photo information.
The trunks of the large ponderosa pine tree at the left and the smaller birch to the right in the Lost Creek valley NE of Lassen Peak were bent over by a mudflow from an eruption in May 1915. After the eruption vertical growth of the trees resumed. The mudflows traveled 50 km from the volcano, destroying bridges, farmlands, and farm buildings.

Photo by Lee Siebert, 1982 (Smithsonian Institution).
See title for photo information.
Chaos Jumbles, a debris avalanche-deposit formed by collapse of Chaos Crags about 1650 CE, is seen from the top of the avalanche scarp. The avalanche traveled up to 5 km in three lobes now covered with varying degrees of vegetation. The avalanche was emplaced as a cold rockfall avalanche; there is no direct evidence for an associated explosive eruption.

Photo by Lee Siebert, 1982 (Smithsonian Institution).
See title for photo information.
The massive dacitic lava dome of Lassen Peak rises above Lake Helen on the south side of the volcano. Plugs of dark dacitic lava exposed near the summit are surrounded by vast aprons of lighter-colored talus associated with growth of the lava dome.

Photo by Lee Siebert, 1972 (Smithsonian Institution).
See title for photo information.
Hikers perch on a small pinnacle of dacitic lava that forms the high point of Lassen Peak, the southernmost major volcano in the Cascade Range that stretches from southern British Columbia to northern California. Lassen Peak is a large dacitic lava dome that last erupted from 1914 to 1917.

Photo by Lee Siebert, 1968 (Smithsonian Institution).
See title for photo information.
An aerial view of cloud-capped Lassen Peak from the NW shows the Chaos Crags lava dome complex on its left, the source of rockfall avalanche in 1650 CE, and the older Brokeoff stratovolcano and post-caldera lava domes on the right. Lassen Peak was the source of California's latest eruption, that lasted from 1914 to 1917.

Photo by Lyn Topinka, 1984 (U.S. Geological Survey).
See title for photo information.
The sparsely vegetated Devastated Zone on the NE flank of Lassen Peak was swept by a pyroclastic surge on May 22, 1915, during the paroxysmal phase of the 1914-1917 eruption. The pyroclastic surge destroyed forests, and was accompanied by mudflows that traveled down Lost Creek and Hat Creek valleys.

Photo by Lyn Topinka, 1984 (U.S. Geological Survey).
See title for photo information.
U.S. Geological Survey volcanologists conduct Electronic Distance Measurement surveys NW of Lassen Peak as part of a monitoring program at Lassen volcano. Chaos Crags lava dome rises in the background. The large scarp at the left was formed during collapse of part of Chaos Crags about 1650 CE.

Photo by Lyn Topinka, 1984 (U.S. Geological Survey).
See title for photo information.
Lassen Peak, rising above Manzanita Lake on the NW, is the focal point of the Lassen volcanic center, a concentration of volcanic features covering much of Lassen National Park. The massive lava dome forming Lassen Peak was constructed about 25,000 years ago and was the site of California's most recent eruption during 1914-1917. Chaos Crags, a lava dome complex on the north flank, and the aptly named Cinder Cone to the NE, have also erupted within the past 1200 years.

Photo by Dave Wieprecht, 1995 (U.S. Geological Survey).
See title for photo information.
Lassen Peak rises in the background behind the Chaos Crags, a group of dacitic lava domes on Lassen's north flank. The Chaos Crags were formed during a series of eruptions about 1100 to 1000 years ago in which early explosive eruptions and pyroclastic flows were followed by growth of a complex of five lava domes. The area of light-colored talus on the right side is the source of a large debris avalanche from Chaos Crags about 1650 CE.

Photo by Dan Dzurisin, 1982 (U.S. Geological Survey).
See title for photo information.
Chaos Crags in the foreground and Lassen Peak in the background are large lava dome complexes in the southern Cascade Range. Chaos Crags consists of a group of five overlapping dacitic lava domes that were erupted a little over 1000 years ago. Lassen Peak was formed about 25,000 years ago, but last erupted during 1914-17.

Photo by Dan Dzurisin, 1982 (U.S. Geological Survey).
See title for photo information.
The Chaos Crags lava dome complex on the north flank of Lassen Peak, seen here from the south, was formed at the end of an eruptive period about 1100-1000 years ago. A tephra ring from associated explosive eruptions forms the light-colroed area at the middle right.

Photo by Dan Dzurisin, 1981 (U.S. Geological Survey).
See title for photo information.
The Devastated Area swept by pyroclastic surges during an explosion on May 22, 1915 is seen here from the NE flank of Lassen Peak. The May 22 produced an eruption plume as high as 9 km, a pyroclastic surge that swept the area seen here, and a series of three lahars, the two largest of which swept down Lost Creek to the NE. The area as far as the distant flank of forested Raker Peak at the upper left was affected by the May 22 pyroclastic surge. Revegetation has begun to cover the distal parts of the May 1915 deposits.

Photo by Bill Chadwick, 1981 (U.S. Geological Survey).
See title for photo information.
Lassen Peak, seen from Brokeoff volcano to the SW, is one of a series of dacitic lava domes erupted during the past 25,000 years along the northern edge of a caldera on the northern flank of Brokeoff volcano. Lassen Peak is the largest and most recently active of these domes.

Photo by Bill Chadwick, 1981 (U.S. Geological Survey).
See title for photo information.
The summit of Lassen Peak contains a blocky lava flow in the center and several craters formed during the 1914-1917 eruption. Lava flows spilled through low notches in the east and west crater rims. The crater in the right foreground, on the NW side of the summit, was formed as a result of explosions near the end of the eruption in 1917.

Photo by Bill Chadwick, 1981 (U.S. Geological Survey).
See title for photo information.
In May, 1915, a year after the start of the eruption, two blocky lava flows spilled through gaps in the eastern and western crater rims and descended the upper flanks of the volcano. The western flow, seen here, traveled about 500 m down the flank; on May 19, 1915, the eastern flow fragmented and mixed with snowmelt, forming a mudflow that traveled 35 km down Lost Creek and Hat Creek valleys, destroying bridges and farm buildings.

Photo by Bill Chadwick, 1981 (U.S. Geological Survey).
See title for photo information.
Snow-capped Lassen Peak is seen here from the summit of Prospect Peak shield volcano at the NE end of Lassen Volcanic National Park. The unvegetated, largely snow-free peaks on the right horizon are the Chaos Crags, a complex of dacitic lava domes last active about 1100 years ago. The Twin Lakes sequence of andesitic lava shields and cones forms the lake-studded area of the Central Plateau in the center of the photo.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
See title for photo information.
The aptly named Cinder Cone, a symmetrical pyroclastic cone at the NE end of the Lassen volcanic center, is seen here from the NE across Butte Lake. The unvegetated lava flow at the left originated from the cone. Although there is a report of an eruption from Cinder Cone in 1850 CE, recent work suggests that the cone and associated lava flows all formed during a brief eruptive interval lasting at most a few decades about 230-425 radiocarbon years ago. Lava flows traveled to the NE and SE, forming Snag Lake and Butte Lake.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
See title for photo information.
Butte Lake in NE Lassen Volcanic National Park was formed when the blocky lava flow seen across the lake dammed local drainages. The flow was one of five accompanying the eruption that formed Cinder Cone several hundred years ago. This marks the NW-most extent of lava flows from Cinder Cone.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
See title for photo information.
The unvegetated pyroclastic cone in the foreground, seen from near the summit of Prospect Peak, is Cinder Cone in NE Lassen Volcanic National Park. Cinder Cone, which was formed during an eruption several hundred years ago, was the source of an extensive series of lava flows that can be seen on the far side of the cone. The flows dammed up local drainages, forming two lakes, one of which is Snag Lake, seen here SSE of the cone.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
See title for photo information.
Lava flows traveled about 3.5 km to the north and south from Cinder Cone, blocking drainages and forming two lakes. The northern lake, Butte Lake, is seen here from the summit of Cinder Cone. The quartz-bearing basaltic lava flows originated from vents at the SE flank of the pyroclastic cone. The old Emigrant Trail connecting Nevada with the Sacremento Valley winds through the trees at the left base of the cone.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
See title for photo information.
A series of lava flows from a vent on the SE flank of Cinder Cone traveled about 3.5 km to the north and south. Snag Lake, seen here to the south from the summit of Cinder Cone, was formed with the lava flow dammed up drainages. The colorful area at the lower left, known as the Painted Dunes, is an ash deposit oxidized by the heat of a still-hot underlying lava flow. The dark-colored main flow beyond the Painted Dunes was emplaced later during the same eruption, and is ash free.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
See title for photo information.
The summit of Cinder Cone contains nested craters with several crater rims created as a result of changes in vent location and eruption intensity. The scoria cone was formed during eruptions several hundred years ago in NE Lassen Volcanic National Park. Prospect Peak, an andesitic shield volcano capped by a small pyroclastic cone, is the forested peak in the background NW of Cinder Cone.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
See title for photo information.
The colorful Painted Dunes at Cinder Cone in NE Lassen Volcanic National Park were formed when ash deposits from Cinder Cone were oxidized by a still-hot underlying lava flow. The mounded surface of the ash reflects the irregular topography of the underlying Painted Dunes lava flow. A black ash-free lava flow, also erupted from Cinder Cone at a later date during the same eruption, can be seen at the top of the photo.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
See title for photo information.
A roughly 3-m-high rounded glacial erratic at the Bumpass Hell parking lot is witness to the extensive glacial erosion that has affected much of Lassen Volcanic National Park. Brokeoff volcano in the background is the glacially eroded remnant of a large stratovolcano that formed begining about 600,000 years ago. At its peak the volcano may have reached a height of 3350 m. Glacial erosion of hydrothermally altered rocks at the core of the volcano has produced a large central depression.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
See title for photo information.
This view from Prospect Peak shows perhaps the youngest lava flow immediately north of the Lassen volcanic center. This sparsely vegetated flow originated from a small cinder cone (left-center) between Prospect and West Prospect (upper left) peaks, two young basaltic lava cones straddling the NE border of Lassen Volcanic National Park. The young, but undated andesitic flow traveled initially to the NE and then around the flank of West Prospect Peak to the NW.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
See title for photo information.

Smithsonian Sample Collections Database


The following 64 samples associated with this volcano can be found in the Smithsonian's NMNH Department of Mineral Sciences collections. Catalog number links will open a window with more information.

Catalog Number Sample Description
NMNH 111123-101 Quartz basalt
NMNH 111123-101 Quartz basalt
NMNH 111123-1242 "Basalt with augite, iddingsite, and others"
NMNH 111123-1426 Dacite
NMNH 111123-1427 "Dacite with augite, biotite, and others"
NMNH 111123-1428 "Dacite with apatite, biotite, and others"
NMNH 111123-1429 Dacite
NMNH 111123-1430 Dacite
NMNH 111123-1431 Dacite
NMNH 111123-1445 Hypersthene andesite
NMNH 111123-1449 Quartz basalt
NMNH 111123-1450 Basalt
NMNH 111123-791 Quartz basalt
NMNH 111123-792 Quartz basalt
NMNH 111123-793 Pumice with glass and plagioclase
NMNH 111123-794 Quartz basalt
NMNH 111123-795 "Quartz basalt with glass, globulite, and others"
NMNH 111123-796 "Quartz basalt with augite, glass, and others"
NMNH 111123-82 Dacite
NMNH 111123-82 Dacite
NMNH 111123-95 Tuffaceous-sand
NMNH 111123-95 Volcanic sand
NMNH 111123-96 Tephra
NMNH 112407 Andesite-dacite
NMNH 113619-4 Gypsum
NMNH 113619-5 Mirabilite
NMNH 113619-6 Volcanic ash
NMNH 113619-7 Sulphur
NMNH 114901 Volcanic dust
NMNH 115559-1 Andesite-dacite
NMNH 116137-1 Pumice
NMNH 116137-2 Dacite
NMNH 116137-3 Banded dacite
NMNH 116465 Andesite-dacite
NMNH 2072 Quartz basalt
NMNH 22923 Volcanic cinder
NMNH 22926 Basalt
NMNH 38364 Perlite
NMNH 38604 Quartz basalt
NMNH 70589 Quartz basalt
NMNH 70597 Dacite
NMNH 70598 Quartz basalt
NMNH 91416 Dacite
NMNH 91417 Dacite
NMNH 91419 Dacite
NMNH 91420 Dacite
NMNH 91421 Dacite
NMNH 91422 Dacite volcanic breccia
NMNH 91425 Dacite
NMNH 91426 Lava
NMNH 91430 Volcanically scorched pine needles
NMNH 91431 Volcanic dust
NMNH 91433-1 Dacite
NMNH 91433-10 Basalt
NMNH 91433-11 Hornblende andesite
NMNH 91433-12 Alunite
NMNH 91433-2 Dacite
NMNH 91433-3 Dacite
NMNH 91433-4 Dacite
NMNH 91433-5 Rhyolite glass
NMNH 91433-6 Rhyolite
NMNH 91433-7 Andesite
NMNH 91433-8 Andesite
NMNH 91433-9 Alunite rock

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