Medicine Lake

Photo of this volcano
Google Earth icon
  Google Earth Placemark
  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 41.611°N
  • 121.554°W

  • 2412 m
    7911 ft

  • 323020
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number

The Global Volcanism Program has no activity reports for Medicine Lake.

The Global Volcanism Program has no Weekly Reports available for Medicine Lake.

Index of Monthly Reports

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.

09/1988 (SEAN 13:09) Earthquake swarm but no inflation

10/1988 (SEAN 13:10) Occasional seismicity; caldera subsides

11/1988 (SEAN 13:11) Small seismic swarm

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


Contents of Monthly Reports

All information contained in these reports is preliminary and subject to change.

All times are local (= UTC - 8 hours)

09/1988 (SEAN 13:09) Earthquake swarm but no inflation

The quoted material is a report from Steve Walter.

"On 29 September, 47 earthquakes were detected at Medicine Lake volcano, a large shield (50 km E of Mt. Shasta) that has experienced only 1 earthquake in the past eight years. The largest event (M 3.1) was located in the SW region of the caldera at a depth of 3.3 km (figure 1). Activity increased on 30 September when a total of 146 earthquakes were registered, 66 during a l-hour period. Four of these events (largest M 4.1) were located near the 29 September earthquake. After 30 September, seismicity declined to ~10 events/day until 4 October when there were 33 events, including a M 3.1 earthquake. Activity again declined with sporadic events (up to 5/day, M <2.0) continuing through 16 October. Most of the seismicity was recorded on the nearest instrument at Little Mt. Hoffman, ~4 km W of the epicentral zone. The next nearest stations are over 30 km from Medicine Lake in the Mt. Shasta network. On 3 October, a station was removed from the Mt. Shasta net and established at Medicine Mountain, ~1 km S of the epicentral zone on the S rim of the caldera. Although seismicity has declined, the USGS has selected six sites around the caldera for installation of one 3-component, low-gain, and six 1-component seismometers, scheduled for late October."

Figure 1. Map showing geologic features, earthquake locations (M 3.1), and the road where the levelling survey was conducted. Filled circles are late September-early October events reported in BGVN 13:09. Open circles are post-29 October events. The M 2.0 event is ESE of Medicine Lake Glass Flow. Triangles represent three of the six new sites installed 22 October. LMD is a 3-component site.Epicenter locations courtesy of Steve Walter.

A levelling line, measured along the main caldera access road (figure 1) by Dan Dzurisin in August 1988, indicated at least 18 cm of deflation relative to a 1954 survey. Re-measurements of the same line in early October showed little or no additional deformation. Dzurisin and Phil Dawson attributed recent ground cracks, outside of the epicentral area and circumferential to Little Medicine Lake, as slumping possibly caused by the seismicity. No cracks were observed within the epicentral area, but recent tree falls were evident. Pre-existing weak fumarolic activity had not changed, although not all fumarolic areas were visited.

Information Contacts: S. Walter, USGS Menlo Park; D. Dzurisin, CVO.

10/1988 (SEAN 13:10) Occasional seismicity; caldera subsides

"Seismicity ... continued sporadically throughout October. As of 15 November, seismicity had declined to several locatable events/week. Most were of M <1 with the exception of a M 2 event on 29 October. The installation of a tightly spaced seismic network on 22 October permits even small events to be located. Three well-constrained earthquakes have been located since 29 October in the E, central, and S portions of Medicine Lake glass flow in the NW part of the caldera (figure 1). Depths of recent events are shallow, between 0.5 and 1.5 km. The locations of the recent events show a northward shift from those of the late September swarm. Seismologists are uncertain whether this shift is real or the result of improved locations from the new network."

A levelling line (~16 benchmarks spaced 1.5-2.25 km apart along the main caldera access road through the W, center, and SE portions of the caldera) was reoccupied on three occasions. Relative to a 1954 National Geodetic Survey, August 1988 measurements showed 175 ± 11 mm of central caldera subsidence with respect to the W and S rims, although subsidence extended outside the caldera. An October 1988 survey indicated 8 ± 5 mm of additional subsidence which is within 2-3 standard errors of noise levels. However, the shapes of the long- and short-term deformation curves are similar, with maximum subsidence occurring at the central caldera benchmark, suggesting to geologists that the deformation is real. The line will be relevelled in the spring when snow conditions permit.

Information Contacts: S. Walter, USGS Menlo Park; D. Dzurisin, CVO.

11/1988 (SEAN 13:11) Small seismic swarm

Small events recorded late November-early December were attributed to freezing phenomena as winter came to N California. On 13 December at 2035, an M 1.9 earthquake, ~0.25 km SW of Medicine Lake glass flow, was recorded. During the next 75 minutes, nine events (M <1.9) were detected, followed by seven events on 14 December from 0121 to 0129. Seismicity was shallow (<1 km) and had a high-frequency character. The 3-component station (LMD) is not currently operating.

Information Contacts: S. Walter, USGS Menlo Park.

06/1992 (BGVN 17:06) 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.

                        Lassen       Shasta   Medicine Lake    Geysers
    Codas (seconds)   <=10  >10    <=10  >10    <=10  >10     <=10  >10
    25 April             0    0       0    1       0    0        7    2
    28 June              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.

Medicine Lake Report. Twelve events were detected in the Medicine Lake area (~900 km NNW of the epicenter) in the 30 minutes after the M 7.5 earthquake. All had coda durations less than or equal to 10 seconds. The lack of any S-P separation indicated that they were centered very close to the single seismic station, near the center of the caldera. All known historical seismicity had occurred in the central caldera as part of a mainshock/aftershock sequence during the fall and winter of 1988-89.

Information Contacts: S. Walter and D. Hill, USGS Menlo Park.

Medicine Lake is a large Pleistocene-to-Holocene, basaltic-to-rhyolitic shield volcano east of the main axis of the Cascade Range. Medicine Lake volcanism, similar in style to that of Newberry volcano in Oregon, began less than one million years ago. A roughly 7 x 12 km caldera truncating the summit contains a lake that gives the volcano its name. A series of young eruptions lasting a few hundred years began about 10,500 years before present (BP) and produced 5 cu km of basaltic lava. Eruptive activity resumed 6000 years later, producing a chemically varied group of basaltic lava flows from flank vents and silicic obsidian flows from vents within the caldera and on the upper flanks. The last eruption produced the massive Glass Mountain obsidian flow on the east flank about 900 years BP. Lava Beds National Monument on the northern flank of Medicine Lake shield volcano contains hundreds of lava-tube caves displaying a variety of spectacular lava-flow features, most of which are found in the voluminous Mammoth Crater lava flow, which extends in several lobes up to 24 km from the vent.

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

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
[ 1910 Jan ] [ Unknown ] Uncertain 1   East flank (Glass Mountain ?)
1080 ± 25 years Unknown Confirmed 3 Magnetism Upper east flank (Glass Mountain)
0890 ± 100 years Unknown Confirmed 3 Radiocarbon (uncorrected) SW flank (Little Glass Mountain)
0830 ± 25 years Unknown Confirmed   Tephrochronology SW flank (Paint Pot Crater)
0800 (?) Unknown Confirmed   Magnetism North flank, Callahan lava flow
0720 (?) Unknown Confirmed   Magnetism NE caldera rim (Mt. Hoffman area)
0050 BCE (?) Unknown Confirmed 0 Magnetism NW caldera floor (Medicine lava flow)
0780 BCE ± 100 years Unknown Confirmed   Radiocarbon (uncorrected) SE flank, Burnt Lava flow
1080 BCE ± 50 years Unknown Confirmed 0 Radiocarbon (uncorrected) Lower north flank (Black Crater)
2410 BCE ± 100 years Unknown Confirmed   Radiocarbon (uncorrected) SE caldera rim

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.



Synonyms
Modoc-Medicine Lake Field | Medicine Lake Highland


Cones
Feature Name Feature Type Elevation Latitude Longitude
Badger Peak Cone 2241 m 41° 36' 0" N 121° 38' 0" W
Bearpaw Butte Cone 1628 m 41° 43' 0" N 121° 33' 0" W
Big Sand Butte Cone 41° 42' 0" N 121° 25' 0" W
Black Mountain Cone 2135 m 41° 32' 0" N 121° 29' 0" W
Bonita Butte Cone 1526 m 41° 44' 0" N 121° 40' 0" W
Border Mountain Cone 1912 m 41° 30' 0" N 121° 28' 0" W
Buck Butte Cone 41° 28' 0" N 121° 28' 0" W
Caldwell Butte Cone 1582 m 41° 42' 0" N 121° 29' 0" W
Cinder Butte Cone 1885 m 41° 41' 0" N 121° 36' 0" W
Cinder Cone Cinder cone 1927 m 41° 32' 0" N 121° 39' 0" W
Cougar Butte Cone 41° 39' 0" N 121° 28' 0" W
Crescent Butte Cone 1524 m 41° 43' 0" N 121° 31' 0" W
Doe Peak Cone 1875 m 41° 30' 0" N 121° 45' 0" W
East Sand Butte Cone 41° 41' 0" N 121° 23' 0" W
Fourmile Hill Cone 2153 m 41° 39' 0" N 121° 37' 0" W
Hardin Butte Cone 1347 m 41° 46' 0" N 121° 32' 0" W
Hippo Butte Cone 1674 m 41° 43' 0" N 121° 32' 0" W
Indian Butte Cone 2078 m 41° 38' 0" N 121° 30' 0" W
Little Mount Hoffman Cone 2235 m 41° 35' 0" N 121° 39' 0" W
Little Sand Butte Cone 41° 40' 0" N 121° 25' 0" W
Lookout Butte Cone 1969 m 41° 39' 0" N 121° 37' 0" W
Lyons Peak Cone 2409 m 41° 35' 0" N 121° 30' 0" W
Papoose Hill Cone 1792 m 41° 30' 0" N 121° 39' 0" W
Powder Hill Cone 1744 m 41° 29' 0" N 121° 38' 0" W
Pumice Stone Mountain Cone 2126 m 41° 34' 0" N 121° 43' 0" W
Red Cap Mountain Cone 2146 m 41° 33' 0" N 121° 45' 0" W
Red Hill Cone 1978 m 41° 33' 0" N 121° 39' 0" W
Red Shale Butte Cone 2377 m 41° 35' 0" N 121° 32' 0" W
Schonchin Butte Cinder cone 1601 m 41° 44' 0" N 121° 32' 0" W
Shotgun Peak Cone 2025 m 41° 32' 0" N 121° 33' 0" W
Six Shooter Butte Cone 1945 m 41° 31' 0" N 121° 37' 0" W
Snag Hill Cone 1727 m 41° 28' 0" N 121° 39' 0" W
Three Sisters Cone 1614 m 41° 43' 0" N 121° 44' 0" W
Whitney Butte Cone 1525 m 41° 44' 0" N 121° 35' 0" W


Craters
Feature Name Feature Type Elevation Latitude Longitude
Burnt Lava Flow Crater - Cone 41° 31' 0" N 121° 32' 0" W
Deep Crater Crater - Cone 41° 27' 0" N 121° 33' 0" W
Double Hole Crater Crater
Giant Crater Crater 1743 m 41° 30' 0" N 121° 38' 0" W
High Hole Crater Crater - Cone 1885 m 41° 31' 0" N 121° 32' 0" W
Mammoth Crater Crater 1615 m 41° 42' 0" N 121° 33' 0" W
Paint Pot Crater Crater 1926 m 41° 33' 0" N 121° 42' 0" W
Semi Crater Crater 1420 m 41° 45' 0" N 121° 32' 0" W


Domes
Feature Name Feature Type Elevation Latitude Longitude
Glass Mountain
    Big Glass Mountain
Dome 2331 m 41° 36' 0" N 121° 30' 0" W
Hoffman, Mount Dome 2412 m 41° 37' 0" N 121° 33' 0" W
Little Glass Mountain
    Stone Mountain
Dome 2089 m 41° 34' 0" N 121° 41' 0" W
The Little Glass Mountain obsidian flow, seen from Little Mount Hoffman on the west rim of Medicine Lake caldera with Mount Shasta in the background, was erupted on the SW flank of Medicine Lake volcano a little more than 1000 years ago. The light-colored rounded peak in line with Mount Shasta is Pumice Stone Mountain, which is overlain by pumice from the Little Glass Mountain eruption. A series of smaller flows to the NE known as the Crater Glass Flows were erupted at about the same time.

Photo by Lee Siebert, 1981 (Smithsonian Institution).
The summit of Schonchin Butte in Lava Beds National Monument provides a view of step-like Basin-and-Range faulting to the NW. The dark lava flow at the base of the closest scarp is the late-Pleistocene Devils Homestead lava flow. The two thin black streaks in front of the Devils Homestead flow are 3000-year-old lava flows from fissures at Black Crater and Ross Chimneys.

Photo by Lee Siebert, 1981 (Smithsonian Institution).
Schonchin Butte, a late-Pleistocene cinder cone on the north flank of Medicine Lake volcano, is one of the most prominent landmarks of Lava Beds National Monument. A large number of lava tubes in the area fed late-Pleistocene and Holocene lava flows and are accessible to monument visitors.

Photo by Lee Siebert, 1981 (Smithsonian Institution).
The massive Medicine Lake volcano in NE California, seen here from the NE, is a 50-km-wide shield volcano that is truncated by a 7 x 11 km wide caldera. During the Holocene, obsidian flows have been erupted from summit and flank vents, and voluminous basaltic lava flows have erupted from vents on the north and south flanks. The latest eruptions of Medicine Lake volcano took place about 1000 years ago.

Photo by Julie Donnely-Nolan, 1982 (U.S. Geological Survey).
High Hole Crater, a cinder cone on the SE flank of Medicine Lake volcano, was the source of a large, youthful-looking lava flow that was erupted about 2700 years ago. The lava flow, the largest from Medicine Lake during the Holocene, covered 37 sq km and had a volume of 0.45 cu km. Another even larger recent flow from Giant Crater on the south flank produced a lava flow that traveled 45 km to the south, well beyond the flanks of the volcano, about 10,600 years ago.

Photo by Peter Lipman, 1981 (U.S. Geological Survey).
Medicine Lake volcano, seen here from the east with Mount Shasta in the background, is a massive, low shield volcano truncated by a 7 x 12 km summit caldera that is partially filled by Medicine Lake on the left. The barren Medicine dacite flow on the right was erupted about 2000 years ago. During the Holocene, obsidian flows have been erupted from summit and flank vents and voluminous basaltic lava flows have erupted from vents on the north and south flanks.

Photo by Dan Dzurisin, 1985 (U.S. Geological Survey).
A vertical aerial photo shows the lobate form of the Glass Mountain obsidian flow, erupted less than 1000 years ago from a series of vents near the buried east rim of Medicine Lake caldera. The Glass Mountain eruption originated from a series of NW-SE-trending vents, seen here cutting across the photo from the upper left. Initial dacitic lavas were transitional into rhyolitic obsidian flows. The smoother-textured, partially vegetated lava flow at the lower left is the dacitic Hoffman flow, erupted only a few hundred years prior to the Glass Mountain flow.

Photo by U.S. Geological Survey (published in Green and Short, 1971).
The andesitic Burnt Lava flow covering about 37 sq km of the SE flank of Medicine Lake volcano was erupted from the High Hole Crater cinder cone. The Burnt Lava flow was the largest from Medicine Lake during the Holocene and had a volume of 0.45 cu km. The symmetrical High Hole Crater contains a double summit crater. The Burnt Lava flow, which was erupted from both High Hole Crater and adjacent fissures, surrounded two older cinder cones, one of which forms the forested ridge at the left.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
The most voluminous Holocene lava flow on the southern flank of Medicine Lake volcano is known as the Burnt Lava flow. The flow, which originated from High Hole Crater and nearby fissure vents, covers 37 sq km. The flow is dominantly aa lava, but also includes some pahoehoe. This photo shows the NW margin of the flow, which was erupted about 2750 years ago.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
The broad 50-km-wide Medicine Lake volcano in the southern Cascade Range of NE California, seen here from the NE, is an example of a large shield volcano in a continental margin setting. Its chemistry is more diverse than Hawaiian shield volcanoes, and it has produced both basaltic lava flows and rhyolitic tephras and obsidian flows during the Holocene. Eruptions have occurred during the past 6000 years from vents within a 7 x 11 km summit caldera and from other vents on its flanks.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
Despite its youthful appearance, the Devils Homestead lava flow in the foreground is slightly more than 10,000 years old. Erosional modification of lava flow surfaces proceeds slowly in arid regions. The Devils Homestead flow is one of the largest on the north flank of Medicine Lake volcano, the broad shield volcano on the horizon. Flank cinder cones dot the slopes of the chemically diverse shield volcano, which has produced both the basaltic cinder cones and lava flows seen here, and dacitic and rhyolitic pumice and lava flows.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
Lava Beds National Monument contains nearly 300 lava-tube caves associated with fluid basaltic lava flows on the flanks of Medicine Lake volcano in northern California. The sides of this large lava tube, known as Valentine Cave, show the pronounced "bathtub rings" left by lava flowing through the tube. Valentine Cave is an example of a lava tube from which lava almost completely drained. The Valentine lava flow was erupted about 10,850 radiocarbon years ago, and is one of the largest flows on the northern flank of Medicine Lake caldera.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
Minor amounts of basaltic lava were erupted about 3000 years ago from spatter cones at Black Crater and Ross Chimneys on the lower northern flank of Medicine Lake volcano. The spatter cone in the foreground was the vent for the sparsely vegetated small overlapping pahoehoe lava flows in the middle part of the photo. The dark lava flow in the distance in front of a fault block of older lavas, is the late-Pleistocene Devils Homestead lava flow.

Photo by Lee Siebert, 1988 (Smithsonian Institution).
Medicine Lake, a popular camping and recreation destination in northern California, is a small 2-km-long lake that occupies the SW side of Medicine Lake caldera. The forested southern rim of the 7 x 11 km caldera forms the horizon. Medicine Lake volcano is known for its young obsidian flows within the caldera and on its flanks.

Photo by Lee Siebert, 1988 (Smithsonian Institution).
Cinder Butte (upper left) on the north side of massive Medicine Lake volcano was the source of a voluminous lava flow that is the most recent on the volcano's north flank. The cone is seen here from the east from the rim of Mammoth Crater in Lava Beds National Monument. Cinder Butte was formed during an eruption about 800 AD that also produced the sparsely vegetated Callahan lava flow, which can be seen extending down the north flank to the right.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
The basaltic Callahan lava flow, erupted from the Cinder Butte cone, is the largest Holocene lava flow on the north flank of Medicine Lake volcano. The broad Callahan flow is seen here from the reddish oxidized rim of Cinder Butte diverging around an older cinder cone to the north. The flow was dated from radiometric and paleomagnetic evidence at about 800 AD. The Callahan flow is chemically zone, with initial lavas being andesitic and later lavas basaltic.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
The Glass Mountain obsidian flow, seen here from Lyons Peak on the east rim of Medicine Lake caldera, was erupted from a series of vents just outside the buried inferred eastern rim of the caldera. The youthful, steep-sided rhyolitic and dacitic flow is both the largest and youngest of a series of Holocene rhyolitic and dacitic flows at Medicine Lake. The 1 cu km flow was erupted about 900 years ago. The flow traveled a short distance west (left) into the caldera, but mostly flowed down the eastern flank, reaching a point about 6 km from its source.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
The Glass Mountain obsidian flow buries much of the eastern rim of Medicine Lake caldera. The massive 1 cu km flow traveled south towards Lyons Peak (upper right) before the bulk of the flow was diverted to the east and descended the caldera's outer flank. The latest event at Glass Mountain produced the craggy rhyolitic obsidian dome seen in the foreground. The roughly 900-year-old flow is the youngest and largest of a series of Holocene rhyolitic and dacitic lava flows at Medicine Lake.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
Blocks of glassy obsidian reflect sunlight from the surface of a rhyolitic lava dome marking the latest eruptive event during extrusion of the Glass Mountain lava flow. The composite flow originated from more than a dozen NW-SE-trending vents near the eastern rim of the Medicine Lake caldera. Part of the massive obsidian flow seen on the left side of the photo traveled west into the caldera. Snow-capped Mount Shasta towers above the forested caldera rim to the west.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
The broad partially forested lava flow extending across the center of the photo into Medicine Lake caldera is the Hoffman lava flow, erupted about 1230 years ago. The massive rhyolitic lava flow and an adjacent smaller one were erupted from six or more vents on the NE rim of the caldera. The larger of the two flows, seen here with the unvegetated Glass Mountain flow in the foreground, was erupted near the caldera rim and flowed both west into the caldera and down the east flank. Snow-capped Mount Shasta rises to the west.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
The western terminous of the dacitic Hoffman lava flow forms a steep-sided blocky cliff ranging up to about 50 m in height. The Hoffman flow and a rhyolite flow on the NE side of Mt. Hoffman were erupted about 1230 years ago. The flows originated from six or more NW-SE-trending vents, and were preceded by eruption of tephra. The larger of the two flows (seen here) was erupted near the eastern caldera rim and flowed primarily west into the caldera, although a smaller portion traveled to the east.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
The Medicine Lake lava flow, seen here from the NW with Medicine Lake in the background, was erupted onto the caldera floor from an inconspicuous vent near the north caldera rim. Unlike other large rhyolitic lava flows at Medicine Lake, it apparently was not preceded by a major explosive eruption. The flat-lying, viscous 0.08 cu km lava flow is not precisely dated, but is known from stratigraphic evidence to have been emplaced sometime between the roughly 780 BC Burnt Lava flow and the roughly 720 AD Hoffman flow.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
This pit crater on the SE rim of Medicine Lake caldera was formed during the first Holocene eruption of the volcano, about 4350 years ago. The eruption, which followed a quiescent period of about 6000 years, produced andesitic scoria from a NE-trending alignment of pit craters. Agglutinated spatter formed small lava flows.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
The Little Glass Mountain obsidian flow is seen here from Pumice Stone Mountain, named for the mantle of white pumice (foreground) from Little Glass Mountain that mantles the cone. The massive 0.4 cu km obsidian flow was erupted from a buried vent below Little Mt. Hoffman, which rises above the skyline at right center on the western rim of Medicine Lake caldera. The Little Glass Mountain pumice eruption and obsidian flow occurred about 1065 years ago during one of the youngest eruptions from Medicine Lake.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
The steep-sided SW margin of the Little Glass Mountain obsidian flow rises above the surrounding forested flanks of Medicine Lake volcano. Eruption of the rhyolitic lava flow was preceded by a pumice eruption that mantled the surrounding area (including the basaltic cone of Pumice Stone Mountain in the foreground) with white pumice. The 0.4 cu km Little Glass Mountain lava flow is the second largest silicic lava flow at Medicine Lake.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
The back side of light-colored Paint Pot Crater and Pumice Stone Mountain, from where the photo was taken, are mantled by white pumice from the eruption that preceded the extrusion of the nearby Little Glass Mountain obsidian flow. The formation of Paint Pot Crater and the associated extrusion of the lava flow that forms the sparsely vegetated area south (right) of the cone occurred about 1100-1150 years ago, only shortly before the major Little Glass Mountain eruption.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
Paint Pot Crater on the lower SW flank of Medicine Lake volcano derives its name from the mantle of white pumice from nearby Little Glass Mountain that covers the reddish oxidized scoria of the cinder cone. Paint Pot Crater emitted a lava flow from its breached crater that traveled to the south, where it forms the sparsely vegetated area seen in the photo beyond the far rim of the cone. The crater and lava flow are among the youngest products of Medicine Lake volcano, and were erupted about 1100-1150 years ago.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
The broad Medicine Lake shield volcano, seen here on the horizon from Soldier Mountain to its south, is truncated by a 7 x 11 km caldera. Medicine Lake volcano has erupted lavas of widely varying composition ranging from basalt to rhyolite. The largest eruption of Medicine Lake during the past 11,000 years produced a massive basaltic lava flow from Giant Crater about 10,600 years ago. The flow traveled a distance of 45 km down the broad valley in the center of the photo from its vent on the SSW flank.

Photo by Lee Siebert, 1998 (Smithsonian Institution).

The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title.

Anderson C A, 1941. Volcanoes of the Medicine Lake Highland California. Univ Calif Pub Geol Sci, 25: 347-422.

Coombs H A, Howard A D, 1960. United States of America. Catalog of Active Volcanoes of the World and Solfatara Fields, Rome: IAVCEI, 9: 1-68.

Donnelly-Nolan J M, Champion D E, 1987. Geologic map of Lava Beds National Monument, northern California. U S Geol Surv Map, I-1804.

Donnelly-Nolan J M, Champion D E, Miller C D, Grove T L, Trimble D A, 1990. Post-11,000-year volcanism at Medicine Lake volcano, Cascade Range, northern California. J Geophys Res, 95: 19,693-19,704.

Donnelly-Nolan J M, Champion D E, Miller C D, Trimble D A, 1989. Implications of post-11,000-year volcanism at Medicine Lake volcano, northern California Cascade Range. In: Muffler L J P and Weaver C S (eds) {Geology, Geophysics and Tectonic Setting of the Cascade Range}, U S Geol Surv, Open-File Rpt 89-178: 556-580.

Donnelly-Nolan J M, Grove T L, Lanphere M A, Champion D E, Ramsey D W, 2008. Eruptive history and tectonic setting of Medicine Lake volcano, a large rear-arc volcano in the southern Cascades. J Volc Geotherm Res, 177: 313-328.

Donnelly-Nolan J M, Nathenson M, Champion D E, Ramsey D W, Lowenstern J B, Ewert J W, 2007. Volcano hazards assessment for Medicine Lake volcano, northern California. U S Geol Surv Sci Invest Rpt, 2007-5174-A: 1-26.

Fink J H, 1983. Structure and emplacement of a rhyolite obsidian flow: Little Glass Mountain, Medicine Lake Highland, northern California. Geol Soc Amer Bull, 94: 362-380.

Heiken G, 1978a. Characteristics of tephra from Cinder Cone, Lassen Volcanic National Park, California. Bull Volc, 41: 119-130.

Kilbourne R T, 1982. Chronology of eruptions in California during the last 2,000 years. Calif Dept Conservation Div Mines Geol Spec Pub, 63: 29-40.

Macdonald G A, 1966. Geology of the Cascade Range and Modoc Plateau. Calif Div Mines Geol Bull, 190: 65-95.

Mertz S A Jr, 1977. Recent volcanism at Schonchin and Cinder Buttes, northern California. Contr Mineral Petr, 61: 231-243.

Waters A C, Donnelly-Nolan J M, Rogers B W, 1990. Selected caves and lava-tube systems in and near Lava Beds National Monument, California. U S Geol Surv Bull, 1673: 1-102 and 6 plates.

Volcano Types

Shield
Caldera
Cinder cone(s)
Lava dome(s)

Tectonic Setting

Subduction zone
Continental crust (> 25 km)

Rock Types

Major
Basalt / Picro-Basalt
Andesite / Basaltic Andesite
Rhyolite
Minor
Dacite

Population

Within 5 km
Within 10 km
Within 30 km
Within 100 km
0
0
254
120,685

Affiliated Databases

Large Eruptions of Medicine Lake Information about large Quaternary eruptions (VEI >= 4) is cataloged in the Large Magnitude Explosive Volcanic Eruptions (LaMEVE) database of the Volcano Global Risk Identification and Analysis Project (VOGRIPA).
WOVOdat WOVOdat is a database of volcanic unrest; instrumentally and visually recorded changes in seismicity, ground deformation, gas emission, and other parameters from their normal baselines. It is sponsored by the World Organization of Volcano Observatories (WOVO) and presently hosted at the Earth Observatory of Singapore.
EarthChem EarthChem develops and maintains databases, software, and services that support the preservation, discovery, access and analysis of geochemical data, and facilitate their integration with the broad array of other available earth science parameters. EarthChem is operated by a joint team of disciplinary scientists, data scientists, data managers and information technology developers who are part of the NSF-funded data facility Integrated Earth Data Applications (IEDA). IEDA is a collaborative effort of EarthChem and the Marine Geoscience Data System (MGDS).
Smithsonian Collections Search the Smithsonian's NMNH Department of Mineral Sciences collections database. Go to the "Search Rocks and Ores" tab and use the Volcano Name drop-down to find samples.