USGS/Cascades Volcano Observatory, Vancouver, Washington
DESCRIPTION:
Mount Mazama Volcano and Crater Lake Caldera, Oregon
- Crater Lake Caldera and Mount Mazama Volcano
- Geographic Setting
- Geologic Setting
- Crater Lake History
- Mount Mazama
- Pre-Climactic Eruption - Mount Mazama
- The Climactic Eruption - Formation of Crater Lake Caldera
- Mazama Ash
- Post-Climactic Eruption Activity - Wizard Island and Merriam Cone
- Hydrothermal Activity
- Volcano and Hydrologic Monitoring
- Crater Lake National Park
- Crater Lake National Park - Points of Interest
- Chaski Bay Landslide
- Cleetwood Flow
- Crater Lake
- Discovery Point
- Grouse Hill
- Hillman Peak
- Llao Rock
- Merriam Cone
- Mount Scott
- Palisades Point
- Phantom Ship
- Redcloud Flow
- Wizard Island
Crater Lake Caldera and Mount Mazama Volcano
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CraterLake05_aerial_crater_lake_mount_scott_12-10-05.jpg
Aerial view, Crater Lake, Wizard Island, and Mount Scott, as seen from the west.
USGS Photograph taken on December 10, 2005, by Mike Doukas.
[medium size] ...
[large size]
Compiled From:
1
Smithsonian Institution - Global Volcanism Program Website, 1998,
2
Wright and Pierson, 1992,
Living With Volcanoes, The U.S. Geological Survey's Volcano Hazards Program:
USGS Circular 1073,
and
3
Foxworthy and Hill, 1982,
Volcanic Eruptions of 1980 at Mount St. Helens, The First 100 Days:
USGS Professional Paper 1249
- Crater Lake Caldera
- Location: Oregon
- Latitude: 42.93 N
- Longitude: 122.12 W
- Height: 2,487 meters (8,156 feet - Hillman Peak)
- Type:
Caldera
- Number of eruptions in the past 200 years:
0
- Latest Eruptions:
4,000 years ago 2 ...
at least 800-900 years ago (Wizard Island) 3.
- Present thermal activity:
None
- Remarks:
Largest known eruption from Cascade Range volcano. Catastrophic,
caldera-forming eruption 7,000 years ago; post-caldera lava and domes
2 ...
From a probable altitude of roughly 12,000 feet, the top of former Mount Mazama
was lost to eruption and collapse that left the present huge crater and the
deepest lake (1,932 feet) in North America. Explosive eruptions
built Wizard Island
and two other cones (submerged) on present
crater floor 3.
From:
Wood and Kienle, 1990, Volcanoes of North America: United States and Canada:
Cambridge University Press, 354p., p.193-195,
Contribution by Charles R. Bacon
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Crater Lake
caldera
formed by collapse during the
catastrophic eruption
of approximately 50 cubic
kilometers of magma, 6,845 carbon-14 years B.P. (before present). The 8x10
kilometer caldera lies in the remains of Mount Mazama, a
Pleistocene
stratovolcano cluster
covering 400 square kilometers in the southern Oregon Cascades. Prior to its
climactic eruption, Mount Mazama's summit had an elevation between 3,300 meters
and 3,700 meters (10,800 - 12,000 feet).
Its southern and southeastern flanks were deeply incised by
glacial valleys, now beheaded, that form U-shaped notches in the caldera wall.
-
Mazama was one of the major volcanoes of the
High Cascades
and is the largest edifice between
Mount Shasta and the
Three Sisters
volcanoes. Around Mazama are monogenetic
cinder cones,
lava fields, and small
shield volcanoes
that produced calc-alkaline basalt and andesite, primitive tholeiite, and rare
shoshonitic andesite. These range in age from around 600,000 years to perhaps
40,000 years ago, and are similar to monogenetic volcanoes up and down the High
Cascades.
-
Individual stratovolcanoes and shields that make up Mount Mazama
become younger
in a west-northwest sense.
The oldest Mazama lavas dated are flows near lake
level at
Phantom Ship
and the lavas of
Mount Scott (around 400,000 years). The youngest
stratovolcano is Hillman Peak (around 70,000 years). Local andesite
flows on the north rim are 50-40,000 years old.
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Post-caldera volcanic landforms are present beneath the lake surface and poke
through to form Wizard Island.
The central platform, Merriam Cone, and Wizard Island are all andesite evidently
erupted within a few hundred years of caldera collapse. The small rhyodacite dome
30 meters belows lake level one kilometer east of Wizard Island is the
youngest feature. ...
From:
U.S. National Park Service, Crater Lake National Park Website, 2001
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Crater Lake is located in Southern Oregon on the crest of the
Cascade Mountain range, 100 miles (160 kilometers) east of the
Pacific Ocean. It lies inside a
caldera, or volcanic basin,
created when the 12,000 foot (3,660 meter) high
Mount Mazama collapsed 7,700 years ago following a large eruption.
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Generous amounts of winter snow, averaging 533 inches
(1,354 centimeters) per year, supply the lake with water. There are no
inlets or outlets to the lake. Crater Lake, at 1,958 feet (597
meters) deep, is the seventh deepest lake in the world and the
deepest in the United States. Evaporation and seepage
prevent the lake from becoming any deeper.
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The lake averages more than five miles (8 kilometers) in diameter,
and is surrounded by steep rock walls that rise up to 2,000 feet
(600 meters) above the lake's surface.
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Following the collapse of Mount Mazama, lava poured into the
caldera even as the lake began to rise. Today, a small volcanic
island, Wizard Island, appears on the west side of the lake.
This
cinder cone
rises 760 feet (233 meters) above the lake
and is surrounded by black volcanic lava blocks. A small crater,
300 feet (90 meters) across and 90 feet (27 meters) deep,
rests on the summit. The crater is filled by snow during the
winter months, but remains dry during the summer.
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The lake level fluctuates slightly from year to year. The highest
level was reached in 1975 when the water level rose to
6,179.34 feet (1,883.47 meters) above sea level. The lowest
level was recorded in 1942 when it dropped to 6,163.20 feet
(1,878.55 meters). For such a deep lake, the maximum
observed variation of 16 feet (5 meters) is minor (less than 1
percent).
From:
Bacon, Mastin, Scott, and Nathenson, 1997,
Volcano and Earthquake Hazards in the Crater Lake Region, Oregon:
USGS Open-File Report 97-487
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Mount Mazama and Crater Lake caldera lie at
the intersection of the Cascade chain of volcanoes with
the Klamath graben, a north-northwest trending basin
bounded by faults whose displacement is mainly vertical.
At this latitude, the western margin of the
Basin and Range province, characterized by north-south
to northwest-southeast trending faults, impinges upon
the Cascades. Focusing of volcanism at Crater Lake
and the development of the shallow magma chamber
which fed the climactic eruption are linked to this
regional tectonic situation.
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North and south of Crater Lake are many shield
volcanoes of modest size and many more cinder
cones with associated lava flow fields. Both represent
short-lived activity at isolated vents. These
monogenetic volcanoes are manifestations of
regional volcanism throughout the Oregon Cascades.
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Mount Mazama is the name applied to the
volcano in which Crater Lake caldera formed.
Before the caldera-forming eruption, the summit of
Mount Mazama stood at ~3,700 meters (~12,000 feet)
elevation. Mount Mazama was constructed during the
last approximately 400,000 years by episodic growth
of many overlapping shield and composite volcanoes,
each of which probably was active for a comparatively
brief period (Bacon, 1983). The erupted magma was
mainly andesite. As the volcanic complex evolved, so
did its eruptive style, such that the last ~70,000 years
saw more highly explosive eruptions of silicic magma
(dacite and rhyodacite). In the last ~30,000 years,
the only record of activity, prior to the caldera-forming
climactic eruption of ~7,700 years ago, was limited to
a small number of preclimactic pyroclastic eruptions
and ensuing lava flows of rhyodacite. Subsequent to
the climactic eruption, all volcanic activity has occurred
within the caldera itself. Wizard Island is a cinder cone
and lava flows of postcaldera andesite, erupted soon
after the caldera formed. Several more postcaldera
volcanoes are hidden by the lake.
From:
Bacon, Mastin, Scott, and Nathenson, 1997,
Volcano and Earthquake Hazards in the Crater Lake Region, Oregon:
USGS Open-File Report 97-487
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[Map,38K,InlineGIF]
Generalized Geologic Map of Mount Mazama and Vicinity
-- Modified from: Bacon, et.al., 1997,
USGS Open-File Report 97-487
Excerpts from:
U.S. National Park Service Website, Crater Lake National Park, June 2001
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Local Native Americans witnessed the collapse of Mount Mazama and kept the event
alive in their legends. One ancient legend of the Klamath people closely parallels the
geologic story which emerges from today's scientific research. The legend tells of two
Chiefs, Llao of the Below World and Skell of the Above World, pitted in a battle which
ended up in the destruction of Llao's home, Mt. Mazama. The battle was witnessed in
the eruption of Mt. Mazama and the creation of Crater Lake.
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In the spring of 1853, eleven miners from Yreka, California stopped in for
supplies at Isaac Skeeter's mercantile store in Jacksonville, Oregon
(approximately 90 miles south of Crater Lake). They began bragging that they
knew how to find the legendary "Lost Cabin" gold mine. Skeeters quickly
gathered up ten other Oregonians and set out, using the information overheard
in his store. The trip was financed by John Wesley Hillman, a 21 year old who
had recently returned home from a successful trip to the California goldfields.
On June 12, three members from this party came upon a large body of water
sitting in a huge depression. Hillman exclaimed that it was the bluest water he
had ever seen. Skeeters suggested the name "Deep Blue Lake." Lack of
provisions soon drove the miners down the mountains and back to Jacksonville
where they reported the discovery of the lake. However, without the prospects
of gold and fear of the unknown region to the north, there was no interest in
confirming this discovery. It was soon forgotten.
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In 1862, another party of Oregon prospectors explored this area of the Cascade Range, including Crater
Lake. The leader, Chauncy Nye, subsequently wrote a short article for the Jacksonville Oregon Sentinel.
His article stated, "The waters were of a deeply blue color causing us to name it Blue Lake". This piece is
the first published description of the lake.
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Hostilities between settlers and Native Americans developed in the area. In response, the U.S. Army
established Fort Klamath seven miles southeast of the present park boundary in 1863. This led to the
construction of a wagon road from Prospect in the Rogue River Valley to the newly established Fort
Klamath. On August 1, 1865, the lake was "rediscovered" by two hunters attached to the road crews.
Several soldiers and civilians journeyed to see the now-legendary lake. One of the participants, Sergeant
Orsen Stearns, was so awestruck by what he saw that he climbed down into the caldera and became the
first non- Native American to reach the shore of Crater Lake. Captain F. B. Sprague soon joined him and
suggested the name "Lake Majesty."
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In July, 1869, newspaper editor Jim Sutton and several others decided to visit Lake Majesty and explore it
by boat. By August, a canvas boat had been constructed and lowered onto the lake. Five people reached
Wizard Island and spent several hours exploring the cinder cone. Sutton wrote an article describing the trip
for his Jacksonville newspaper. Instead of Lake Majesty, Sutton substituted the name "Crater Lake" for the
crater on top of Wizard Island.
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William Gladstone Steel devoted his life and fortune to the establishment and
management of Crater Lake National Park. His preoccupation with the lake began in
1870. In his efforts to bring recognition to the park, he participated in lake surveys that
provided scientific support. He named many of the lake's landmarks, including Wizard
Island, Llao Rock, and Skell Head. Steel's dream was realized on May 22, 1902 when
President Theodore Roosevelt signed the bill giving Crater Lake national park status.
And because of Steel's involvement, Crater Lake Lodge was opened in 1915 and the
Rim Drive was completed in 1918.
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In 1886, Steel assisted with the mapping of the lake, which had been undertaken by Clarence Dutton for the
U.S. Geological Survey. During the original survey, soundings of the lake were conducted using pipe and
piano wire. The maximum depth determined by the survey was 1,996 feet {608 meters), only 64 feet off
from the sonar measurement of 1,932 feet officially recorded in 1959.
From:
Klimasauskas, et.al., 2002
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Mount Mazama was formed over a period of nearly half a
million years by a succession of overlapping
volcanoes. The first eruptions about 420,000 years
ago built Mount Scott, located just east of Crater Lake. Over
the next several hundred thousand years,
Mount Scott and other nearby volcanoes became extinct, while new
volcanoes grew to the west. Layers of lava flows from
these volcanoes are visible in the caldera walls and in
landmarks along the south rim of Crater Lake,
including Applegate and Garfield Peaks. During the growth of
Mount Mazama, glaciers repeatedly carved out
classic U-shaped valleys. Some were filled with lava from later
eruptions, while others, such as Kerr Notch and Sun Notch, were not.
By about 30,000 years ago, Mount Mazama began to
generate increasingly explosive eruptions that were
followed by thick flows of silica-rich lava,
an outward sign of the slow accumulation of a large volume of highly
explosive magma deep beneath the volcano.
Grouse Hill and Redcloud Cliff are thick lava flows erupted
between 30,000 and 25,000 years ago.
Another such eruption about 7,900 years ago formed a white layer of
pumice and ash and the thick lava flow of Llao Rock.
Within 200 years of the eruption at Llao Rock, another
thick lava flow erupted near present-day Cleetwood Cove.
These eruptions reached a peak 7,700 years ago in
the largest explosive eruption in the Cascades during the past 1 million years.
From:
Bacon, Mastin, Scott, and Nathenson, 1997,
Volcano and Earthquake Hazards in the Crater Lake Region, Oregon:
USGS Open-File Report 97-487
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Mount Mazama is the name applied to the
volcano in which Crater Lake caldera formed.
Before the caldera-forming eruption, the summit of
Mount Mazama stood at ~3,700 meters (~12,000 feet)
elevation. Mount Mazama was constructed during the
last approximately 400,000 years by episodic growth
of many overlapping shield and composite volcanoes,
each of which probably was active for a comparatively
brief period (Bacon, 1983). The erupted magma was
mainly andesite. As the volcanic complex evolved, so
did its eruptive style, such that the last ~70,000 years
saw more highly explosive eruptions of silicic magma
(dacite and rhyodacite). In the last ~30,000 years,
the only record of activity, prior to the caldera-forming
climactic eruption of ~7,700 years ago, was limited to
a small number of preclimactic pyroclastic eruptions
and ensuing lava flows of rhyodacite. Subsequent to
the climactic eruption, all volcanic activity has occurred
within the caldera itself. Wizard Island is a cinder cone
and lava flows of postcaldera andesite, erupted soon
after the caldera formed. Several more postcaldera
volcanoes are hidden by the lake.
From:
Mazamas FAQ, Mazamas Website, 2002
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From the unabridged Webster's dictionary:
From mazame (see mazama) from Nahuatl "mazatl" (deer)
"A name applied by early writers to various
American ruminants supposed to be the Rocky Mountain Goat."
The club founders thought that the strongest climber in the mountains
(the goat) was an appropriate symbol. The southern Oregon
mountain that collapsed and became Crater Lake (Mt. Mazama)
was named for the club.
Pre-Climactic Eruption - Mount Mazama
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From:
Wood and Kienle, 1990, Volcanoes of North America: United States and Canada:
Cambridge University Press, 354p., p.193-195,
Contribution by Charles R. Bacon
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Crater Lake
caldera
formed by collapse during the
catastrophic eruption
of approximately 50 cubic
kilometers of magma, 6,845 carbon-14 years B.P. (before present). The 8x10
kilometer caldera lies in the remains of Mount Mazama, a
Pleistocene
stratovolcano cluster
covering 400 square kilometers in the southern Oregon Cascades. Prior to its
climactic eruption, Mount Mazama's summit had an elevation between 3,300 meters
and 3,700 meters (10,800 - 12,000 feet).
Its southern and southeastern flanks were deeply incised by
glacial valleys, now beheaded, that form U-shaped notches in the caldera wall.
-
Mazama was one of the major volcanoes of the
High Cascades
and is the largest edifice between Mount Shasta and the Three
Sisters volcanoes. Around Mazama are monogenetic
cinder cones,
lava fields, and small
shield volcanoes
that produced calc-alkaline basalt and andesite, primitive tholeiite, and rare
shoshonitic andesite. These range in age from around 600,000 years to perhaps
40,000 years ago, and are similar to monogenetic volcanoes up and down the High
Cascades.
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Beneath the eastern half of Mount Mazama and extending to the southeast
is an extensive field of rhyodacite flows and doms, apparently 700-600,000 years
old, covering at least 350 square kilometers. Hornblende dacite underlies the
rhyodacite in the southeastern part of the field. Generally north-south
trending normal faults cut monogenetic vent lavas and rhyodacite, with most
displacement down to the east. The same faults cut older Mazama flows, but
dispalcements are not evident in the younger lavas and no tectonic faults have
been detected in the caldera walls.
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Individual stratovolcanoes and shields that make up Mount Mazama
become younger
in a west-northwest sense. The oldest Mazama lavas dated are flows near lake
level at Phantom Ship
and the lavas of Mount Scott (around 400,000 years). The youngest
stratovolcano is Hillman Peak (around 70,000 years). Local andesite
flows on the north rim are 50-40,000 years old.
Shields are composed of sheet
flows of agglutinated mafic andesite that are typically around 5 meters thick
and form bands on the caldera walls. More viscous magma of andesite and dacite
flows resulted in thicker flow units, up to 30 meters with larger proportions of
flow-top rubble to dense lava. Even so, most of these also appear to be
composed of agglutinated bombs. Undercooled inclusions of crystal-poor andesite
magma are common in many andesite and dacite flows. Such flows make up Mount
Scott (2,271 meters), east of the caldera rim, and Phantom Cone and
other centers evident in the southern caldera walls. Some andesite lava flowed
into glacial valleys forming thick intracanyon flows, such as at Sentinel
Rock. At many places in the caldera walls and on the flanks of Mazama
exposures of small glassy columns and piles of monolithologic glassy breccia
provide evidence of lava/ice interaction. Many flows bury glaciated lava
surfaces.
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Explosive silicic eruptions occurred at several vents around 70,000 years ago.
The most impressive was at Pumice Castle on the east wall, where layers
of a dacitic Plinian fall deposit become densely welded near their vent. The
deposit is non-welded to the south and in poor exposures on the north caldera
wall from Cleetwood Cove to Steel Bay. Other welded dacite pumice
fall deposits occur on the north side of Cloudcap and in the wall beneath
the east flank of Llao Rock. Dacite pyroclastic flow deposits are
present below Llao Rock and in the southwest wall. The Watchman
flow is also dacite, as are monolithologic breccias and
lithic-pyroclastic-flow deposits in the had of Munson Valley. Dacite
forms the silicic endmember in the basalt-andesite-dacite mingled lavas of
William Crater (formerly Forgotten Crater). There is no evidence
of andesitic or dacitic volcanism between 40,000 years ago and the climactic
eruption.
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Rhyodacitic magma erupted as pumice and lava flows between 30 and 25,000 years
ago at Grouse Hill, Steel Bay, and Redcloud Cliff. All are
hornblende phyric, chemically evolved rhyodacite that apparently leaked from the
growing climactic magma chamber, Sharp Peak and adjacent rhyodacite domes
form a northeast-trending linear array that probably vented in the latest
Pleistocene or early Holocene. They are compositionally identical with
climactic rhyodacite (70% SiO2). The Llao Rock flow and preceding
Plinian fall deposit were erupted 7,015 years ago and are zoned from 72 to 70
percent SiO2. The Cleetwood flow and pumice were erupted 100-200 years
later, because the flow was still hot when the caldera collapsed during the
climactic eruption at 6,845 years B.P. Cleetwood and climactic
rhyodacites are compositionally homogeneous and identical. This rhyodacite
makes up around 90 percent of the volume of climactic ejecta.
The Climactic Eruption -
Formation of Crater Lake Caldera
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From:
Tilling, 1985,
Volcanoes: USGS General Interest Publication
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An interesting variation of a
composite volcano
can be seen at Crater Lake
in Oregon. From what geologists can interpret of its past, a high volcano --
called Mount Mazama -- probably similar in appearance to
present-day Mount Rainier was once located at this spot.
Following a series of tremendous
explosions about 6,600 years ago, the volcano lost its top. Enormous volumes of
volcanic ash and dust were expelled and swept down the slopes as ash flows and
avalanches. These large-volume explosions rapidly drained the lava beneath the
mountain and weakened the upper part. The top then collapsed to form a
large depression,
which later filled with water and is now completely occupied by
beautiful Crater Lake. A last gasp of eruptions produced a small
cinder cone
which rises above the water surface as Wizard Island in, and near the rim, of the lake.
From:
Wood and Kienle, 1990, Volcanoes of North America: United States and Canada:
Cambridge University Press, 354p., p.193-195,
Contribution by Charles R. Bacon
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Crater Lake
caldera
formed by collapse during the catastrophic eruption of approximately 50 cubic
kilometers of magma, 6,845 carbon-14 years B.P. (before present). The 8x10
kilometer caldera lies in the remains of Mount Mazama, a
Pleistocene
stratovolcano cluster
covering 400 square kilometers in the southern Oregon Cascades. Prior to its
climactic eruption, Mount Mazama's summit had an elevation between 3,300 meters
and 3,700 meters. ...
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The climactic eruption began as a
plinian column
producing a widespread fall deposit mainly to the north-northeast. This column
eventually collapsed and generated at least four flow units which colled
together to form the Wineglass Welded Tuff. The Wineglass
is present
only on the north and east flanks of Mazama, and thus the vent for this
valley-hugging ignimbrite was north of the summit. Eruption of the
Wineglass
ceased with onset of caldera collapse when highly mobile pyroclastic flows,
derived from many vents, traveled radially down the flanks of the mountain to
fill all the major drainages. Near the caldera and on all high ground these
ring-vent-phase deposits consist of lithic breccia, while pumiceous ignimbrite
occupies the valleys.
This deposit is spectacularly compositionally zones: homogeneous rhyodacite (70%
SiO2) followed by andesite (<61% SiO2) and mafic cumulate scoria (to as low
as around 48% SiO2). ...
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Timing of caldera collapse is well documented, because the interior of the
Cleetwood flow was sufficiently plastic at the time of the climactic
eruption that remobilizsed lava flowed northeast in response to seismicity and
also down the caldera wall at Cleetwood Cove. Scarps on the brittle flow
surface expose Plinian fall deposit and thin Wineglass Welded Tuff, but
the proximal lithic breccia of the ring-vent-phase ignimbrite is banked agains
them, indicating disruption of the Cleetwood flow surface after
emplacement and welding of less than 2 meters of Wineglass but beofre deposition
of the last lithic breccia. Thick, densely welded Wineglass in paleovalleys at
the caldera rim sagged towards the caldera, showing that collapse took place
before complete solidification fo this ignimbrite.
From:
Hoblitt, Miller, and Scott, 1987,
Volcanic Hazards with Regard to Siting Nuclear-Power Plants
in the Pacific Northwest:
USGS Open-File Report 87-297
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Crater Lake occupies a
caldera
formed 6,850 years ago during the climactic eruption of Mount Mazama
which was a cluster of
Pleistocene
stratovolcanoes.
A period of 15,000-40,000 years was required to form the silicic component
of the climactic magma chamber.
During that period, eruptions of basalt, andesite, dacite, and rhyolite
occurred in the Mount Mazama area.
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During the few centuries preceding the climactic eruption,
at least two small- to moderate-volume
(<1 to several cubic kilometers) eruptions of rhyolite occurred
in the area underlain by the magma chamber.
Tephra from one of these eruptions
extended into southeastern Oregon and western Nevada and
the same tephra, or one or more others, fell as far away as eastern Washington.
The explosive eruptions were followed by the extrusion of rhyolite lava flows.
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The climactic eruptions 6,850 years ago produced
voluminous tephra-fall
and pyroclastic-flow deposits.
The tephra deposits are about 40 centimeters thick at points 200 kilometers
northeast of the volcano and 4-5 centimeters thick at 1000 kilometers;
layers have been found in 8 western states
and 3 Canadian provinces.
The tephra fall was followed by two episodes of pyroclastic-flow formation.
The first was of small extent, but it was followed by voluminous
pyroclastic flows that moved outward in
all directions to distances of as much as 60 kilometers.
The total volume of magma
erupted during the climactic eruption was about 50-60 cubic kilometers,
which is an order of magnitude
larger than that produced during any other explosive
eruption in the Cascade Range during postglacial time.
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Following the climactic eruption, an andesite scoria cone and
lava flows were erupted within the
caldera to form Wizard Island.
The initial postcaldera eruptions probably occurred shortly
after the climactic eruption, prior to the
development of the lake. Other eruptions occurred after
the lake had begun to form. A
rhyolite dome
on the flank of the Wizard Island volcano records the
youngest known eruptive activity.
From:
Bacon, 1983,
Eruptive History of Mount Mazama and Crater Lake Caldera, Cascade Range, U.S.A.:
Journal of Volcanology and Geothermal Research, v.18, p.57-115
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New investigations of the geology of
Crater Lake National Park
necessitate a
reinterpretation of the eruptive history of Mount Mazama
and of the formation of
Crater Lake caldera. Mount Mazama consisted of a glaciated complex of
overlapping shields and stratovolcanoes, each of which was probably active for a
comparatively short interval. All the Mazama magmas apparently evolved within
thermally and compositionally zoned crustal magma reservoirs, which reached
their maximum volume and degree of differentiation in the climactic magma
chamber approximately 7,000 years B.P.
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Summary of the eruptive history of Mount Mazama
-- Modified from: Bacon, 1983
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The history displayed in the caldera walls begins with construction of the
andesitic Phantom Cone, approximately 400,000 years B.P. Subsequently, at least
6 major centers erupted combinations of mafic andesite, andesite, or dacite
before initiation of the Wisconsin Glaciation approximately 75,000 years B.P.
Eruption of andesitic and dacitic lavas from 5 or more discrete centers, as well
as an episode of dacitic pyroclastic activity, occurred until approximately
50,000 years B.P.; by that time, intermediate lava had been erupted at several
short-lived vents. Concurrently, and probably during much of the Pleistocene,
basaltic to mafic andesitic monogenetic vents built cinder cones and erupted
local lava flows low on the flanks of Mount Mazama. Basaltic magma from one of
these vents, Forgotten Crater, intercepted the margin of the zoned intermediate
to silicic magmatic system and caused eruption of commingled andesitic and
dacitic lava along a radial trend sometime between approximately 22,000 and
30,000 years B.P. Dacitic deposits between 22,000 and 50,000 years old appear
to record emplacement of domes high on the south slope. A line of silicic domes
that may be between 22,000 and 30,000 years old, northeast of and radial to the
caldera, and a single dome on the north wall were probably fed by the same
developing magma chamber as the dacitic lavas of the Forgotten Crater complex.
The dacitic Palisade flow on the northeast wall is approximately 25,000 years
old. These relatively silicic lavas commonly contain traces of hornblende and
record early stages in the development of the climatic magma chamber.
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Some 15,000 to 40,000 years were apparently needed for development of the
climactic magma chamber, which had begun to leak rhyodacitic magma by 7015 +/-
45 years B.P. Four rhyodacitic lava flows and associated tephras were emplaced
from an arcuate array of vents north of the summit of Mount Mazama, during a
period of approximately 200 years before the climactic eruption. The climactic
eruption began 6845 +/- 50 years B.P., with voluminous airfall deposition from a
high column, perhaps because ejection of approximately 4-12 cubic kilometers of
magma to form the lava flows and tephras depressurized the top of the system to
the point where vesiculation at depth could sustain a Plinian column. Ejecta of
this phase issued from a single vent north of the main Mazama edifice but within
the area in which the caldera later formed. The Wineglass Welded Tuff of
Williams (1942) is the proximal featheredge of thicker ash-flow deposits
downslope to the north, northeast, and east of Mount Mazama and was deposited
during the single-vent phase, after collapse of the high column, by ash flows
that followed topographic depressions. Approximately 30 cubic kilometers of
rhyodacitic magma were expelled before collapse of the roof of the magma chamber
and inception of caldera formation ended the single-vent phase. Ash flows of
the ensuing ring-vent phase erupted from multiple vents as the caldera
collapsed. These ash flows surmounted virtually all topographic barriers,
caused significant erosion, and produced voluminous deposits zoned from
rhyodacite to mafic andesite. The entire climactic eruption and caldera
formation were over before the youngest rhyodacitic lava flow had cooled
completely, because all the climactic deposits are cut by fumaroles that
originated within the underlying lava, and part of the flow oozed down the
caldera wall.
-
A total of approximately 51-59 cubic kilometers of magma was ejected in the
precursory and climactic eruptions, and approximately 40-52 cubic kilometers of
Mount Mazama was lost by caldera formation. The spectacular compositional
zonation shown by the climactic ejecta -- rhyodacite followed by subordinate
andesite and mafic andesite -- reflects partial emptying of a zoned system,
halted when the crystal-rich magma became too viscous for explosive
fragmentation. This zonation was probably brought about by convective
separation of low-density, evolved magma from underlying mafic magma.
Confinement of postclimactic eruptive activity to the caldera attests to
continuing existence of the Mazama magmatic system. ...
-
The age of the lower pumice fall (Llao vent)
is 7015 +/- 45 years, on the basis of
radiocarbon dating of carbonized twig fragments from the upper (approximately) 1
centimeter of a 15-centimeter-thick soil developed on glacial drift beneath the
deposit at the Wineglass. ...
Ash beds that are apparently correlative with the lower pumice fall
are present in northern Washington (Mack, et.al., 1979), approximately 700
kilometers (435 miles) from Crater Lake, in eastern Washington (Blinman, et.al.,
1979), near Steens Mountain, southeastern Oregon (Blinman, et.al., 1979;
P.J.Mehringer, oral commun., 1982), and in the Lake Lahontan area, western
Nevada (Tsoyawata Bed of Davis, 1978; J.O. Davis, written commun., 1982). The
lower pumice fall must have been deposited over a period of at least several
days in order for sufficient variation in wind direction to occur to account for
the wide dispersal. The volume of magma equivalent to the lower pumice fall
deposits is probably around 2-10 cubic kilometers. ...
-
The climactic, caldera-forming eruption of Mount Mazama
(6,845 +/- 50 years B.P.)
can be divided into two
phases: single vent and ring vent. Onset of collapse of the caldera probably
caused the switch from the first to the second phase of eruption; the timing of
this switch can be documented through stratigraphic relations. ...
Deposits of the single-vent phase consist of two units erupted successively from
the same vent area: the
climactic pumice fall
and the Wineglass Welded Tuff of Williams (1942).
The climactic pumice fall represents air-fall
deposition from a high Plinian column; the Wineglass Welded Tuff was deposited
by ash flows derived from a collapsed column. ...
Deposits of the climactic pumice fall account for a large part of the
material erupted during the single-vent phase. ...
-
The widespread Mazama tephra has been used extensively as a stratigraphic
marker. Much of the climactic pumice fall
was carried to the northeast; only
sparse, thin patches of redeposited pumice are present near the caldera rim
around the southwest quadrant. The informally-named Mazama ash is
>50 centimeters thick (20 inches)
at Newberry Volcano, 110 kilometers (68 miles)
from Crater Lake,
and >1 centimeter thick (less than 1/2 inch)
in southwestern Saskatchewan, 1,200 kilometers
(745 miles) from its source. ...
-
MORE Mazama Ash Information
Post-Climactic Eruption Activity -
Wizard Island and Merriam Cone
|
-
-
CraterLake82_crater_lake_and_wizard_island_09-82.jpg
Crater Lake and Wizard Island.
USGS Photograph taken in September 1982 by Lyn Topinka.
[medium size] ...
[large size]
From: U.S. National Park Service, Crater Lake National Park Website, 2001
-
Following the collapse of Mount Mazama, lava poured into the
caldera even as the lake began to rise. Today, a small volcanic
island, Wizard Island, appears on the west side of the lake.
This cinder cone rises 760 feet (233 meters) above the lake
and is surrounded by black volcanic lava blocks. A small crater,
300 feet (90 meters) across and 90 feet (27 meters) deep,
rests on the summit. The crater is filled by snow during the
winter months, but remains dry during the summer.
From:
Foxworthy and Hill, 1982,
USGS Open-File Report 1249
-
From a probable altitude of roughly 12,000 feet, the top of former Mount Mazama
was lost to eruption and collapse that left the present huge
crater and the deepest lake (Crater Lake - 1,932 feet) in North America.
Explosive eruptions built Wizard Island (at least 800-900 years
ago) and two other cones (submerged) on present crater floor.
From:
Bacon, 1983,
Eruptive History of Mount Mazama and Crater Lake Caldera, Cascade Range, U.S.A.:
Journal of Volcanology and Geothermal Research, v.18, p.57-115
-
The only volcanic features in the Crater Lake area younger than the
climactic eruption occur within the caldera. Williams (1961) interpreted the
geology of the caldera floor on the basis fo bathymetric data obtained by the
U.S. Coast and Geodetic Survey (1959) and samples dredged by Nelson (1961). No
subaerial tephra deposits correlative with postcaldera events have been
recognized. Recent investigations (Nelson, 1967; Nelson et.al., 1980; Williams
and Von Herzen, 1983) lead to some important revisions.
-
Merriam Cone, a small (approximately 0.1 cubic kilometer) olivine-bearing
andesitic vent on the north margin of the caldera floor, is the smallest of
three distinguishable volcanic features. The caldera floor partly surrounding
Merriam Cone owes its comparatively flat surface to sedimentary fill (Nelson,
et.al., 1980), not to lava flows, as suggested by Williams (1961).
Wizard Island
forms the subaerial part of a voluminous pile of presumably similar
andesitic material.
The Wizard Island edifice accounts for approximately 1 to 2 cubic
kilometers of magma, depending on where its base is drawn. Like Merriam Cone,
the Wizard Island andesitic magmas were erupted near the inferred structural
margin of the caldera.
-
The broad
platform east of Wizard Island suggests silicic lava flows or coalescing domes.
At the west end of this platform is a small dome composed of hornblende
rhyodacite. The bathymetric map suggests that the platform may extend beneath
the north side of the Wizard Island pile. Nelson (1961), however, did not
report any Wizard Island tephra in dredge hauls from the platform or the
rhyodacite dome, and so it may be that some silicic volcanism occurred after the
last andesitic eruptions. The volume of silicic lava erupted was between
approximately 0.5 and 2 cubic kilometers, depending on tis extent beneath and
west of the dome. Erupted inboard of the two andesitic centers, the rhyodacite
is about as differentiated as the most evolved magma of the climactic chamber
(Bacon and Smith, unpubl.data, 1981). The postcaldera rhyodacite may represent
either (1) uppermost climactic magma, which escaped eruption prior to formation
of the caldera, or (2) the first leak from a new batch of silicic magma
regenerated after the climactic eruption. ...
-
Whatever the ages, relative or absolute, of the postcaldera eruptive units the
Mazama magmatic system apparently remains the focus of volcanic activity for a
large region.
Areas of very high heat flow on the caldera floor provide evidence for
ongoing hydrothermal circulation (Williams and Von Herzen, 1983), and the
elevated chloride and sodium contents of lake water relative to other surface
waters may indicate a component of geothermal fluid (J.M.Thompson, unpubl. data,
1981; Williams and Von Herzen, 1983).
From:
Bacon, Mastin, Scott, and Nathenson, 1997,
Volcano and Earthquake Hazards in the Crater Lake Region, Oregon:
USGS Open-File Report 97-487
-
[Map,25K,InlineGIF]
Geologic Map of Crater Lake Caldera Floor
-- Modified from: Bacon, et.al., 1997,
USGS Open-File Report 97-487
From:
Tilling, 1985,
Volcanoes: USGS General Interest Publication, p.11-12.
-
An interesting variation of a
composite volcano
can be seen at
Crater Lake
in Oregon. From what geologists can interpret of its past, a high volcano --
called Mount Mazama -- probably similar in appearance to
present-day Mount Rainier was once located at this spot.
Following a series of
tremendous explosions about 6,600 years ago,
the volcano lost its top. Enormous volumes of
volcanic ash and dust were expelled and swept down the slopes as ash flows and
avalanches. These large-volume explosions rapidly drained the lava beneath the
mountain and weakened the upper part. The top then collapsed to form a
large depression,
which later filled with water and is now completely occupied by beautiful
Crater Lake.
A last gasp of eruptions produced a small cinder cone
which rises above the water surface as Wizard Island in,
and near the rim, of the lake.
From:
Wood and Kienle, 1990,
Volcanoes of North America: United States and Canada:
Cambridge University Press, 354p., p.193-195,
Contribution by Charles R. Bacon
-
Crater Lake
caldera
formed by collapse during the catastrophic eruption of approximately 50 cubic
kilometers of magma, 6,845 carbon-14 years B.P. (before present). The 8x10
kilometer caldera lies in the remains of Mount Mazama, a
Pleistocene
stratovolcano cluster
covering 400 square kilometers in the
southern Oregon Cascades. ...
-
Post-caldera volcanic landforms are present beneath the lake surface and poke
through to form Wizard Island. The central platform,
Merriam Cone, and Wizard Island are all andesite evidently
erupted within a few hundred years of caldera collapse. The small rhyodacite
dome 30 meters belows lake level one kilometer east of Wizard Island is the
youngest feature.
From:
Bacon, Charles R., 1983,
Eruptive History of Mount Mazama and Crater Lake Caldera, Cascade Range,
U.S.A.:
Journal of Volcanology and Geothermal Research, v.18 (1983), p.57-115
-
The only volcanic features in the Crater Lake area younger than the
climactic eruption occur within the caldera. ...
Merriam Cone, a small (approximately 0.1 cubic kilometer) olivine-bearing
andesitic vent on the north margin of the caldera floor, is the smallest of
three distinguishable volcanic features. ... Wizard Island forms the
subaerial part of a voluminous pile of presumably similar andesitic material.
The Wizard Island edifice accounts for approximately 1 to 2 cubic
kilometers of magma, depending on where its base is drawn. ... The broad
platform east of Wizard Island suggests silicic lava flows or coalescing domes.
At the west end of this platform is a small dome composed of hornblende
rhyodacite. ...
From:
U.S. National Park Service, Crater Lake National Park Website, 2001
-
Lake researchers have discovered two areas on the lake
bottom affected by hydrothermal spring water. Mineral-rich
water, at a slightly elevated temperature, pools in some
locations and leaves iron deposits in others. Communities of
bacteria mark the venting sites.
Volcano and Hydrologic Monitoring
|
From:
Iwatsubo, et.al., 1988,
Measurements of slope distances and zenith angles at Newberry and South Sister
volcanoes, Oregon, 1985-1986:
USGS Open-File Report 88-377, 51p.
-
Between 1980 and 1984, the U.S. Geological Survey's David A. Johnston Cascades
Volcano Observatory (CVO) established baseline geodetic networks at
Mount Baker,
Mount Rainer, and
Mount St. Helens in Washington,
Mount Hood and
Crater Lake in Oregon, and
Mount Shasta and
Lassen Peak in California.
To this list of
potentially active volcanoes, CVO extended its monitoring program in 1985 to
include
Newberry and
South Sister
volcanoes in central Oregon. The Newberry and
South Sister networks were re-measured in 1986 and will be measured periodically
in future years. Improvements since 1984 in the recording of endpoint and
flightline temperatures resulted in better overall data than obtained
previously. The improvements included: calibration of all the sensors and
precision thermistors, installation of a new recording system for flightline
data, and recording of endpoint temperatures 6 meters above ground level. The data
collected in 1985 and 1986 indicate little or no apparent deformation at either
volcano between surveys.
From:
University of Washington's Geophysics Program Website, 2001
-
In addition to locating regional earthquakes, the
Pacific Northwest Seismograph Network (PNSN),
in cooperation with the Cascades Volcano Observatory,
is also responsible for monitoring seismic activity at volcanoes in the Pacific Northwest.
The PNSN currently operates seismometers on or near Mount Adams, Mount Rainier,
Mount St. Helens, Mount Hood, Mount Baker, Three Sisters, and Crater Lake.
-
Crater Lake Monitoring Menu
Crater Lake National Park
|
From:
U.S. National Park Service Website: Crater Lake National Park, 1999
-
Crater Lake National Park
attracts approximately 500,000 visitors per year,
with the high season being July and August.
Crater Lake National Park is located in southern Oregon
on the crest of the Cascade Range, 100 miles from the Pacific coast.
The National Park was established in 1902 and encompases 183,244 square miles.
The 33-mile Rim Drive around Crater Lake is a two lane road
that has more than 20 scenic overlooks.
From mid-October until mid-June, the north entrance and
Rim Drive are closed to the public due to deep snow and
ice buildups along the road. Rim Drive around the east
side of the lake can be closed earlier than mid-October
and may not open until July. Deer and other wildlife
crossing the road and icy conditions at any time of the
year provide hazards to drivers.
From:
Wood and Kienle, 1990, Volcanoes of North America: United States and Canada:
Cambridge University Press, 354p., p.193-195,
Contribution by Charles R. Bacon
-
Crater Lake National Park is accessible from the south and north via Oregon Highways 62 and
138, respectively. A paved road runs around the caldera rim. Access to the lake is limited to
the trail at Cleetwood Cove, where tour boats provide a good close-up view of the caldera walls.
-
"Visit A Volcano" - Crater Lake National Park
Crater Lake National Park - Points of Interest
|
-
[Map,24K,InlineGIF]
Geologic Map, Crater Lake Caldera Floor and Caldera Walls, with Points of Interest
-- Modified from:
Bacon, et.al., 1997, USGS Open-File Report 97-487
-
-
- Geologic evidence for the rapid formation of Crater Lake caldera by
catastrophic collapse during the climactic eruption of Mount Mazama
indicates that most of the caldera wall dates from that time. However, the
bench on the south wall, informally known as Chaski slide, wall-parallel
lake-facing scarps near Garfield Peak, and similar faults mapped in the
Sun Notch to Eagle Point area suggest that large blocks of the
south wall have the potential to fail. Nelson and other (1988, 1994)
described a landslide deposit on the lake
floor from Chaski Bay to the center of the lake that apparently formed
soon after the caldera collapse and the central platform volcano erupted but
before a deep lake was present.
-- Excerpt from:
Bacon, et.al., 1997,
Volcano and Earthquake Hazards in the Crater Lake Region, Oregon:
USGS Open-File Report 97-487
-
- Within 200 years of the eruption at Llao Rock, another
thick lava flow erupted near present-day Cleetwood Cove.
-- From: Klimasauskas, et.al., 2002
-
-
- Generous amounts of winter snow, averaging 533 inches
(1,354 centimeters) per year, supply the lake with water. There are no
inlets or outlets to the lake. Crater Lake, at 1,958 feet (597
meters) deep, is the seventh deepest lake in the world and the
deepest in the United States. Evaporation and seepage
prevent the lake from becoming any deeper.
The lake averages more than five miles (8 kilometers) in diameter,
and is surrounded by steep rock walls that rise up to 2,000 feet
(600 meters) above the lake's surface.
-- Excerpt from: U.S. National Park Service, Crater Lake National Park Website, 2001
-
-
- Discovery Point is the site of John Wesley Hillman's "discovery" of Crater Lake in
1853.
-- Excerpt from: U.S. National Park Service, Crater Lake National Park Website, 2001
-
- Grouse Hill and Redcloud Cliff are thick lava flows erupted
between 30,000 and 25,000 years ago.
-- Klimasauskas, et.al., 2002
-
-
- Hillman Peak is the westernmost andesitic stratocone
in the cluster of polygenetic volcanoes that make up
Mount Mazama.
-- Excerpt from:
Bacon, Charles R., 1983,
Eruptive History of Mount Mazama and Crater Lake Caldera, Cascade Range,
U.S.A.:
Journal of Volcanology and Geothermal Research, v.18 (1983), p.57-115
- Hillman Peak is
1,980 feet (604 meters) above the water, highest point on the caldera rim
-- Excerpt from: U.S. National Park Service, Crater Lake National Park Website, 2001
- Individual stratovolcanoes and shields that make up
Mount Mazama become younger in a west-northwest sense.
The oldest Mazama lavas dated are flows near lake
level at Phantom Ship
and the lavas of Mount Scott (around 400,000 years). The youngest
stratovolcano is Hillman Peak (around 70,000 years). Local andesite
flows on the north rim are 50-40,000 years old.
-- Excerpt from:
Wood and Kienle, 1990,
Volcanoes of North America: United States and Canada:
Cambridge University Press, 354p., p.193-195,
Contribution by Charles R. Bacon
-
- 7,900 years ago, a white layer of
pumice and ash and the thick lava flow of Llao Rock.
-- From: Klimasauskas, et.al., 2002
-
-
- Palisade Point
is 507 feet (155 meters) above the water, lowest point on the caldera rim
-- Excerpt from: U.S. National Park Service, Crater Lake National Park Website, 2001
-
-
- Individual stratovolcanoes and shields that make up
Mount Mazama become younger in a west-northwest sense.
The oldest Mazama lavas dated are flows near lake
level at Phantom Ship
and the lavas of Mount Scott (around 400,000 years). The youngest
stratovolcano is Hillman Peak (around 70,000 years). Local andesite
flows on the north rim are 50-40,000 years old.
-- Excerpt from:
Wood and Kienle, 1990,
Volcanoes of North America: United States and Canada:
Cambridge University Press, 354p., p.193-195,
Contribution by Charles R. Bacon
- Phantom Ship is 167 feet (51 meters) above the water.
-- Excerpt from: U.S. National Park Service, Crater Lake National Park Website, 2001
-
- Grouse Hill and Redcloud Cliff are thick lava flows erupted
between 30,000 and 25,000 years ago.
-- Klimasauskas, et.al., 2002
-
-
- Individual stratovolcanoes and shields that make up
Mount Mazama become younger in a west-northwest sense.
The oldest Mazama lavas dated are flows near lake
level at Phantom Ship
and the lavas of Mount Scott (around 400,000 years). The youngest
stratovolcano is Hillman Peak (around 70,000 years). Local andesite
flows on the north rim are 50-40,000 years old.
-- Excerpt from:
Wood and Kienle, 1990,
Volcanoes of North America: United States and Canada:
Cambridge University Press, 354p., p.193-195,
Contribution by Charles R. Bacon
- Mount Scott - highest peak in the park, historic fire tower, strenuous climb,
1,500 foot rise.
-- Excerpt from:
U.S. National Park Service, Crater Lake National Park Website, January 2001
-
Wizard Island and Merriam Cone
|
-
- From a probable altitude of roughly 12,000 feet, the top of former Mount Mazama
was lost to eruption and collapse that left the present huge
crater and the deepest lake ( Crater Lake - 1,932 feet) in North America.
Explosive eruptions built Wizard Island (at least 800-900 years
ago) and two other cones (submerged) on present crater floor.
-- Excerpt from: Foxworthy and Hill, 1982
- The only volcanic features in the Crater Lake area younger than the
climactic eruption
occur within the caldera. ...
Merriam Cone, a small (approximately 0.1 cubic kilometer) olivine-bearing
andesitic vent on the north margin of the caldera floor, is the smallest of
three distinguishable volcanic features. ... Wizard Island forms the
subaerial part of a voluminous pile of presumably similar andesitic material.
The Wizard Island edifice accounts for approximately 1 to 2 cubic
kilometers of magma, depending on where its base is drawn. ... The broad
platform east of Wizard Island suggests silicic lava flows or coalescing domes.
At the west end of this platform is a small dome composed of hornblende
rhyodacite.
-- Excerpts from:
Bacon, Charles R., 1983,
Eruptive History of Mount Mazama and Crater Lake Caldera, Cascade Range,
U.S.A.:
Journal of Volcanology and Geothermal Research, v.18 (1983), p.57-115
- Following the collapse of Mount Mazama, lava poured into the
caldera even as the lake began to rise. Today, a small volcanic
island, Wizard Island, appears on the west side of the lake.
This cinder cone rises 760 feet (233 meters) above the lake
and is surrounded by black volcanic lava blocks. A small crater,
300 feet (90 meters) across and 90 feet (27 meters) deep,
rests on the summit. The crater is filled by snow during the
winter months, but remains dry during the summer.
-- Excerpt from: U.S. National Park Service, Crater Lake National Park Website, 2001
- See "Post-Climactic Eruption" above for MORE Wizard Island and Merriam Cone information
Return to:
[Crater Lake Menu] ...
[Crater Lake "Visit A Volcano" Menu] ...
[Crater Lake Eruptive History Menu] ...
[Oregon Volcanoes and Volcanics Menu] ...
URL for CVO HomePage is:
<http://vulcan.wr.usgs.gov/home.html>
URL for this page is:
<http://vulcan.wr.usgs.gov/Volcanoes/CraterLake/description_crater_lake.html>
If you have questions or comments please contact:
<GS-CVO-WEB@usgs.gov>
04/18/08, Lyn Topinka