America's Volcanic Past -
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| "Though few people in the United States may actually experience an erupting volcano, the evidence for earlier volcanism is preserved in many rocks of North America. Features seen in volcanic rocks only hours old are also present in ancient volcanic rocks, both at the surface and buried beneath younger deposits." -- Excerpt from: Brantley, 1994 |
Volcanic Highlights and Features:
[This list is just a sample of
various Oregon volcanic features or events and is by no means inclusive.]
Idaho, Oregon, and Washington:
Oregon:
Excerpts from: R. L. Whitehead, 1994, Ground Water Atlas of the United States: Idaho, Oregon, Washington: U.S. Geological Survey HA730-H; and U.S. Forest Service Website, Deschutes and Ochoco National Forests, 2001 |
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Cascade Range Region:20
Where the Sierra Nevada ends a chain of
explosive volcanic centers, the Cascade volcanoes,
begins. The Cascades Province forms an arc-shaped
band extending from British Columbia to Northern
California, roughly parallel to the Pacific coastline.
Within this region, 13 major volcanic centers lie in
sequence like a string of explosive pearls.
Although the largest volcanoes like Mount St.
Helens get the most attention, the Cascades is really made up of a band of thousands of
very small, short-lived volcanoes that have built a platform of lava and volcanic debris.
Rising above this volcanic platform are a few strikingly large volcanoes that dominate the
landscape.
Columbia Plateau:20 The Columbia Plateau province is enveloped by one of the worlds largest accumulations of lava. Over 500,000 square kilometers of the Earth's surface is covered by it. The topography here is dominated by geologically young lava flows that inundated the countryside with amazing speed, all within the last 17 million years. Over 170,000 cubic kilometers of basaltic lava, known as the Columbia River basalts, covers the western part of the province. These tremendous flows erupted between 17-6 million years ago. Most of the lava flooded out in the first 1.5 million years -- an extraordinarily short time for such an outpouring of molten rock. It is difficult to conceive of the enormity of these eruptions. Basaltic lava erupts at no less than about 1100 degrees C. Basalt is a very fluid lava; it is likely that tongues of lava advanced at an average of 5 kilometers/hour -- faster than most animals can run. Whatever topography was present prior to the Columbia River Basalt eruptions was buried and smoothed over by flow upon flow of lava. Over 300 high-volume individual lava flows have been identified, along with countless smaller flows. Numerous linear vents, some over 150 kilometers long, show where lava erupted near the eastern edge of the Columbia River Basalts, but older vents were probably buried by younger flows. Basin and Range:20 The Basin and Range province has a characteristic topography that is familiar to anyone who is lucky enough to venture across it. Steep climbs up elongate mountain ranges alternate with long treks across flat, dry deserts, over and over and over again! This basic topographic pattern extends from eastern California to central Utah, and from southern Idaho into the state of Sonora in Mexico. Within the Basin and Range Province, the Earth's crust (and upper mantle) has been stretched up to 100% of its original width. The entire region has been subjected to extension that thinned and cracked the crust as it was pulled apart, creating large faults. Along these roughly north-south-trending faults mountains were uplifted and valleys down-dropped, producing the distinctive alternating pattern of linear mountain ranges and valleys of the Basin and Range province. |
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Rocks of Idaho, Oregon, and Washington State:23
Unconsolidated Deposits:23
Volcanic Rocks:23
Pre-Miocene Undifferentiated Rocks:23
Miocene Volcanic Rocks:23
Miocene Basaltic-Rock Aquifers:23
Pliocene and Younger Volcanic Rocks:23
Silicic Volcanic Rocks:23
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| Oregon's Cascade Range Volcanoes |
Cascade Range in Oregon:1
The Cascade province is actually made up of two
volcanic regions, the older, broader, and deeply
eroded Western Cascades and the dominating,
snow-capped peaks of the younger, more easterly
volcanoes of the High Cascades, such as Mount
Hood, Mount Jefferson, and the Three Sisters (North,
Middle, and South Sister). Another High Cascade
peak, Mount Mazama, was destroyed about 6,800
years ago by a catastrophic eruption that left a deep
caldera later filled by what is now Crater Lake.
(See Individual Volcanoes below)
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| Oregon's Volcanic Gemstone - Thundereggs |
Oregon's State Rock:21
Oregon's State rock, the "thunderegg,"
may be the best known gem material from Oregon.
Thundereggs were not, as believed by some people,
ejected from volcanoes, but formed in very
soft and friable volcanic ash beds.
Solutions containing silica permeated
the cinders until favorable points
for chalcedony deposition were achieved.
Aggregations of chalcedony were deposited,
but before the material could fully
solidify the center of the
concretion split apart, possibly because
of shrinkage, permitting the later
introduction of additional materials.
The resulting star-shaped centers of
chalcedony may be in the form of agate,
jasper, or in some cases different varieties of opal.
Thundereggs are used in a number of ways.
One of the most common uses is to simply
saw the thunderegg into two pieces,
polish the sawed face of
each half, and use it as a display or
decorative piece; bookends are also made
in this fashion. Also, the thundereggs are
sawed into slabs from which
calibrated and freeform cabochons are cut.
Additionally, at least one firm in the
United States is manufacturing gem
spheres from thundereggs.
| Battle Ax Mountain |
Battle Ax Mountain:4
Battle Ax Mountain is a 1-2 million years old shield volcano that surmounts a high ridge north of Detroit, Oregon. Battle Ax erupted chiefly andesite lava, though its flows range from basaltic andesite to dacite.
| Belknap Shield Volcano |
Belknap Shield Volcano:5
One type of basaltic activity is characterized by
the concentration of many tephra and lava-flow
eruptions at a central vent and several flank vents.
This type of activity has built shield volcanoes
typically 5-15 kilometers in diameter and several hundred meters to
more than 1000 meters high. Many have summit cinder cones.
Belknap in central Oregon
is the youngest such shield volcano in the Cascades and has lava flows
as young as 1,400 years.
| Benham Falls |
Benham Falls:16
The most recent fundamental change to the
Upper Deschutes River came 7000 years ago from the
eruption of the Lava Butte Lava Flow from
Newberry Volcano. The lava built a high dam against Benham
Butte and denied the river its old channel
east of the butte. Water backed up behind the lava dam nearly to
Pringle Falls until the new lake overtopped
and flowed through a low saddle at Benham Butte. Thus began
Benham Falls and a new channel of the
Deschutes River. From Benham Falls to Lava Island Falls, the
location and character of the
Deschutes River changed radically,
the new channel followed the west edge of
the lava to Lava Island Falls.
Above Benham Falls, the old channel, 100 feet deeper than the present
channel, slowly filled with sediment.
| Blue Lake (Central Oregon) |
Blue Lake:29
Blue Lake is situated in the
Deschutes National Forest one-half mile west of Suttle
Lake. Blue Lake is a natural lake located
at an elevation of 3,453 feet. It is a relatively
small lake covering 54 surface acres,
but has a maximum depth of 314 feet. Because of its
great depth and intense blue color,
it is often called the "Crater Lake of the Central Oregon
Cascades". Only three percent of the
lake's surface area is less than 10 feet deep and the
average depth is 140 feet. The shoreline is 1.3 miles in length.
Blue Lake was formed by a volcanic explosion
which occurred when hot volcanic
magma came into contact with ground water.
Radiocarbon dating reveals the formative
blast occurred about 3,500 years ago.
Land adjacent to the lake consists of forested slopes
that are extremely steep; much of which
is actually part of the original explosion crater that
holds the lake. The drainage for Blue Lake
covers 17 square miles. Water sources include
snowmelt runoff from the surrounding slopes,
and one intermittent stream entering from
the northwest. The source of most of
Blue Lake's water is from large springs located 240
feet below the water surface near the east shore.
| Blue Mountains |
Blue Mountains:16
The Blue Mountains are a complex of mountain ranges and intermontane basins and valleys which extend from the northeast corner of
Oregon southwestward into Central Oregon near Prineville. The Blue Mountains are not a cohesive range but a cluster of smaller ranges
of varying relief and
orientation. The western portion of the province is part of a wide uplifted plateau, while the eastern section contains a striking array of ice
sculpted mountain peaks, deep canyons, and broad valleys. In Central Oregon the Ochoco Mountains form the western end of the
province.
The unique aspect of the Blue Mountains province is that it is a patchwork of massive pieces of the earth's crust. Permian, Triassic, and
Jurassic rocks (300 to 200 million years old) were transported by the Pacific Plate and accreted to the late Mesozoic shoreline, which
at that time (about a 100 million years ago) lay across what is today eastern Washington and Idaho. Following the accretion of the
terranes there was a vast shallow seaway during covering much of the area during the remainder of the Mesozoic and then slow uplift
began. From about 50 to 37 million years ago, eruptions of volcanoes in the western part of the province formed the Clarno Formation.
From 37 to 17 million years ago eruptions in the Western Cascades spread ash across the province to form the John Day Formation.
From 17 to 14 million years ago major basaltic eruptions covered much of the province with basalt flows to form the Columbia River
Group. Continued faulting and uplift has resulted in a deeply eroded landscape.
In Central Oregon, at the western end of the province, some deposits of middle Cretaceous age are exposed in the Mitchell area but
predominately the area is made up of Tertiary volcanics of the Clarno and John Day Formations and the Columbia River Group.
| Broken Top |
Broken Top:26
Broken Top is a complex stratovolcano
magnificently exposed by glacial erosion.
(Also see Three Sisters Region below)
| Brown Mountain |
Brown Mountain:17
Brown Mountain is a small (5 cubic kilometers),
youthful-looking shield topped by a cinder cone whose central depression is
15 meters deep. Much of the mountain is bare, unweathered,
dark-colored, block-lava and clinkery aa flows. The flows are
mostly olivine-bearing basaltic andesite and andesite in composition.
At first glance Brown Mountain looks no older than a few thousand years.
However, a small glacial valley carved into the
northeast flank and a cirque gouged out of the summit
cinder cone belie its youthful appearance. The deposits left behind have
features typical of glacial deposits from approximately 13,000 years ago.
Evidence of the next older glaciation is missing, and the
age of Brown Mountain can be bracketed between around 60,000 and 12,000 years.
A climb to the summit of Brown Mountain is mostly a scramble
over fresh talus as there is no maintained trail to its summit.
Because its summit is lower than that of nearby peaks,
views from Brown Mountain are not as spectacular. However, it offers a
close view of the south flanks of Mount McLoughlin.
| Cascade-Siskiyou National Monument |
Cascade-Siskiyou National Monument:25
Geological and climatological influences
from the north, south, east and west converge
in southwestern Oregon's Cascade, Siskiyou and
Klamath mountain ranges. Plants and animals
typically found in ecologically
distinct regions come together in a spectacular
array of species richness and diversity. The
Cascade-Siskiyou National Monument represents the
heart of this remarkable region.
The Cascade-Siskiyou National Monument
belongs to BLM's new National
Landscape Conservation System (NLCS).
The BLM recently established the
NLCS to focus attention on some of the
nation's most remarkable and rugged
landscapes in the West. Through the NLCS,
the BLM hopes to increase the public's
awareness of and appreciation for these
public land treasures, and to focus more
management attention and resources on them.
National Monuments managed under
the NLCS will have different regulations than those
administered by the National
Park Service.
Pilot Rock:25
Pilot Rock, the remnant of an ancient volcano,
stands out as one of the Monument's most striking
features. Visible from much of the Shasta Valley in
northern California, and parts of Oregon's Rogue
Valley, the rock provides viewers with a look at the
inside of a volcano. Over time, the exterior volcano
eroded away, leaving behind the now cooled
magma of the ancient volcano's central vent. Fossil
sites in the vicinity of Pilot Rock contain leaf
impressions and conifer cones that became
embedded in volcanic ash beds 25-35 million years
ago.
| Central Oregon High Cascades |
High Lava Plains:1
This area has some of the most recent faulting and
youngest volcanic activity in Oregon.
Well-preserved in a high desert climate, volcanic
features stand out about the plains.
Central Oregon High Cascades:16
The Cascades have grown in several episodes of volcanism from
40 million years to the present. The last two
episodes created the view of the Cascades seen from eastern Oregon
(from about 8 to 5 million years, and from
about 2 million years to the present).
The most recent episode of volcanism produced the High Cascades
and the high volcanic peaks perched on the
crest such as the Three Sisters, Broken Top, and Mount Jefferson.
The High Cascades consist mostly of large
numbers of overlapping shield volcanoes. An excellent example of a
shield volcano is Belknap Crater volcano along
the McKenzie Pass Highway (State Highway 242).
At McKenzie Pass, great fields of rough, black lava, 1,500
years old, form a flattened cone 4 miles in
diameter with Belknap Crater at its center. Some lava has flowed
many miles beyond the cone. Elsewhere in the
Cascades the chemistry of the lavas and short length of lava flows
created much steeper and taller cones such as
Black Butte and Odell Butte. South Sister, Broken Top, Mount
Jefferson, and several other peaks have a more complex volcanic history.
| Columbia Plateau |
Columbia Plateau1
Between 14 and 16 million years ago, "fissure" volcanic eruptions
in eastern Washington, eastern
Oregon, and western Idaho produced enormous
volumes of molten Columbia River
basalt that flowed
like water west into the Deschutes-Columbia
Plateau province in eastern Washington and
northeastern Oregon, with some lava continuing to
flow as far west as the Pacific Ocean via the
ancestral Columbia River valley. As the basalt
cooled and congealed, it formed the columnar cliffs
that dominate the landscape today. Erosions by the
Columbia River has exposed a particularly
spectacular sequence of these rocks in the
Columbia River Gorge on Oregon's northern
boundary.
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| Columbia River Gorge |
Columbia River Gorge:13
During the Miocene period (17-12 million years ago),
unusual volcanoes,
called basalt floods, erupted in eastern Washington
and Oregon. These volcanoes were cracks in the earth's crust,
several miles long, which poured out floods of liquid molten rock.
41,000 cubic miles (170,000 cubic kilometers) of this
lava spread to cover large parts of Oregon and Washington. Out of 270 lava
flows that spread across the region, 21 poured through the
Gorge forming layers of rock up to 2,000 feet
(600 meters) deep.
|
Crater Lake -
Crater Lake National Park |
Crater Lake:11
Today, the calm beauty of Crater Lake belies the violent earth forces
that formed the lake. Crater Lake lies
inside the top of an ancient volcano known as Mount Mazama.
For half a million years this mighty volcano produced massive eruptions
interrupting long periods of quiet. Ash, cinders, and pumice exploded upward,
building the mountain to a height of about 12,000 feet.
About 7,700 years ago the climatic eruptions of Mount Mazama occurred.
Ash from these eruptions lies scattered over eight states and three Canadian
provinces, some 5,000 square miles were covered with 6 inches of Mazama's ash.
In the park's Pumice Desert ash lies 50 feet deep. The eruptions were
42 times greater than those of Mount St. Helens in 1980. The Mazama
magma chamber was emptied and the volcano collapsed, leaving a huge bowl-shaped
caldera.
The collapse of Mount Mazama marked the beginning of the formation of Crater Lake.
Snow and rain fell into the 3,000-foot deep hole, filling the collapsed structure.
Eventually, the lake reached a relatively constant level. Precipitation entering
the lake was offset by evaporation and seepage. Today, the lake level only
varies about three feet each year.
Crater Lake, at 1,958 feet (597 meters) deep,
is the seventh deepest lake in the world and the deepest in the
United States.
Wizard Island:18
Smaller eruptions about 5,000 years ago formed Wizard Island
and a lava dome on the lake floor.
|
Crater Lake National Park:18
Crater Lake occupies a 6-mile-wide caldera.
| Davis Lake |
Davis Lake:16
About 5,000 years ago the eruption of the
Davis Lake Lava Flow dammed Odell Creek to form
Davis Lake.
| Devils Garden |
Devils Garden:19
The Devils Garden lava field is rich in excellent examples of lava flow and vent features. An area of 117 square kilometers is covered by multiple flows of fresh, inflated, pahohoe lava that erupted from fissure vents in the northeast part of the Devils Garden. Several rounded hills and higher areas of older rocks are now kipukas completely surrounded by the black, basaltic lava.
The main vent from which all the lava issued is surrounded by a low spatter rampart, but other vents along the fissure to the south are marked by well-preserved spatter cones, two of which, "The Blowouts", are exceptionally large. The spatter cones range 1 to 30 meters in height, and 2 to 150 meters in diameter.
The age of the Devils Garden lava field is unknown but probably falls between 10,000 and 50,000 years ago. Air-fall ash from Mount Mazama's cataclysmic eruption nearly 7,000 years ago (Crater Lake) fills cracks and depressions in the lava.
Derrick Cave Lava Tube:19
Near the main vent, much of the lava flowed through a narrow, open gutter and formed a large, sinuous, well-developed lava tube, Derrick Cave.
| Diamond Peak |
Diamond Peak:4
Diamond Peak, the dominant landform in the Willamette Pass area, is a basaltic andesite shield, approximately 15 cubic kilometers in volume. Like other shields in the area, it has a central pyroclastic cone (locally palagonitized but mostly fresh basaltic andesite cinders and glassy scoria) that is surrounded and surmounted by lava flows. Volcaniclastic rocks such as lahars and pyroclastic flows are unknown. Diamond Peak began erupting from a vent near its northern summit. A second vent later opened near the southern summit, piggy-backing its lava and tephra over the previously erupted volcanic rocks. This vent migration likely involved only a small interval of times. Diamond Peak is probalby less than 100,000 years old, but is certainly older than the last glaciation, which ended approximately 11,000 years ago.
| Fort Rock |
Fort Rock Basin:19
Nearly 40 maars, tuff rings, and tuff cones
of Pliocene and Pleistocene age occur in the
Fort Rock Basin of south-central Oregon. Most are significantly eroded, allowing
excellent exposures of their lithology, bedding, and sedimentary structures; a few retain much
of their original morphology. The Fort Rock Basin is dry, internally drained, and largely
filled with lacustrine sediments which accumulated during the episodic existence of pluvial
Fort Rock Lake. This area lies within the extensional environment of the Basin and Range
Province and is characterized by numerous normal faults of Pliocene and Pleistocene age that
cut volcanic rocks of similar age.
Maar volcanoes are low volcanic cones with broad, bowl-shaped crater. Three general kinds are
well-represented in the Fort Rock Basin:
maar, with a crater floor below original
ground level, such as Hole-in-the-Ground;
tuff ring, with a crater floor at or
above original ground level, such as Fort Rock; and
tuff cone, which is a tall
tuff ring, such as Table Rock.
The maar volcanoes of the Fort Rock Basin are the result
of the explosive interaction of rising basaltic magma and abundant surface or groundwater.
Beyond the basin where surface or shallow groundwater was not available, eruptions produced
cinder cones and lava flows.
Fort Rock State Monument - National Natural Landmark:33
49 miles south-southeast of Bend in Lake County. A striking
example of a circular, fort-like volcanic outcrop. Owner: State.
DESIGNATION DATE:
January 1976
| Frog Lake Buttes |
Frog Lake Buttes:4
Frog Lake Buttes near Wapinitia Pass on U.S. Highway 26 are a cluster of dacite domes. They are reversely polarized (thus older than 0.73 million years) but undated by isotopic methods.
| Grassy Mountain |
Grassy Mountain:1
The Owyhee Uplands have been uplifted to more than 4,000 feet above sea level, and the resulting stream erosion has produced the deep, narrow, winding
canyons seen in the area today. The Owyhee volcanic field includes several
calderas, such as at Grassy Mountain and Mahogany Mountain, that are large
collapse features better recognized by the distribution of specific types of
volcanic rocks rather than by present day topography.
| Hole-in-the-Ground |
Fort Rock Basin:19
Nearly 40 maars, tuff rings, and tuff cones
of Pliocene and Pleistocene age occur in the
Fort Rock Basin of south-central Oregon. Most are significantly eroded, allowing
excellent exposures of their lithology, bedding, and sedimentary structures; a few retain much
of their original morphology. The Fort Rock Basin is dry, internally drained, and largely
filled with lacustrine sediments which accumulated during the episodic existence of pluvial
Fort Rock Lake. This area lies within the extensional environment of the Basin and Range
Province and is characterized by numerous normal faults of Pliocene and Pleistocene age that
cut volcanic rocks of similar age.
Maar volcanoes are low volcanic cones with broad, bowl-shaped crater. Three general kinds are
well-represented in the Fort Rock Basin:
maar, with a crater floor below original
ground level, such as Hole-in-the-Ground;
tuff ring, with a crater floor at or
above original ground level, such as Fort Rock; and
tuff cone, which is a tall
tuff ring, such as Table Rock.
The maar volcanoes of the Fort Rock Basin are the result
of the explosive interaction of rising basaltic magma and abundant surface or groundwater.
Beyond the basin where surface or shallow groundwater was not available, eruptions produced
cinder cones and lava flows.
| Harter Mountain |
Harter Mountain:4
Harter Mountain, 5 kilometers northwest of Iron Mountain, is a relatively unknown Quaternary basalt or basaltic andesite shield.
| Iron Mountain |
Iron Mountain:4
Several Pliocene basaltic andesite shields form a ridge just west of the High Cascades, southwest of Mount Jefferson. The best known volcano of this group is Iron Mountain, which towers above U.S. Highway 20 near Tombstone Pass. The cliffs of Iron Mountain expose bedded cinders intruded by dikes and sills.
| John Day Fossil Beds National Monument |
John Day Fossil Beds National Monument:14
Within the heavily eroded volcanic deposits of the
scenic John Day River basin is a well-preserved
fossil record of plants and animals. This
remarkably complete record, spanning more than
40 of the 65 million years of the Cenozoic Era (the
"Age of Mammals and Flowering Plants") is
world-renown. Authorized October 26, 1974, and
established in 1975, this 14,000 acre park is
divided into three widely separated units (separate locations); the Sheep
Rock Unit, Painted Hills Unit, and Clarno Unit.
John Day and Muscall Formations:14,16
The John Day Formation
contains colorful deposits of ash that erupted in the Cascades and carried eastward by
winds. Most of the glass shards that make up the ash layers have turned into clays, zeolites, and opal.
Multiple volcanic events during the deposition of the formation produced
large amounts of volcanic ash. The resulting tuff,
interspersed throughout the fossil-bearing beds,
allows determination of accurate radiometric dates.
The interval between deposition of the John Day (37-20 million years ago) and Mascall (15-12 million years ago)
times was marked by intermittent flows of basaltic lava that
repeatedly leveled and denuded the region. By 15 million years ago,
these eruptions had ceased and the basalt was weathering
into soil. A moderate climate, sufficient precipitation, periodic
deposits of volcanic ash, and the basaltic parent material
combined to produce highly fertile soils, and from these soils arose lush,
nutritious grasses and mixed hardwood forests, much
like those found today in the eastern United States.
| Klamath Mountains |
Klamath Mountains:25
The Klamath Mountains are steep,
rugged mountains consisting of
metamorphic and igneous rocks that
formed in an oceanic setting and
subsequently collided with the
North American continent about 150 million
years ago. Complexly folded and
faulted rocks are bounded by belts of
sparsely vegetated bands of serpentine.
Rocks, including igneous,
metamorphic, and sedimentary types,
are very diverse and interspersed.
The Klamath Mountains were formed,
in part, by the rotation and westward
movement of what was once the northern
Sierra Nevada Mountains. Other
rock types, including limestone and
serpentine, formed under the ocean
floor, were uplifted, and attached to
the continent. Still other rocks formed
from the melting and subsequent uplift
caused by the sinking of the Pacific
plate under the North American plate.
The Klamath Mountains are irregular and
do not form well defined ranges.
Most of the short ranges which do occur
in the Klamath Mountains run
east-west, an unusual characteristic for
mountains in North America.
| Lake Owyhee |
Lake Owyhee:1
Lake Owyhee, created by a dam on the Owyhee River, offers boaters an
extraordinary view of Miocene volcanism (about 15 million years ago). Ash from
that time preserved plant and animal fossils that show a much wetter climate.
Rhinoceroses lived next to ancestral horses, deer and antelope. The off-white
ash layers, pinkish-gray rhyolite, and dark colored basalt create a colorful palette.
The Owyhee Uplands have been uplifted to more than 4,000 feet above sea level, and the resulting stream erosion has produced the deep, narrow, winding
canyons seen in the area today. The Owyhee volcanic field includes several
calderas, such as at Grassy Mountain and Mahogany Mountain, that are large
collapse features better recognized by the distribution of specific types of
volcanic rocks rather than by present day topography.
These same volcanic processes have been responsible for numerous gold
occurrences which have been prospecting targets over the last few years.
Typically, the gold occurs as microscopic particles that have been deposited by
hot-spring systems.
Access: From Interstate I–84 at Ontario south on State Highway 201 toward
Adrian. Several roads branch off toward the west to Lake Owyhee State Park.
| Lava Butte |
Lava Butte:16
About 7,000 years ago, a dozen or so lava flows and cinder cones erupted from fissures on the flanks of Newberry
Volcano. One is Lava Butte, a 500-foot-high cinder cone south of Bend along Highway 97. A
road spirals to the top providing a grand vista of volcanic country. Here, gas-charged molten rock sprayed volcanic
foam (cinders) into the air. These fell back into a pile to form Lava Butte. As the eruption proceeded, the amount of
gas (mostly water vapor) contained in the molten rock decreased and lava poured out the south side of Lava Butte
and flowed 6 miles downhill. The lava spilled into the nearby Deschutes River forming lava dams in some places and
shoving the river westward out of its channel in others.
| Mahogany Mountain |
Mahogany Mountain:1
The Owyhee Uplands have been uplifted to more than 4,000 feet above sea level, and the resulting stream erosion has produced the deep, narrow, winding
canyons seen in the area today. The Owyhee volcanic field includes several
calderas, such as at Grassy Mountain and Mahogany Mountain, that are large
collapse features better recognized by the distribution of specific types of
volcanic rocks rather than by present day topography.
| Mount Bachelor |
Mount Bachelor Volcanic Chain:7
The Mount Bachelor volcanic chain
provides one example of the type and scale of
eruptive activity that has produced most of the High Cascades platform,
which consists chiefly of scoria cones and lava flows, shield volcanoes,
and a few steep-sided cones of basalt and basaltic andesite.
The chain is 25 kilometers long; its lava flows cover 250 square kilometers
and constitute a total volume of 30-50 cubic kilometers.
(Also see Three Sisters below)
| Mount Bailey |
Mount Bailey:4
Mount Bailey is the southernmost volcano in a north-south-trending volcanic chain 10 kilometers long that rises west of Diamond Lake. Bailey is about the same age as Diamond Peak, 43 kilometers north, less than 100,000 years but older than 11,000 years, on the basis of glacial evidence and morphologic comparisons with dated volcanoes. Like Diamond Peak, Bailey consists of a tephra cone surrounded by basaltic andesite lava. Bailey is slightly smaller (8-9 cubic kilometers) than Diamond Peak, and minor andesite erupted from the summit cone in its late stages, whereas Diamond Peak eruptions were never more siliceous than basaltic andesite.
| Mount Hood |
Mount Hood:3,4
For the general public, Mount Hood is perhaps the most accessible and
preeminent of Oregon's volcanoes, located only 75 kilometers east-southeast of
Portland, Oregon. It is the highest peak in the state
(3,426 meters - 11,239 feet) and one of
the most often climbed peaks in the Pacific Northwest.
Mount Hood is one of the major volcanoes of the Cascade Range,
having erupted repeatedly for hundreds of thousands of
years, most recently during two episodes in the past
1,500 years.
Mount Hood Eruptions:18
Mount Hood last erupted about 200 years ago, producing small pyroclastic flows,
lahars, and a prominent
lava dome (Crater Rock) near the volcano's summit.
Most recently, a series of steam blasts occurred between
1856 and 1865.
Cooper Spur:8
Below and east of the summit lies
Cooper Spur, a remnant of the broad
fan of pyroclastic-flow and lahar deposits
of the Polallie eruptive period that originated
from near-summit lava domes.
| Mount Jefferson |
Mount Jefferson:18,24
Mount Jefferson is a prominent feature of the
landscape seen from highways east and west of
the Cascades. Mount Jefferson (one of thirteen
major volcanic centers in the Cascade Range) has
erupted repeatedly for hundreds of thousands of
years.
Mount Jefferson last erupted more than 20,000 years ago.
However, eruptions nearby have produced several
lava flows and small volcanic cones in the past 10,000 years.
| Mount McLoughlin |
Mount McLoughlin:17
Mount McLoughlin rises 1,200 meters as a steep-sided, dominantly
basaltic andesite lava cone above the low Pliocene and Pleistocene basaltic andesite
shields on which it is built. McLoughlin is easily recognized from as far away as
Medicine Lake in California, along I-5 between Yreka, California, and Medford, Oregon,
or around the rim of Crater Lake. Although it is the tallest volcano between Shasta and
Crater Lake, McLoughlin, with a volume of only 13 cubic kilometers, is dwarfed by the
bulk of Shasta (350 cubic kilometers) and Mazama (130 cubic kilometers [Crater Lake]).
Mount McLoughlin is a young volcano. A pronounced magnetic high centered
just east of McLoughlin's main vent is interpreted as
indicating that most of the main cone is normally polarized and thus
less than approximately 700,000 years old. The well preserved shape of
the mountain's west and south flanks, the lack of soil development on many flows,
and preservation of primary flow features suggests that the
bulk of the main cone is no older than 200,000 years, with much of it probably younger.
The main cone was essentially complete before the
last major Pleistocene glaciation. Many flank flows are younger than the main cone;
some may be as young as 20,000 - 30,000 years.
| Mount Tabor |
Mount Tabor:28
Portland's Mount Tabor was named after another Mount Tabor,
which sits six miles east of Nazareth in Israel. Our Mount
Tabor makes Portland one of only two U.S. cities to
have an extinct volcano within its boundaries; the other city
is Bend, Oregon! The volcanic features of Mount Tabor
became known in 1912, years after Mount Tabor became a
public park. The volcanic cinders discovered
in the park were later utilized in surfacing Mount Tabor Park's roads.
Mount Tabor now contains a permanent exhibit
of the volcanic cone from which the cinders were obtained. At the
top of the park is a statue of a former editor of the
Oregonian, Harvey W. Scott.
| Mount Thielsen |
Mount Thielsen:4
Mount Thielsen is a normally polarized shield volcano comprising approximately 8 cubic kilometers of basaltic andesite built atop a broad pedistal (24 cubic kilometers) of older lava. Thielsen is remarkable even at a distance for its colorfully interbedded pyroclastic rocks that dip away from the jagged spire of the central plug, often called the "lightning rod of the Cascades". The most spectacular views are on the north and east sides (accessible only by foot or horseback) where now-vanished glaciers have carved precipitous cirque walls that reveal the construction. Thielsen's age is approximately 290,000 years (whole-rock K-Ar), and its geomorphology is a reference point for assigning Cascade Range volcanoes to the age divisions 0-250,000 years (younger than Thielsen) or 250,000 - 730,000 years (older than Thielsen). Very little of Thielsen's underpinnings are exposed because of Holocene Mazama ash, which erupted from vents at Crater Lake National Park (20 kilometers south), forms a shroud 4 to 20 meters thick in the Thielsen area.
| Mount Washington |
Mount Washington:26
The age of Mount Washington is probably no more than a few 100,000 years,
similar to that of other central High Cascade
stratovolcanoes. During the late Pleistocene, cirques were excavated
into the flanks of the summit cone by valley glaciers which extended
more than 12 kilometers east and west. The is no evidence of
recent reactivation of Mount Washington volcanism, but a series of aligned
small basaltic andesite spatter cones erupted on the northeast
flank approximately 1,330 years ago (carbon-14).
Access to the Mount
Washington Wilderness is restricted to foot trails.
The west and southwest sides of the mountain are crossed by the Skyline Trail, 5
kilometers from a trailhead at Big Lake, near U.S. 20.
The best long-distance viewpoints on main highways are from U.S. 20 near Blue Lake
and from Oregon 242 at Windy Point.
| Multnomah Falls |
Multnomah Falls:27
Plummeting 620 feet from its origins on Larch Mountain,
Multnomah Falls is the
second highest year-round waterfall in the United States.
Nearly two million
visitors a year come to see this ancient waterfall
making it Oregon's number one
public destination.
Fed by underground springs from Larch Mountain,
the flow over the falls varies
usually being highest during winter and spring.
Multnomah Falls offers one of the best places in the Columbia River
Gorge National Scenic Area to study geology exposed by floods. Five
flows of Yakima basalt are visible in the fall's cliff face.
|
Newberry Caldera -
Newberry National Volcanic Monument |
Newberry Volcano:18
Newberry Volcano, a broad shield covering more than 500 square miles,
is capped by Newberry Crater, a large
volcanic depression (caldera) 5 miles across.
Its most recent eruption was about 1,300 years ago.
Newberry Volcano:9
Newberry Volcano, centered about 20 miles southeast of Bend, Oregon, is
among the largest Quaternary volcanoes in thee conterminous United States. It
covers and area in excess of 500 square miles, and lavas from it extend
northward many tens of miles beyond the volcano. The highest point on the
volcano, Paulina Peak with an elevation of 7,984 feet, is about 4,000 feet
higher than the terrain surrounding the volcano. The
gently sloping flanks, embellished by more than 400 cinder cones,
consist of basalt and basaltic andesite flows, andesitic to
rhyolitic ash-flow
and air-fall tuffs and other types of pyroclastic deposits, dacite to rhyolite
domes and flows, and alluvial sediments produced during periods of erosion of
the volcano. At Newberry's summit is a 4- to 5-mile-wide caldera
that contains scenic Paulina and East Lakes.
Big Obsidian Flow:9
Newberry's most recent eruption 1,300 years ago produced the Big Obsidian
Flow.
|
Newberry National Volcanic Monument:16
Within the Newberry National Volcanic Monument,
one finds some of the most unique attractions in the nation.
Cinder cones, pumice cones,
lava flows, including obsidian flows, Lava Cast Forest, caves, lakes, streams, and
waterfalls all attract visitors to this marvelous area.
Newberry Crater - National Natural Landmark:33
Deschutes National Forest, 24 miles southeast of Bend in
Deschutes County. The crater is a basin at the top of a
dormant, though young, volcano which is the largest
Pleistocene volcano east of the Cascade Range. Owner:
Federal.
DESIGNATION DATE:
January 1976
| Owyhee Volcanic Field |
Owyhee Volcanic Field:1
The Owyhee Uplands have been uplifted to more than 4,000 feet above sea level, and the resulting stream erosion has produced the deep, narrow, winding
canyons seen in the area today. The Owyhee volcanic field includes several
calderas, such as at Grassy Mountain and Mahogany Mountain, that are large
collapse features better recognized by the distribution of specific types of
volcanic rocks rather than by present day topography.
| Panorama Point |
Panorama Point:8
The Hood River Valley is an incompletely
understood structural depression extending
north into Washington and southward
toward Mount Hood. The valley's east margin
is a series of anastomosing normal-slip faults
that displace the Columbia River
Basalt Group by about 550 meters in the area
of Panorama Point. Panorama Point itself is a
promontory of the Wanapum
Basalt Formation, but the hills to the east
in the Hood River escarpment are underlain
by the Grande Ronde Basalt, a
stratigraphically lower formation (also in CRBG)
displaced upward by the faults.
The valley extends north a few kilometers
into Washington, although an early Pleistocene volcano,
Underwood Mountain, fills
much of it there.
| Pelican Butte |
Pelican Butte:17
Pelican Butte is a normally polarized, steep-sided andesite shield built on faulted Pliocene and early Pleistocene basaltic andesite. Pleistocene glaciation carved a steep canyon and broad cirque in the northeast flank of the volcano, lowered the summit some tens of meters, and exposed a lava-filled intrusive conduit. However, the volcano's original shape is largely preserved. Pelican Butte (20 cubic kilometers) is volumetrically one of the larger Quaternary volcanoes between Crater Lake and Mount Shasta; it is larger by one-third than the nearby more scenic Mount McLoughlin.
| Peter Skene State Scenic Viewpoint |
Ogden Wayside:2
If you enjoy vertical basalt cliffs and scenic river canyons,
the Ogden Wayside is for you. The park is
perched at the top of a striking canyon. Bring a camera!
U.S. 97, 9 miles north of Redmond, Oregon.
| Pilot Butte State Scenic Viewpoint |
Pilot Butte:2
Come and explore an old cinder cone located
just east of Bend. Hike up and around on one of three
trails. The trails wind through stands of
juniper and sage. All of the trails lead to the summit. Once at
the top, get ready for a grand panoramic
view of the high desert.
To the west at sunset, the glow of snowcapped
Cascade mountains put on a spectacular show.
Three Sisters, Mount Jefferson, Black Butte
and Mount Hood are some of the highlights. Bring something
to quench your thirst after the climb;
there's no drinking water at the park.
| Pilot Rock |
Pilot Rock:25
Pilot Rock, the remnant of an ancient volcano,
stands out as one of the Cascade-Siskiyou National Monument's (BLM)
most striking
features. Visible from much of the Shasta Valley in
northern California, and parts of Oregon's Rogue
Valley, the rock provides viewers with a look at the
inside of a volcano. Over time, the exterior volcano
eroded away, leaving behind the now cooled
magma of the ancient volcano's central vent. Fossil
sites in the vicinity of Pilot Rock contain leaf
impressions and conifer cones that became
embedded in volcanic ash beds 25-35 million years
ago.
| Portland, Oregon |
Portland, Oregon:10
Metropolitan Portland, Oregon, includes most of a Plio-Pleistocene
volcanic field. The Boring Lava
includes at least 32 and possibly 50 cinder cones
and small shield volcanoes
lying within a radius of 21 kilometers (13 miles) of
Kelly Butte, which is 100
kilometers (62 miles) west of Mount Hood
and the High Cascade axis
-- (Web note:
Kelly Butte is approximately 4 miles east of downtown Portland)-- .
Boring Lava vents have been inactive for at
least 300,000 years.
| Powell Butte |
Powell Butte:28
Powell Butte Nature Park is a huge volcanic mound.
On clear days, five mountains can be seen from the park. It
includes over nine miles of trails that are
suitable for mountain-biking, horseback riding, and hiking.
There is a
0.6 mile paved trail which is disabled-accessible.
The park is home to many birds of prey because part of the park
is an open meadow. Also at home here are
raccoons, gray foxes, coyotes, and deer.
| Rock Mesa |
Rock Mesa:30
Rock Mesa is a spectacular obsidian and pumice dome south of the
South Sister volcano. It covers about two square miles, and from
the air looks like nothing more than a gigantic brown-and-gray
cow-patty.
| Saddle Mountain |
Saddle Mountain:31
Saddle Mountain, at 3,283 feet elevation, is one of the highest peaks in
the Coast Range, and affords a magnificent view of the surrounding
mountains and the coast to the west. It is located 10 miles east of
Seaside, and is reached from the Sunset Highway (U.S. 26) a mile east of
Necanicum Junction. A narrow paved road runs eight miles to the north from
the highway to a large parking lot at the base of the mountain. A gentle,
four-mile trail climbs nearly 1,500 feet from the parking lot to the
forest fire lookout on the summit. The Saddle Mountain breccia (a rock
consisting of broken angular fragments cemented together in a fine-grained
matrix) is volcanic. It was produced about 15 million years ago by
thermal shock, when a great lava flow of Columbia River basalt came down
an ancestral valley of the Columbia River (south of its present course)
and entered the Astoria Sea. The still-hot rock, meeting cold water,
caused steam explosions which broke it up into a great pile of basalt
fragments.
| Sand Mountain |
Sand Mountain:26
The Sand Mountain chains of 23 cinder cones and associated lava fields cover 76 square kilometers on the western margin of the central High Cascades of Oregon. Two north-south alignments of 42 distinct vents intersect beneath the largest cone (Sand Mountain, 250 meters high), suggesting that a complex system of dikes and related conduits exists at depth. Eruptive History: two principal episodes approximately 3,800 and 3,000 years ago.
How to get there: U.S. 126 (east from Eugene) follows the west edge of the Sand Mountain lava field while U.S. 20 (east from Albany) and U.S. 22 (east from Salem) cross over the northern part. Access to Sand Mountain cones (summer months only) is via dirt roads from Big Lake enar U.S. 20 at Santiam Pass.
| Sea Lion Caves |
Sea Lion Caves:30
Sea Lion Caves are reputed to be the largest sea-cave in North America,
and is an outstanding example of erosion by waves in basalt.
| Silver Falls State Park |
Silver Falls State Park:1
Silver Falls State Park's (located on Highway 214 east of Salem) 7-mile
hiking trail takes you near or behind 10 waterfalls
which cascade over steep cliffs of Columbia River
basalt that flowed into this area as molten lava
14-16 million years ago. At North Falls,
chimney-like holes in the overhanging rock are tree
molds formed when hot lava flowed around and over
standing trees.
| Sisi Butte |
Sisi Butte:4
Sisi Butte is a prominent, normally polarized basaltic andesite shield volcano near the headwaters of the Clackamas River. The highest point on Sisi Butte, now marked by a U.S. Forest Service lookout, is 200-300 meters west of the central vent. Erosion has stripped away the pyroclastic cone and denuded a shallow, conduit-filling intrusion, so that the surrounding apron of lava now stands slightly higher than the volcano's eruptive center. Glaciers have carved the northeast flank and left moraines strung out to the north and east.
| Siskiyou Mountains |
Siskiyou Mountains:25
The Siskiyou Mountains are one the
east-west running ranges that make up
the Klamath Mountains. Oregon's
oldest known rocks (425 million years
old) are found in the Siskiyou Mountains.
The Siskiyou Crest is a span of
tall peaks beginning in the
vicinity of Pilot Rock and Mount Ashland and
continuing westward and then
south for approximately 70 miles. The soils of
this region are as diverse as
the underlying geology. The rocks vary in
composition from granitics
(igneous rocks) to the metamorphosed
peridotites (serpentine). The
Siskiyou Mountains were not heavily glaciated
in the last ice age and served as a
refuge for species whose habitat
disappeared under tons of continental ice.
| Smith Rock State Park |
Smith Rock:2
Appreciate this Gift from Geologic Wonderland
The dramatic appearance of the park area is a testament
to both the accumulative force of vulcanism
and the erosive power of running water. Geologists
say this area was a major center of volcanic activity
millions of years ago. After a period of localized
eruptions, lava flows entered the canyon and crowded
the ancestral river into the flanks of the main volcanic
structure. Forced to establish a new channel,
the Crooked River eventually eroded the interior of
the volcanic vent. The park's wondrous and multi-colored
formations are composed of rock known as
"welded tuff " - volcanic ash erupted under conditions
of extreme heat and pressure.
| Snow Peak |
Snow Peak:4
Snow Peak is a Pliocene volcanic center 40 kilometers east of Albany, Oregon. Two K-AR ages indicate its age is appromixately 3 million years ago.
| Table Rock (Fort Rock Basin) |
Fort Rock Basin:19
Nearly 40 maars, tuff rings, and tuff cones
of Pliocene and Pleistocene age occur in the
Fort Rock Basin of south-central Oregon. Most are significantly eroded, allowing
excellent exposures of their lithology, bedding, and sedimentary structures; a few retain much
of their original morphology. The Fort Rock Basin is dry, internally drained, and largely
filled with lacustrine sediments which accumulated during the episodic existence of pluvial
Fort Rock Lake. This area lies within the extensional environment of the Basin and Range
Province and is characterized by numerous normal faults of Pliocene and Pleistocene age that
cut volcanic rocks of similar age.
Maar volcanoes are low volcanic cones with broad, bowl-shaped crater. Three general kinds are
well-represented in the Fort Rock Basin:
maar, with a crater floor below original
ground level, such as Hole-in-the-Ground;
tuff ring, with a crater floor at or
above original ground level, such as Fort Rock; and
tuff cone, which is a tall
tuff ring, such as Table Rock.
The maar volcanoes of the Fort Rock Basin are the result
of the explosive interaction of rising basaltic magma and abundant surface or groundwater.
Beyond the basin where surface or shallow groundwater was not available, eruptions produced
cinder cones and lava flows.
| Table Rocks |
Table Rocks:30
The three mesas, located a mile or so apart
in the Rogue River area north of Medford, rise 800 to 1,000 feet above the
valley floor. Their cappings are all parts of a lava flow about 125 feet
thick, which some 3 million years ago traveled down the Rogue River valley
from the High Cascades far to the northeast.
| Three-Fingered Jack |
Three-Fingered Jack4
Three Fingered Jack (2,390 meters) is
a distinctive volcano in
the Central Oregon High Cascades south of Mount Jefferson.
This
deeply glaciated basaltic andesite shield volcano
has around 800 meters of relief and is centered on a pyroclastic cone that
underlies the summit of the mountain. The cone lacks a high-level
conduit-filling plug, however, unlike other shield volcanoes such as nearby
Mount Washington south of Santiam Pass. Three Fingered Jack is undated by
radiometric methods, but its age probably lies between 500,000 and 250,000 years,
as inferred from its erosional state compared to other shield
volcanoes in the High Cascades.
| Three Sisters Region |
Three Sisters Volcanic Center:18
Three Sisters Volcanic Center in central Oregon includes five large volcanoes --
North Sister, Middle
Sister, South Sister, Broken Top, and Mount Bachelor.
South Sister is the youngest volcano in the group; its
most recent eruption was about 2,000 years ago.
Middle Sister and Mount Bachelor have not erupted in the
past 8,000 years, and North Sister and Broken Top
have probably been inactive for 100,000 years.
Composite and Mafic Volcanoes:6
Two types of volcanoes exist in the Three Sisters region and each poses
distinct hazards to people and property. South Sister, Middle Sister, and
Broken Top, major composite volcanoes
clustered near the center of the
region, have erupted repeatedly over tens of thousands of years and may
erupt explosively in the future. In contrast, mafic volcanoes, which range
from small cinder cones to large shield volcanoes like North Sister and
Belknap Crater, are typically short-lived (weeks to centuries) and erupt
less explosively than do composite volcanoes. Hundreds of mafic volcanoes
scattered through the Three Sisters region are part of a much longer zone
along the High Cascades of Oregon in which birth of new mafic volcanoes
is possible.
| Tipsoo Peak |
Tipsoo Peak:4
Tipsoo Peak is a basaltic cinder cone that erupted lava flows, probably within the last 100,000 years.
|
Volcanic Legacy Scenic Byway -
All American Road |
All American Road:22
As its name implies, this roadway has been singled out by the
State of Oregon for its jaw-dropping beauty. The federal
government concurs. In 1999, All American Road status was
awarded this spectacular drive.
Crater Lake National Park, the most dramatic feature of the
Volcanic Legacy Scenic Byway, is just the beginning of the
adventure. Ancient natural chimneys - fumaroles - dominate
the canyon along Annie Creek.
Descending from the mountains, travelers enter the sprawling
Wood River Valley - home to vast herds of cattle. The
remainder of the drive passes through Upper Klamath National
Wildlife Refuge, alongside Upper Klamath Lake and south to
the Oregon/California border.
| Wallowa Mountains |
Wallowa Mountains:1
The rock at the core of the Wallowa
Mountains is the Wallowa batholith, granite from a magma upwelling in
Late Jurassic and Early Cretaceous time (between 160 million and 120
million years ago) that also cemented together a great diversity of still
older, “exotic” terranes—blocks of the Earth’s crust that traversed the
Pacific Ocean and attached themselves to the (then) edge of the North
American continent.
Wallowa Batholith and Columbia River Basalt Feeder Dikes:34
The Wallowa Mountains are largely composed of the Wallowa
batholith, a series of Late Jurassic intrusions
(approximately 140–160 million years ago)
related to the accretion of island-arc terranes onto
the former margin of North America.
The batholith is composed of biotite-and hornblende-bearing tonalite to
granodiorite. During the Miocene,
Columbia River Basalt Group (CRBG) flood basalt was erupted from
vents primarily in northeastern Oregon, with the Wallowa Mountains
hosting over 90 percent of the CRBG dikes in Oregon.
Feeder dikes of both the Imnaha Basalt (approximately 16.8–17.3 million years ago)
and the Grande Ronde Basalt (approximately 15.6–16.8 million years ago) lace the batholith.
Uplift and Pleistocene glaciation have resulted in
exposure of both the Wallowa batholith and the CRBG dikes.
Individual basalt dikes within the Wallowa batholith extend up to several
kilometers along strike, are a
few centimeters to 50 meters wide, are
steeply dipping (average 70 degrees), and
strike generally northwest-southeast.
| Wrights Point |
Wrights Point:30
Wrights Point is a narrow flat-topped tongue of land extending
easterly for 8 miles into the Malheur Valley, 10 miles south of
Burns, Oregon. A quarter- to a half-mile wide, Wrights Point rises
220 to 241 feet above the valley and is capped by a 50-foot cliff
of basalt. The formation slopes to the east about 10 feet per
mile, and if it were isolated, it would be called a mesa. The flow
probably came from a group of craters 5 miles to the west and
pushed down a small channel cut in the alluvial fan. As the
alluvium eroded away and the surface of the Malheur Valley lowered,
the resistant basalt preserved the old channel.
| Youtikut Pillars |
Youtikut Pillars:32
Youtikut is the Chinook jargon word for "long in length".
The Youtikut Pillars is a rock
formation of tilted volcanic columnar basalt,
and weathering has highlighted these columns.
It is located on the southwest side of OK Butte.
Excerpts from:
1) Oregon Department of Geology and Mineral Resources Website, 2001, 2002, 2003
2) Oregon State Parks Website, 2002
3) Scott, et.al., 1997,
Volcano Hazards in the Mount Hood Region, Oregon:
USGS Open-File Report 97-89
4) Sherrod, 1990, IN:
Wood and Kienle, 1990, Volcanoes of North America:
United States and Canada:
Cambridge University Press, 354p.
5) Hoblitt, et.al., 1987;
6) Scott, Iverson, Schilling, and Fischer, 2001;
Volcano Hazards in the Three Sisters Region, Oregon: USGS Open-File
Report 99-437
7) Scott and Gardner, 1990,
Field trip guide to the central Oregon High Cascades,
Part 1: Mount Bachelor-South Sister area: Oregon
Geology, v.52, n.5, September 1990, p.99-101
8) Scott, et.al., 1997, Geologic History of Mount Hood Volcano, Oregon --
A Field-Trip Guidebook: USGS Open-File Report 97-263
9) Sherrod, et.al., 1997, and MacLeod, 1981
10)
Allen, 1990, IN:
Wood and Kienle, 1990, Volcanoes of North America: United States and Canada:
Cambridge University Press, 354p.
11)
U.S. National Park Service Website,
Crater Lake National Park Website, 2000, 2001
12) Wood, 1990, IN: Wood and Kienle, 1990,
Volcanoes of North America: United States and Canada:
Cambridge University Press, 354p.
13) U.S. Army Corps of Engineers, Portland District, and the
U.S. Department of the Interior, U.S. Geological Survey, The
Geologic History of the Columbia River Gorge: Information Brochure
14) U.S. National Park Service Website,
John Day Fossil Beds National Monument, 2001
15) USGS A Tapestry of Time and Terrain Website, 2001
16) U.S. Forest Service Website,
Deschutes and Ochoco National Forests, 2002
17) Smith, 1990, IN: Wood and Kienle, 1990,
Volcanoes of North America: United States and Canada:
Cambridge University Press, 354p.
18) Dzurisin, et.al., 1997,
Living With Volcanic Risk in the Cascades: USGS Fact Sheet 165-97
19) Chitwood, 1990, IN:
Wood and Kienle, 1990, Volcanoes of North America: United States and Canada:
Cambridge University Press, 354p.,
20) USGS/NPS Geology in the Parks Website, 2001
21) Gemstones, An Overview of Production of Specific U.S. Gemstones:
U.S. Bureau of Mines Special Publication 14-95
22) Klamath County Tourism Website, 2002
23) R.L. Whitehead, 1994, Ground Water Atlas of the United States:
Idaho, Oregon, Washington:
U.S. Geological Survey HA730-H
24) Walder, et.al., 1999;
25) U.S. Bureau of Land Management,
Cascade-Siskiyou National Monument Website, 2002
26) Taylor, 1990, IN:
Wood and Kienle, 1990, Volcanoes of North America: United States and Canada:
Cambridge University Press, 354p.
27) U.S. Forest Service Website, 2002,
Pacific Northwest Region,
Columbia Gorge National Scenic Area
28) City of Portland Parks and Recreation Website, 2002
29) Columbia Basin Fish and Wildlife Authority Website, 2002
30) Allen, 1987, Time Travel in Oregon,
a scrapbook of geological articles published in
'The Oregonian' from November 3, 1983 to October 31, 1985
31) Allen, 1987, Time Travel Two in Oregon, a scrapbook of geological
articles published in 'The Oregonian' from November 7, 1985 to November 6,
1987
32) U.S. Forest Service Website,
Umpqua National Forest, 2003
33) U.S. National Park Service,
National Natural Landmarks Website, 2003
34) Petcovic and Gunder, 2001, Partial melting of tonalite at the margins of a Columbia River Basalt Group dike, Wallowa Mountains, northeastern Oregon IN: Oregon Geology, July 2001
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