Newberry Volcano
Encyclopedia
Newberry Volcano is a large potentially active shield volcano
located 40 miles (64.4 km) east of the Cascade Range
and about 20 miles (32.2 km) southeast of Bend, Oregon
. It is not a typical shield volcano. In addition to erupting basalt
ic lavas, it also has erupted andesitic
and even rhyolitic
lava.
The volcano
is 20 miles (32 km) in diameter and has an approximate volume of 80 cubic miles (333.5 km³). It possesses a large oval-shaped caldera
4 xx in diameter, called the Newberry Caldera. Within the caldera there are two lakes (Paulina Lake
and East Lake
), many pyroclastic cones, lava flows, and obsidian
domes.
A deep gash in the northern caldera wall, dubbed "The Fissure", is the end of a 29 miles (46.7 km) long series of fractures called the Northwest Rift Zone
. Approximately 6,100 years ago, fissure basalt flows erupted from the rift and covered part of Newberry's northwest flank.
Newberry Volcano was named for John Strong Newberry
, who explored central Oregon for the Pacific Railroad
Surveys in 1855.
During the Apollo program, parts of the volcano that resemble the Moon
's surface were used to train the astronaut
s.
, and the High Lava Plains (area of blue lines on diagram at right) of volcanic features in central Oregon that have been developing since about 16 Ma. Volcanism in the High Lava Plains is bimodal, having both basaltic (mafic) and rhyolitic (silicic) types of lava. Some of the rhyolites show a progression in ages from about 10 Ma in the east to the geologically recent Newberry Caldera in the west. This track, and its implication of a moving source, roughly mirrors the similar track of the Yellowstone Hotspot
from the McDermitt Caldera on the Oregon—Nevada border, on which basis the Newberry volcanism has been attributed to a so-called hotspot
(a plume of hot material arising from the earth's mantle). But whereas the Yellowstone Hotspot reflects the motion of the North American plate
across a hotspot, the Newberry track does not. Although the cause of the intense regional volcanism around 16 Ma is hotly debated, the age progression across the High Lava Plains is now attributed to a reservoir of hot material that expanded over time, and the linearity of the trend attributed to exploitation of a deep, pre-existing weakness in the crust associated with the Brothers Fault Zone
.
A great deal of volcanic activity has occurred on Newberry's shield, which itself has one of the largest collections of cinder cone
s, domes, lava flows, and fissures
in the world—so much so that local residents call these parasitic vents the "Paulina Mountains", thinking of them as a separate mountain range
. Most of the cinder cones are 200 foot high and have shallow saucer-shaped summit craters. They are typically surrounded by basalt or andesite that erupted from their bases forming large lava
beds. The northern flank holds three distinct lava tube
systems that formed in pāhoehoe: the Horse Lava Tube System
, Arnold Lava Tube System
, and the Lava Top Butte basalt. On the northwest flank of the volcano is Lava Butte
, located next to Highway 97
south of Bend, is a good example of this kind of cinder cone and an [[ʻAʻā|aā]] lava bed. There are also about 20 rhyolite domes or fissures on the eastern, southern, and western flanks. Larger examples include 580,000-year-old McKay Butte on the west flank, 80,000-year-old China Hat and 850,000-year-old East Butte on the far eastern base.
During the late Pleistocene
and Holocene
periods, there have been six eruptive episodes. Four of them rhyolitic
, on the eastern half of the caldera, and two basalt
ic, on the flanks.
Newberry's highest point is located 1500 foot above the southern caldera floor on Paulina Peak, which is just one peak on the caldera rim. The volcano's south flank descends into the basaltic flatlands of central Oregon.
Newberry Caldera has existed possibly as long as 500,000 years, when the cone of the volcano is thought to have first collapsed. Subsequent caldera-forming collapse events have further deepened the caldera but volcanic material and lake-bed sediment
s have largely filled in much of this depth.
Within the caldera, there are two lakes (Paulina Lake and East Lake), many cinder cones, lava flows, and obsidian domes. The land area of the caldera is often heavily forest
ed, except in areas where there are more recent volcanic flows and features. Paulina Lake is drained by Paulina Creek, which passes through a narrow gorge through the western part of the caldera rim. East Lake does not have a known outlet and is 40 feet (12 m) higher than Paulina Lake. 6700-year-old basalt
flows separate the two caldera lakes. Rising 700 foot above this flow is the Central Pumice Cone.
Both lakes have hot spring
s, and drilling in 1981 found that temperatures in the caldera reach 280 °C (536 °F) at 3057 feet (932 m) below the caldera floor. This is the highest temperature ever recorded at a dormant Cascade volcano, hotter than even The Geysers
of California, the world's largest producer of geothermal power
.
Newberry has had a caldera for possibly as long as 500,000 years, when a large Plinian Eruption
sent so much pyroclastic material gushing from its vent that the then-emptied magma chamber
collapsed. This was repeated for several eruptions; each forming a slightly smaller caldera. The half-million-year-old (estimated) Teepee Draw tuff covers much of the volcano's shield and was from an eruption with an estimated volume of 10 cubic miles (42 km³). This is thought to be the first in a series of caldera-forming eruptions that issued from Newberry's main vent system. One of the later layers is cut by Newberry's only stream, Paulina Creek.
Subsidence of the caldera through time has been partly offset by the deposition of tephra
, lava flows, and lake sediment. The USGS has drilled 3057 feet (931.8 m) below the present surface of the caldera and has found that:
There are several large flows of obsidian in the caldera, one of which, Big Obsidian Flow, was created around 1400 years ago and is thus the most recent caldera eruption. This particular flow erupted from a vent or fissure near the southern wall of the caldera and partially engulfed the Lost Lake pumice ring.
Shield volcano
A shield volcano is a type of volcano usually built almost entirely of fluid lava flows. They are named for their large size and low profile, resembling a warrior's shield. This is caused by the highly fluid lava they erupt, which travels farther than lava erupted from more explosive volcanoes...
located 40 miles (64.4 km) east of the Cascade Range
Cascade Range
The Cascade Range is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, and the notable volcanoes known as the High Cascades...
and about 20 miles (32.2 km) southeast of Bend, Oregon
Bend, Oregon
Bend is a city in and the county seat of Deschutes County, Oregon, United States, and the principal city of the Bend, Oregon Metropolitan Statistical Area. Bend is Central Oregon's largest city, and, despite its modest size, is the de facto metropolis of the region, owing to the low population...
. It is not a typical shield volcano. In addition to erupting basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
ic lavas, it also has erupted andesitic
Andesite
Andesite is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. In a general sense, it is the intermediate type between basalt and dacite. The mineral assemblage is typically dominated by plagioclase plus pyroxene and/or hornblende. Magnetite,...
and even rhyolitic
Rhyolite
This page is about a volcanic rock. For the ghost town see Rhyolite, Nevada, and for the satellite system, see Rhyolite/Aquacade.Rhyolite is an igneous, volcanic rock, of felsic composition . It may have any texture from glassy to aphanitic to porphyritic...
lava.
The volcano
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...
is 20 miles (32 km) in diameter and has an approximate volume of 80 cubic miles (333.5 km³). It possesses a large oval-shaped caldera
Caldera
A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...
4 xx in diameter, called the Newberry Caldera. Within the caldera there are two lakes (Paulina Lake
Paulina Lake
Paulina Lake is one of the twin crater lakes , located above sea level in Newberry Crater, Central Oregon, United States. It is in the Deschutes National Forest near La Pine. The crater was built from 500,000 years of volcanic eruptions. The lake's main inflow is from snow melt, hot springs, and...
and East Lake
East Lake
East Lake is one of the twin lakes that occupy part of the Newberry Crater or caldera in Central Oregon, United States. It is located in the Deschutes National Forest near the city of La Pine. The caldera was formed over 500,000 years ago from volcanic eruptions. East Lake's water comes from snow...
), many pyroclastic cones, lava flows, and obsidian
Obsidian
Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock.It is produced when felsic lava extruded from a volcano cools rapidly with minimum crystal growth...
domes.
A deep gash in the northern caldera wall, dubbed "The Fissure", is the end of a 29 miles (46.7 km) long series of fractures called the Northwest Rift Zone
Rift zone
A rift zone is a feature of some volcanoes, especially the shield volcanoes of Hawaii, in which a linear series of fissures in the volcanic edifice allows lava to be erupted from the volcano's flank instead of from its summit...
. Approximately 6,100 years ago, fissure basalt flows erupted from the rift and covered part of Newberry's northwest flank.
Newberry Volcano was named for John Strong Newberry
John Strong Newberry
John Strong Newberry was a American geologist, physician, explorer, author, and a member of the Megatherium Club at the Smithsonian Institution in Washington, D.C....
, who explored central Oregon for the Pacific Railroad
Pacific Railroad
The Pacific Railroad was a railroad based in the U.S. state of Missouri. It was a predecessor of both the Missouri Pacific Railroad and St. Louis-San Francisco Railway.The Pacific was chartered by Missouri in 1849 to extend "from St...
Surveys in 1855.
During the Apollo program, parts of the volcano that resemble the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
's surface were used to train the astronaut
Astronaut
An astronaut or cosmonaut is a person trained by a human spaceflight program to command, pilot, or serve as a crew member of a spacecraft....
s.
Geology
The Newberry Volcano lies at the northwest end of both the Brothers Fault ZoneBrothers Fault Zone
The Brothers Fault Zone — believed to have been named after Brothers, Oregon — is the most notable of a set of northwest trending fault zones including the Eugene—Denio, McLouglin, and Vale zones that dominate the geological structure of most of Oregon...
, and the High Lava Plains (area of blue lines on diagram at right) of volcanic features in central Oregon that have been developing since about 16 Ma. Volcanism in the High Lava Plains is bimodal, having both basaltic (mafic) and rhyolitic (silicic) types of lava. Some of the rhyolites show a progression in ages from about 10 Ma in the east to the geologically recent Newberry Caldera in the west. This track, and its implication of a moving source, roughly mirrors the similar track of the Yellowstone Hotspot
Yellowstone hotspot
The Yellowstone hotspot, also referred to as the Snake River Plain-Yellowstone hotspot, is a volcanic hotspot responsible for large scale volcanism in Oregon, Nevada, Idaho, and Wyoming, United States. It created the eastern Snake River Plain through a succession of caldera forming eruptions...
from the McDermitt Caldera on the Oregon—Nevada border, on which basis the Newberry volcanism has been attributed to a so-called hotspot
Hotspot (geology)
The places known as hotspots or hot spots in geology are volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the mantle elsewhere. They may be on, near to, or far from tectonic plate boundaries. There are two hypotheses to explain them...
(a plume of hot material arising from the earth's mantle). But whereas the Yellowstone Hotspot reflects the motion of the North American plate
North American Plate
The North American Plate is a tectonic plate covering most of North America, Greenland, Cuba, Bahamas, and parts of Siberia, Japan and Iceland. It extends eastward to the Mid-Atlantic Ridge and westward to the Chersky Range in eastern Siberia. The plate includes both continental and oceanic crust...
across a hotspot, the Newberry track does not. Although the cause of the intense regional volcanism around 16 Ma is hotly debated, the age progression across the High Lava Plains is now attributed to a reservoir of hot material that expanded over time, and the linearity of the trend attributed to exploitation of a deep, pre-existing weakness in the crust associated with the Brothers Fault Zone
Brothers Fault Zone
The Brothers Fault Zone — believed to have been named after Brothers, Oregon — is the most notable of a set of northwest trending fault zones including the Eugene—Denio, McLouglin, and Vale zones that dominate the geological structure of most of Oregon...
.
A great deal of volcanic activity has occurred on Newberry's shield, which itself has one of the largest collections of cinder cone
Cinder cone
According to the , Cinder Cone is the proper name of 1 cinder cone in Canada and 7 cinder cones in the United States:In Canada: Cinder Cone In the United States:...
s, domes, lava flows, and fissures
Fissure vent
A fissure vent, also known as a volcanic fissure or simply fissure, is a linear volcanic vent through which lava erupts, usually without any explosive activity. The vent is usually a few meters wide and may be many kilometers long. Fissure vents can cause large flood basalts and lava channels...
in the world—so much so that local residents call these parasitic vents the "Paulina Mountains", thinking of them as a separate mountain range
Mountain range
A mountain range is a single, large mass consisting of a succession of mountains or narrowly spaced mountain ridges, with or without peaks, closely related in position, direction, formation, and age; a component part of a mountain system or of a mountain chain...
. Most of the cinder cones are 200 foot high and have shallow saucer-shaped summit craters. They are typically surrounded by basalt or andesite that erupted from their bases forming large lava
Lava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...
beds. The northern flank holds three distinct lava tube
Lava tube
Lava tubes are natural conduits through which lava travels beneath the surface of a lava flow, expelled by a volcano during an eruption. They can be actively draining lava from a source, or can be extinct, meaning the lava flow has ceased and the rock has cooled and left a long, cave-like...
systems that formed in pāhoehoe: the Horse Lava Tube System
Horse Lava Tube System
The Horse Lava Tube System is a series of lava tubes within Deschutes County, Oregon, of the United States. The system starts within the Deschutes National Forest on the northern flank of Newberry Volcano and heads north into and near the city of Bend...
, Arnold Lava Tube System
Arnold Lava Tube System
The Arnold Lava Tube System is series of lava tubes within Deschutes County, Oregon, of the United States. It is located several miles southeast of the city of Bend. The system starts within the Deschutes National Forest on the northern flank of Newberry Volcano, heads northeast onto BLM land...
, and the Lava Top Butte basalt. On the northwest flank of the volcano is Lava Butte
Lava Butte
Lava Butte is a cinder cone located in central Oregon, USA, just west of US Highway 97 between the towns of Bend, Oregon, and Sunriver, Oregon. It is part of a system of small cinder cones on the northwest flank of Newberry Volcano, a massive shield volcano which rises to the southeast...
, located next to Highway 97
U.S. Route 97 in Oregon
In the U.S. state of Oregon, U.S. Route 97 is a major north–south United States highway which runs through the state of Oregon . In Oregon, it runs from the Oregon-California border, south of Klamath Falls, to the Oregon-Washington border on the Columbia River, between Biggs Junction, Oregon and...
south of Bend, is a good example of this kind of cinder cone and an [[ʻAʻā|aā]] lava bed. There are also about 20 rhyolite domes or fissures on the eastern, southern, and western flanks. Larger examples include 580,000-year-old McKay Butte on the west flank, 80,000-year-old China Hat and 850,000-year-old East Butte on the far eastern base.
During the late Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
and Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
periods, there have been six eruptive episodes. Four of them rhyolitic
Rhyolite
This page is about a volcanic rock. For the ghost town see Rhyolite, Nevada, and for the satellite system, see Rhyolite/Aquacade.Rhyolite is an igneous, volcanic rock, of felsic composition . It may have any texture from glassy to aphanitic to porphyritic...
, on the eastern half of the caldera, and two basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
ic, on the flanks.
- South Obsidian Eruptive Episode: An estimated 12,000 years ago, an obsidianObsidianObsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock.It is produced when felsic lava extruded from a volcano cools rapidly with minimum crystal growth...
dome and related obsidian flow erupted in the southeast part of the caldera. - East Rim Eruptive Episode: About 11,200 years ago (10,000 14C years B.P.Radiocarbon datingRadiocarbon dating is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" ,...
), maficMaficMafic is an adjective describing a silicate mineral or rock that is rich in magnesium and iron; the term is a portmanteau of the words "magnesium" and "ferric". Most mafic minerals are dark in color and the relative density is greater than 3. Common rock-forming mafic minerals include olivine,...
cinderCinderA cinder is a pyroclastic material. Cinders are extrusive igneous rocks. Cinders are similar to pumice, which has so many cavities and is such low-density that it can float on water...
s, scoriaScoriaScoria is a volcanic rock containing many holes or vesicles. It is most generally dark in color , and basaltic or andesitic in composition. Scoria is relatively low in mass as a result of its numerous macroscopic ellipsoidal vesicles, but in contrast to pumice, all scoria has a specific gravity...
, spatter, and lavaLavaLava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...
flows erupted from a fissure on the east rim of the caldera. - Interlake Eruptive Episode: A series of rhyolitic eruptions began in the caldera approximately 7,300 years ago (6,200 14C years B.P.). They produced a widespread phreatomagmatic pumiceous tephra deposit, obsidian flows, large and small pumice cones, and a pumice ring. This eruptive episode probably lasted for about 200 years.
- Northwest Rift Eruptive Episode: About 7,000 years ago (6,100 14C years B.P.), basaltic andesiteBasaltic andesiteBasaltic andesite is a black volcanic rock containing about 55% silica. Minerals in basaltic andesite include olivine, augite and plagioclase. Basaltic andesite can be found in volcanoes around the world, including in Central America and the Andes of South America. Basaltic andesite is common in...
lava and cinder cones erupted from extensive fissure vents on the northwest and south flanks of Newberry. Spatter and cinders also erupted from a fissure on the north caldera wall. The lava flows range up to 5.6 miles (9 km) long and are more voluminous at lower elevations. This eruptive episode probably lasted for less than 50 years. - East Lake Eruptive Episode: About 3,500 years ago, obsidian flows and associated pumice deposits in the caldera erupted from caldera ring fractures.
- Big Obsidian Eruptive Episode: About 480 A.D. (1,470 14C years B.P.), a three-part sequence of rhyolitic eruptions began which included an air-fall tephraTephra200px|thumb|right|Tephra horizons in south-central [[Iceland]]. The thick and light coloured layer at center of the photo is [[rhyolitic]] tephra from [[Hekla]]....
, ash-flow tephra, and an obsidian flow from a common vent at the base of the south caldera wall. The initial Plinian eruptionPlinian eruptionPlinian eruptions, also known as 'Vesuvian eruptions', are volcanic eruptions marked by their similarity to the eruption of Mount Vesuvius in AD 79 ....
480 A.D. (1,580 14C years B.P.) produced the Newberry pumice fall deposit which blanketed the east flank of the volcano and areas to the east. About 210 years later, the Paulina Lake ash flow (1,310 14C years B.P.) spread from near the south caldera wall to Paulina Lake. The final phase of the eruption produced the Big Obsidian Flow, which covers 1.1 square miles (2.8 km²).
Newberry's highest point is located 1500 foot above the southern caldera floor on Paulina Peak, which is just one peak on the caldera rim. The volcano's south flank descends into the basaltic flatlands of central Oregon.
Caldera
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
s have largely filled in much of this depth.
Within the caldera, there are two lakes (Paulina Lake and East Lake), many cinder cones, lava flows, and obsidian domes. The land area of the caldera is often heavily forest
Forest
A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...
ed, except in areas where there are more recent volcanic flows and features. Paulina Lake is drained by Paulina Creek, which passes through a narrow gorge through the western part of the caldera rim. East Lake does not have a known outlet and is 40 feet (12 m) higher than Paulina Lake. 6700-year-old basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
flows separate the two caldera lakes. Rising 700 foot above this flow is the Central Pumice Cone.
Both lakes have hot spring
Hot spring
A hot spring is a spring that is produced by the emergence of geothermally heated groundwater from the Earth's crust. There are geothermal hot springs in many locations all over the crust of the earth.-Definitions:...
s, and drilling in 1981 found that temperatures in the caldera reach 280 °C (536 °F) at 3057 feet (932 m) below the caldera floor. This is the highest temperature ever recorded at a dormant Cascade volcano, hotter than even The Geysers
The Geysers
The Geysers is a complex of 22 geothermal power plants, drawing steam from more than 350 wells, located in the Mayacamas Mountains north of San Francisco, California.The largest in the world, the Geysers has...
of California, the world's largest producer of geothermal power
Geothermal power
Geothermal energy is thermal energy generated and stored in the Earth. Thermal energy is the energy that determines the temperature of matter. Earth's geothermal energy originates from the original formation of the planet and from radioactive decay of minerals...
.
Newberry has had a caldera for possibly as long as 500,000 years, when a large Plinian Eruption
Plinian eruption
Plinian eruptions, also known as 'Vesuvian eruptions', are volcanic eruptions marked by their similarity to the eruption of Mount Vesuvius in AD 79 ....
sent so much pyroclastic material gushing from its vent that the then-emptied magma chamber
Magma chamber
A magma chamber is a large underground pool of molten rock found beneath the surface of the Earth. The molten rock in such a chamber is under great pressure, and given enough time, that pressure can gradually fracture the rock around it creating outlets for the magma...
collapsed. This was repeated for several eruptions; each forming a slightly smaller caldera. The half-million-year-old (estimated) Teepee Draw tuff covers much of the volcano's shield and was from an eruption with an estimated volume of 10 cubic miles (42 km³). This is thought to be the first in a series of caldera-forming eruptions that issued from Newberry's main vent system. One of the later layers is cut by Newberry's only stream, Paulina Creek.
Subsidence of the caldera through time has been partly offset by the deposition of tephra
Tephra
200px|thumb|right|Tephra horizons in south-central [[Iceland]]. The thick and light coloured layer at center of the photo is [[rhyolitic]] tephra from [[Hekla]]....
, lava flows, and lake sediment. The USGS has drilled 3057 feet (931.8 m) below the present surface of the caldera and has found that:
- First 950 foot: Dominated by air-fall pumicePumicePumice is a textural term for a volcanic rock that is a solidified frothy lava typically created when super-heated, highly pressurized rock is violently ejected from a volcano. It can be formed when lava and water are mixed. This unusual formation is due to the simultaneous actions of rapid...
, obsidianObsidianObsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock.It is produced when felsic lava extruded from a volcano cools rapidly with minimum crystal growth...
flows, and under-water erupted ashVolcanic ashVolcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...
.: Lake-bottom sediments.: Thick layers of pumice-rich ash and brecciaBrecciaBreccia is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix, that can be either similar to or different from the composition of the fragments....
.: RhyoliticRhyoliteThis page is about a volcanic rock. For the ghost town see Rhyolite, Nevada, and for the satellite system, see Rhyolite/Aquacade.Rhyolite is an igneous, volcanic rock, of felsic composition . It may have any texture from glassy to aphanitic to porphyritic...
to daciticDaciteDacite is an igneous, volcanic rock. It has an aphanitic to porphyritic texture and is intermediate in composition between andesite and rhyolite. The relative proportions of feldspars and quartz in dacite, and in many other volcanic rocks, are illustrated in the QAPF diagram...
lava flows.: BasaltBasaltBasalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
to basaltic-andesiteAndesiteAndesite is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. In a general sense, it is the intermediate type between basalt and dacite. The mineral assemblage is typically dominated by plagioclase plus pyroxene and/or hornblende. Magnetite,...
lava flows and breccia.
There are several large flows of obsidian in the caldera, one of which, Big Obsidian Flow, was created around 1400 years ago and is thus the most recent caldera eruption. This particular flow erupted from a vent or fissure near the southern wall of the caldera and partially engulfed the Lost Lake pumice ring.
See also
- Newberry National Volcanic MonumentNewberry National Volcanic MonumentNewberry National Volcanic Monument was designated on November 5, 1990, to protect the area around the Newberry Volcano in the United States. It was created within the boundaries of the Deschutes National Forest and is managed by the U.S. Forest Service...
- Cascade VolcanoesCascade VolcanoesThe Cascade Volcanoes are a number of volcanoes in a volcanic arc in western North America, extending from southwestern British Columbia through Washington and Oregon to Northern California, a distance of well over 700 mi ...
- Brothers Fault ZoneBrothers Fault ZoneThe Brothers Fault Zone — believed to have been named after Brothers, Oregon — is the most notable of a set of northwest trending fault zones including the Eugene—Denio, McLouglin, and Vale zones that dominate the geological structure of most of Oregon...