Mount Washington is a deeply eroded

volcano A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates ...

in the Cascade Range of

Oregon Oregon () is a state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington, while the Snake River delineates much of its eastern boundary with Idah ...

. It lies within Deschutes and Linn counties and is surrounded by the Mount Washington Wilderness area. Like the rest of the Oregon Cascades, Mount Washington was produced by the

subduction Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, ...

of the oceanic Juan de Fuca tectonic plate under the continental North American tectonic plate, forming during the late

Pleistocene The Pleistocene ( , often referred to as the '' Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed ...

. Made mostly of

mafic A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks includ ...

(rich in magnesium and iron) volcanic rock like subalkaline

basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% of a ...

and

basaltic andesite Basaltic andesite is a volcanic rock that is intermediate in composition between basalt and andesite. It is composed predominantly of augite and plagioclase. Basaltic andesite can be found in volcanoes around the world, including in Central Ameri ...

, it has a

volcanic plug A volcanic plug, also called a volcanic neck or lava neck, is a volcanic object created when magma hardens within a vent on an active volcano. When present, a plug can cause an extreme build-up of high gas pressure if rising volatile-charged m ...

occupying its summit cone and numerous dikes. It is surrounded by other volcanic features such as

cinder cone A cinder cone (or scoria cone) is a steep conical hill A conical hill (also cone or conical mountain) is a landform with a distinctly conical shape. It is usually isolated or rises above other surrounding foothills, and is often of volcanic ...

s and

spatter cone Volcanic cones are among the simplest volcanic landforms. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and ...

s. The volcano's last eruptions took place from spatter cones about 1,350 years ago, generating basaltic andesite lava deposits. Mount Washington has barren surroundings, which have seen little historical recreational use. A wagon road at McKenzie Pass was built in 1872, which was later paved during the 1930s. On August 26, 1923, the mountain was first ascended by six boys from the neighboring city of Bend. The surrounding area was designated the Mount Washington Wilderness by the federal government in 1964. The wilderness area is not heavily used, though it has a number of hiking trails. Wildlife is sparse in the region. Vegetation is mostly limited to pines and shrubs. Animal life includes deer, American black bear, cougar, various small animal species, and some fish species in the lakes.

Geography

With an elevation of above sea level, Mount Washington is located in Deschutes and Linn counties in the U.S. state of

. It lies north of McKenzie Pass, and some west of the city of Sisters. It is accessible by foot trails only; the western and southwestern sides of Washington intersect with the Skyline Trail about from the Big Lake trailhead near U.S. Route 20. Despite being one of the smaller volcanic peaks in the Oregon Cascades, Mount Washington is the most prominent landmark between North Sister and Three Fingered Jack, with the Cache Mountain cinder cones to the northeast and Hayrick Butte and Hoodoo Butte to the northwest. The volcano forms a crest of steep, icy mountains with North Cinder Peak and Three Fingered Jack to the south of Mount Jefferson. The volcano has a pinnacle appearance resembling the spire-like shape of Mount Thielsen. According to Harris (2005), the volcano resembles

Cleopatra's Needle Cleopatra's Needles are a separated pair of ancient Egyptian obelisks now in London and New York City. The obelisks were originally made in Heliopolis (modern Cairo) during the New Kingdom period, inscribed by the 18th dynasty pharaoh Thutmose I ...

from certain angles and the

Sugarloaf Mountain Sugarloaf Mountain ( pt, Pão de Açúcar, ) is a peak situated in Rio de Janeiro, Brazil, at the mouth of Guanabara Bay on a peninsula that juts out into the Atlantic Ocean. Rising above the harbor, the peak is named for its resemblance t ...

in Brazil from others. The proximal relief for the volcano is , while the draping relief is . The volcano has an overall volume of .

Physical geography

Elevations in the Mount Washington area range from to greater than . Most precipitation falls during the winter as snow, and summers are warm and dry. During the winter season, the Cascades are covered with thick snow. As a result,

Oregon Route 242 Oregon Route 242, known as a portion of the McKenzie Highway, is an Oregon state highway that runs from Belknap Springs, Oregon through McKenzie Pass in the Oregon Cascades, to Sisters, Oregon, in the United States. The McKenzie Highway was ad ...

over McKenzie Pass becomes impassable from fall through late spring, while the

Santiam Highway U.S. Route 20 (US 20) is a major west–east cross-state highway in the northern part of the U.S. state of Oregon, especially east of the Cascade Mountains. It connects U.S. Route 101 in Newport on the central Oregon Coast to the Idaho ...

and

Oregon Route 126 Oregon OR 126 (OR 126) is a state highway that connects coastal, western, and central parts of the U.S. state of Oregon. A short freeway section of OR 126 in Eugene and Springfield is concurrent with Interstate 105 (I-105). Rou ...

are maintained and remain open. Within the Mount Washington Wilderness, there are

outwash plain An outwash plain, also called a sandur (plural: ''sandurs''), sandr or sandar, is a plain formed of glaciofluvial deposits due to meltwater outwash at the terminus of a glacier. As it flows, the glacier grinds the underlying rock surface and ...

s and lateral, recessional, and terminal ground

moraine A moraine is any accumulation of unconsolidated debris ( regolith and rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a glacier or ice sh ...

s. Many of these glacial deposits were created during the most recent

glacial advance Glacial motion is the motion of glaciers, which can be likened to rivers of ice. It has played an important role in sculpting many landscapes. Most lakes in the world occupy basins scoured out by glaciers. Glacial motion can be fast (up to , o ...

in the late

, though there are

Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...

glacial deposits as well. There was an

ice sheet In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are in Antarctica and Greenland; during the Last Glacial Period at ...

during the late Pleistocene between Mount Washington and Three Fingered Jack. The McKenzie River, fed by Clear Lake, runs south for about just west of Mount Washington before it turns west for another and meets the

Willamette River The Willamette River ( ) is a major tributary of the Columbia River, accounting for 12 to 15 percent of the Columbia's flow. The Willamette's main stem is long, lying entirely in northwestern Oregon in the United States. Flowing northward ...

near the city of

Eugene Eugene may refer to: People and fictional characters * Eugene (given name), including a list of people and fictional characters with the given name * Eugene (actress) (born 1981), Kim Yoo-jin, South Korean actress and former member of the sin ...

Wilderness

The Mount Washington Wilderness covers an area of . First named a wild area by the

United States Forest Service The United States Forest Service (USFS) is an agency of the U.S. Department of Agriculture that administers the nation's 154 national forests and 20 national grasslands. The Forest Service manages of land. Major divisions of the agency inc ...

in 1975, it was designated as one of the original wilderness areas under the 1964

Wilderness Act The Wilderness Act of 1964 () was written by Howard Zahniser of The Wilderness Society. It created the legal definition of wilderness in the United States, and protected 9.1 million acres (37,000 km²) of federal land. The result of a lo ...

. Located to the west of Bend, the Mount Washington plot is the smallest of three wilderness areas that encompass most of the High Cascades, a physiographic region located in the central part of Oregon; the two others are the

Three Sisters Wilderness The Three Sisters Wilderness is a wilderness area in the Cascade Range, within the Willamette and Deschutes National Forests in Oregon, United States. It comprises , making it the second largest wilderness area in Oregon, after the Eagle Cap Wilde ...

and

Mount Jefferson Wilderness The Mount Jefferson Wilderness is a wilderness area located on and around Mount Jefferson in the central Cascade Range of Oregon in the United States. The wilderness lies within the Willamette National Forest and Deschutes National Forest. The ...

. Used mostly by hunters, hikers, and climbers, the Mount Washington area includes the Dee Wright Observatory, smaller volcanoes, and parts of the

Pacific Crest Trail The Pacific Crest Trail (PCT), officially designated as the Pacific Crest National Scenic Trail, is a long-distance hiking and equestrian trail closely aligned with the highest portion of the Cascade and Sierra Nevada mountain ranges, which lie ...

, which runs north–south through the wilderness for about . Other major features include Belknap Crater and 28 lakes. The wilderness area is jointly administered by authorities for the

Willamette National Forest The Willamette National Forest is a National Forest located in the central portion of the Cascade Range of the U.S. state of Oregon. It comprises . Over 380,000 acres (694 mi2, 1,540 km2) are designated wilderness which include seven ...

and

Deschutes National Forest The Deschutes National Forest is a United States National Forest located in parts of Deschutes, Klamath, Lake, and Jefferson counties in central Oregon. It comprises along the east side of the Cascade Range. In 1908, the Deschutes National ...

Mineral and geothermal potential

A mineral survey from 1980 through 1981 detected little potential for metallic mineral or fossil fuel resources in the Mount Washington Wilderness. The area contains large amounts of cinder – more than – but there are alternate sources in the region, which are sufficient to meet local demands. Likewise, there are no mines in the area, nor any documented history of

mining claim Mineral rights are property rights to exploit an area for the minerals it harbors. Mineral rights can be separate from property ownership (see Split estate). Mineral rights can refer to sedentary minerals that do not move below the Earth's surfa ...

s; the closest mines are located to the west in the Blue River mining district. The volcanic vents throughout the Mount Washington Wilderness are underlain by

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

to Pliocene volcanic rock layers, which do not contain hydrocarbons for fossil fuels. While there is relatively little potential for

geothermal energy Geothermal energy is the thermal energy in the Earth's crust which originates from the formation of the planet and from radioactive decay of materials in currently uncertain but possibly roughly equal proportions. The high temperature and pre ...

in the High Cascades, there are

hot spring A hot spring, hydrothermal spring, or geothermal spring is a spring produced by the emergence of geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow bodies of magma (molten rock) or by c ...

s along the western edge of the mountain range. The Belknap Hot Spring lies to the southwest of the wilderness area, ejecting water at a rate of per minute with a temperature of .

Ecology

Described by Wuerthner (2003) as a "rocks and ice wilderness," much of the Mount Washington Wilderness consists of lava flows and rubble. However, it does include some forested areas, as well as 28 lakes in the northern and southwestern parts of the space. Vegetation in the area includes

mountain hemlock ''Tsuga mertensiana'', known as mountain hemlock, is a species of hemlock native to the west coast of North America, found between Southcentral Alaska and south-central California. Description ''Tsuga mertensiana'' is a large evergreen conifer ...

lodgepole pine ''Pinus contorta'', with the common names lodgepole pine and shore pine, and also known as twisted pine, and contorta pine, is a common tree in western North America. It is common near the ocean shore and in dry montane forests to the subalp ...

ponderosa pine ''Pinus ponderosa'', commonly known as the ponderosa pine, bull pine, blackjack pine, western yellow-pine, or filipinus pine is a very large pine tree species of variable habitat native to mountainous regions of western North America. It is t ...

, and

whitebark pine ''Pinus albicaulis'', known by the common names whitebark pine, white bark pine, white pine, pitch pine, scrub pine, and creeping pine, is a conifer tree native to the mountains of the western United States and Canada, specifically subalpine ...

. Ponderosa pine occurs at the eastern base of the volcano, with

Douglas fir The Douglas fir (''Pseudotsuga menziesii'') is an evergreen conifer species in the pine family, Pinaceae. It is native to western North America and is also known as Douglas-fir, Douglas spruce, Oregon pine, and Columbian pine. There are thre ...

on the western side. Vegetation is sparse on lava-covered surfaces. Mountain hemlock, however, also grows on lava flows, and there is an

understory In forestry and ecology, understory (American English), or understorey (Commonwealth English The use of the English language in current and former member countries of the Commonwealth of Nations was largely inherited from British co ...

beargrass ''Xerophyllum tenax'' is a North American species of plants in the corn lily family. It is known by several common names, including bear grass, soap grass, quip-quip, and Indian basket grass. Ecology ''Xerophyllum tenax'' has flowers with si ...

huckleberry Huckleberry is a name used in North America for several plants in the family Ericaceae, in two closely related genera: ''Vaccinium'' and ''Gaylussacia''. The huckleberry is the state fruit of Idaho. Nomenclature The name 'huckleberry' is a Nort ...

, and

rhododendron ''Rhododendron'' (; from Ancient Greek ''rhódon'' "rose" and ''déndron'' "tree") is a very large genus of about 1,024 species of woody plants in the heath family (Ericaceae). They can be either evergreen or deciduous. Most species are nativ ...

. Animal life includes large animals such as deer and elk, with the rare

American black bear The American black bear (''Ursus americanus''), also called simply a black bear or sometimes a baribal, is a medium-sized bear endemic to North America. It is the continent's smallest and most widely distributed bear species. American black bea ...

cougar The cougar (''Puma concolor'') is a large cat native to the Americas. Its range spans from the Canadian Yukon to the southern Andes in South America and is the most widespread of any large wild terrestrial mammal in the Western Hemisphere. I ...

. Smaller animals like

pika A pika ( or ; archaically spelled pica) is a small, mountain-dwelling mammal found in Asia and North America. With short limbs, very round body, an even coat of fur, and no external tail, they resemble their close relative, the rabbit, but w ...

marmot Marmots are large ground squirrels in the genus ''Marmota'', with 15 species living in Asia, Europe, and North America. These herbivores are active during the summer, when they can often be found in groups, but are not seen during the winter, w ...

marten A marten is a weasel-like mammal in the genus ''Martes'' within the subfamily Guloninae, in the family Mustelidae. They have bushy tails and large paws with partially retractile claws. The fur varies from yellowish to dark brown, depending on ...

snowshoe hare The snowshoe hare (''Lepus americanus''), also called the varying hare or snowshoe rabbit, is a species of hare found in North America. It has the name "snowshoe" because of the large size of its hind feet. The animal's feet prevent it from sin ...

s, and

ground squirrel Ground squirrels are members of the squirrel family of rodents (Sciuridae), which generally live on or in the ground, rather than trees. The term is most often used for the medium-sized ground squirrels, as the larger ones are more commonly known ...

s are also found in the area. Lakes in the wilderness sustain populations of brook trout,

cutthroat trout The cutthroat trout is a fish species of the family Salmonidae native to cold-water tributaries of the Pacific Ocean, Rocky Mountains, and Great Basin in North America. As a member of the genus ''Oncorhynchus'', it is one of the Pacific ...

, and

rainbow trout The rainbow trout (''Oncorhynchus mykiss'') is a species of trout native to cold-water tributaries of the Pacific Ocean in Asia and North America. The steelhead (sometimes called "steelhead trout") is an anadromous (sea-run) form of the coast ...

, and frogs can be observed around some of them.

Human history

The barrenness of Mount Washington's surroundings means that it has seen little historical recreational use. A wagon road at McKenzie Pass was built in 1872, which was later paved during the 1930s and became Oregon Route 242. It received its name from the nearby McKenzie River, which in turn derived its name from Donald McKenzie, a fur trader who explored the area in 1812. On August 26, 1923, Mount Washington was climbed for the first time by six boys from Bend: Ervin McNeal, Phil Philbrook, Armin Furrer, Wilbur Watkins, Leo Harryman, and Ronald Sellars. Before Mount Washington's surroundings were designated a wilderness area in 1964, the Willamette National Forest administration had planned to open them to commercial timber production to address a shortage in Lane County, asserting that the land had little aesthetic or recreational merit. The area was established anyway, as Forest Service agents argued it would improve "wilderness".

Geology

Volcanism in the Oregon segment of the Cascade Range results from intra-range

rift In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-grabe ...

s and the

of the Juan de Fuca tectonic plate under the North American tectonic plate. Mount Washington forms part of the High Cascades physiographic region in central Oregon, an arc of

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Quaternary

lava flow Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...

s, and

fissure vent A fissure vent, also known as a volcanic fissure, eruption fissure or simply a fissure, is a linear volcanic vent through which lava erupts, usually without any explosive activity. The vent is often a few metres wide and may be many kilo ...

s that trend from north to south, with occasional large

stratovolcano A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and p ...

es. Near Mount Washington, the High Cascades form a lava field with high-alumina, diktytaxitic

erupted from cinder cones. These volcanoes have been eroded by glaciers and reduced to buttes in the Cascade arc, and much of the vents in the area were covered by Mount Washington. Some basalt lava flows occur on the edges of Mount Washington at the Cache Creek and Dry Creek canyons or as

outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. Features Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficia ...

s that form benches (long, relatively narrow strips of relatively level or gently inclined land bounded by distinctly steeper slopes above and below) about away from Washington from Patjens Lake to the McKenzie River. Washington is part of the informal group of volcanoes known as Oregon's Matterhorns, which includes Mount Thielsen, Three Fingered Jack, Mount Bailey, and Diamond Peak. The name originates from the spire-like appearance of the volcanoes' summits, which resembles the pinnacle of the

Matterhorn The (, ; it, Cervino, ; french: Cervin, ; rm, Matterhorn) is a mountain of the Alps, straddling the main watershed and border between Switzerland and Italy. It is a large, near-symmetric pyramidal peak in the extended Monte Rosa area of th ...

in Switzerland. They all ceased eruptive activity at least 100,000 to 250,000 years ago, leading to their extensive dissection by glaciers over time. Mount Washington is also part of the Sisters Reach subsegment, which extends for and contains at least 466 volcanoes that were active during the Quaternary. Washington represents one of 30

(rich in magnesium and iron) stratovolcanoes and shield volcanoes in the group, which include Pleistocene and Holocene eruptive centers. The volcano and its wilderness area sit on a lava platform with an altitude of , and they are bounded by faults to the east and west. Volcanic rocks contained within the wilderness area are either composed of older basalt or younger basaltic andesite, all of which were produced during the Quaternary, probably during the past 700,000 years. Pleistocene deposits show evidence of erosion by glaciers. Holocene deposits, dated between 3,000 and 1,500 years old, encompass about half of the wilderness area, and they also occur outside the wilderness area at its northwestern and southern borders. Mount Washington Oregon

Whether Mount Washington is a stratovolcano or

shield volcano A shield volcano is a type of volcano named for its low profile, resembling a warrior's shield lying on the ground. It is formed by the eruption of highly fluid (low viscosity) lava, which travels farther and forms thinner flows than the more v ...

is debated within the literature. Wood and Kienle (1990) refer to it as a "mafic shield volcano," and the

Global Volcanism Program The Smithsonian Institution's Global Volcanism Program (GVP) documents Earth's volcanoes and their eruptive history over the past 10,000 years. The mission of the GVP is to document, understand, and disseminate information about global volcanic act ...

of the

Smithsonian Institution The Smithsonian Institution ( ), or simply the Smithsonian, is a group of museums and education and research centers, the largest such complex in the world, created by the U.S. government "for the increase and diffusion of knowledge". Founded ...

also considers it a shield volcano with a pyroclastic cone. Sherrod et al. (2004) classify Mount Washington as a "steep-sided" shield volcano. E. M. Taylor describes Mount Washington as a stratovolcano cone that reaches an elevation of above an older shield volcano, referring to it as "a glacially-gutted Pleistocene stratovolcano." Hildreth (2007) likewise calls it a "a glacially sculpted mafic stratocone ..with a broad apron of mafic lavas." In his argument for classifying Mount Washington as a stratovolcano, Hildreth adds that it is made of composite materials with steep slopes and a high relief of . However, Hildreth acknowledges that there is morphological continuity from steep mafic cones into transitional, cone-shaped shield volcanoes like Olallie Butte. Mount Washington has a diameter of about . It has a summit cone, a

comprised by cinder, lava flows, and

intrusive rock Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form '' intrusions'', such as batholiths, dikes, sills, laccoliths, and volcanic necks.Intrusive RocksIntrusive rocks accessdate: Marc ...

that covers Washington's volcanic conduit. This plug is made of micronorite with a diameter of . There are dikes exposed throughout the summit cone, mostly oriented from north to south, with another dike swarm trending north from the central plug. The summit formed over a platform of basaltic andesite lavas from early eruptions at Mount Washington, made of thinner flows combined with

pyroclastic rock Pyroclastic rocks (derived from the el, πῦρ, links=no, meaning fire; and , meaning broken) are clastic rocks composed of rock fragments produced and ejected by explosive volcanic eruptions. The individual rock fragments are known as pyroc ...

. The volcano has a mafic composition, with subalkaline basalt and basaltic andesite. Lava flows from Washington exhibit

breccia Breccia () is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix. The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of d ...

with

plagioclase Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more pro ...

and

olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers qui ...

, with

palagonite Palagonite is an alteration product from the interaction of water with volcanic glass of chemical composition similar to basalt. Palagonite can also result from the interaction between water and basalt melt. The water flashes to steam on contact w ...

tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock ...

at the northeastern slope of the mountain that might indicate a past

subglacial eruption Subglacial eruptions, those of ice-covered volcanoes, result in the interaction of magma with ice and snow, leading to meltwater formation, jökulhlaups, and lahars. Flooding associated with meltwater is a significant hazard in some volc ...

during Washington's cone-building phase. Mount Washington has been eroded over time and is now very dissected, with its inner contents exposed and U-shaped canyons and

cirque A (; from the Latin word ') is an amphitheatre-like valley formed by glacial erosion. Alternative names for this landform are corrie (from Scottish Gaelic , meaning a pot or cauldron) and (; ). A cirque may also be a similarly shaped landf ...

s. In the late Pleistocene, large glaciers extending more than to the east and west carved cirques into the slopes of the volcano. The George Lake and Dry Creek cirques, which face north and northeast, respectively, show evidence of holding glaciers similar to those documented at Canyon Creek cirque on Three Fingered Jack with moraines. Wood and Kienle (1990) estimate that Mount Washington once extended to an elevation of , with an elevation of above the basalt lava field surrounding it.

Subfeatures

The Global Volcanism Program considers Cache Mountain, Little Cache Mountain, Hayrick Butte, and Hoodoo Butte subsidiary cones of Mount Washington. The Mount Washington Wilderness includes a number of cinder cones, typically with elevations between . Composed of gray to red cinder, they also have

scoria Scoria is a pyroclastic, highly vesicular, dark-colored volcanic rock that was ejected from a volcano as a molten blob and cooled in the air to form discrete grains or clasts.Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, eds. (2005) ' ...

and welded spatter. Major cinder cones in the wilderness include Belknap Crater, Twin Craters,

Scott Mountain Scott Mountain, Lane County, Oregon There are two mountains in Oregon commonly called Scott Mountain. The Scott Mountain (further north) in the Willamette National Forest, is sometimes confused with and referred to as Olallie Mountain; while so ...

, and the Sand Mountain craters. MtWashington Belknap BB 150509

Eruptions from a chain of spatter cones mark the most recent activity at Mount Washington. About one mile in length, they trend northeast, with their mid-section parallel to depressions in the Cache Creek valley between Mount Washington and Blue Lake Crater. The northernmost vent of Mount Washington has a depth of and likely only ever erupted volcanic gas. The first group of four spatter cones lies to the south, with depths ranging from . Farther south, there are seven other vents, including three small craters separated from three larger vents to the south by a

graben In geology, a graben () is a depressed block of the crust of a planet or moon, bordered by parallel normal faults. Etymology ''Graben'' is a loan word from German, meaning 'ditch' or 'trench'. The word was first used in the geologic contex ...

, as well as a central crater with a small crater on the northern side of its rim.

Mount Washington basaltic andesite

There are four major types of basalt and basaltic andesite in the central Cascades: early high-alumina olivine tholeiitic (HAOT) basalt, normal High Cascade HAOT basalt, North Sister basaltic andesites, and Mount Washington type basaltic andesites. Hughes (1990) argues that their differences could be the result of different magma sources or magma evolution in open systems. Mount Washington basaltic andesites are also considered one of the three distinct mafic rock types in the High Cascade platform, with North Sister basaltic andesites and normal basalts. The three groups all exhibit different major and trace element abundances. Mount Washington basaltic andesite is more common than North Sister basaltic andesite, with higher levels of incompatible elements and

rare-earth element The rare-earth elements (REE), also called the rare-earth metals or (in context) rare-earth oxides or sometimes the lanthanides (yttrium and scandium are usually included as rare earths), are a set of 17 nearly-indistinguishable lustrous silv ...

s. It also extends to the east and west of the major Cascade arc. Otherwise, the Mount Washington and North Sister basaltic andesites display lithologic similarities including a dearth of

pyroxene The pyroxenes (commonly abbreviated to ''Px'') are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents calcium (Ca), sodium (Na), iron (Fe II) ...

phenocryst 300px, Swiss side of the Mont Blanc massif, has large white plagioclase phenocrysts, triclinic minerals that give trapezoid shapes when cut through). 1 euro coins, 1 euro coin (diameter 2.3 cm) for scale. A phenocryst is an early forming, relati ...

s and

augite Augite is a common rock-forming pyroxene mineral with formula . The crystals are monoclinic and prismatic. Augite has two prominent cleavages, meeting at angles near 90 degrees. Characteristics Augite is a solid solution in the pyroxene group ...

microphenocrysts, and both groups were probably near-primary melts. According to Hughes (1982), examples of Mount Washington basaltic andesites occur at Holocene deposits from Nash Crater, Four-in-One Cone, and Little Belknap Cone, as well as undated deposits at Todd Lake Volcano, Falls Creek,

Broken Top Broken Top is a glacially eroded complex stratovolcano. It lies in the Cascade Volcanic Arc, part of the extensive Cascade Range in the U.S. state of Oregon. Located southeast of the Three Sisters peaks, the volcano, residing within the Three S ...

, and the abutment of Tumalo Dam.

Eruptive history

Mount Washington formed during the late Pleistocene epoch; the volcano itself is not older than a few hundred thousand years. Harris (2005) estimates that it has not erupted for more than 250,000 years, similar to Mount Thielsen; this date is supported by James, Manga, and Rose (1999).

Paleomagnetic Paleomagnetism (or palaeomagnetismsee ), is the study of magnetic fields recorded in rocks, sediment, or archeological materials. Geophysicists who specialize in paleomagnetism are called ''paleomagnetists.'' Certain magnetic minerals in rocks ...

evidence suggests that the volcano and associated lava flows exhibit normal magnetic polarity. Its volcanic edifice was produced through the eruption of basaltic andesite and mafic

volcanic ash Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, created during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to refer ...

, the latter being preserved as palagonite tuff along the northeastern and southwestern flanks of the summit cone. Compared to larger stratovolcanoes in the Cascade volcanic arc, Mount Washington, like the rest of Oregon's Matterhorns, had a relatively short eruptive life. Several spatter cones produced basaltic andesite on the lower northeastern side of the volcano, following a

fissure A fissure is a long, narrow crack opening along the surface of Earth. The term is derived from the Latin word , which means 'cleft' or 'crack'. Fissures emerge in Earth's crust, on ice sheets and glaciers, and on volcanoes. Ground fissure A ...

that reached from Washington's summit. There were no lava flows from this eruption, nor at an eruption at the nearby Blue Lake Crater, which produced volcanic material that displayed petrographic similarities to the Mount Washington splatter cone deposits. These include similar

porphyritic Porphyritic is an adjective used in geology to describe igneous rocks with a distinct difference in the size of mineral crystals, with the larger crystals known as phenocrysts. Both extrusive and intrusive rocks can be porphyritic, meaning a ...

textures with 10 to 15 percent plagioclase phenocrysts as well as similar alignments, suggesting that they erupted simultaneously. Sherrod et al. (2004) argue that the spatter cones and activity from Blue Lake Crater represent the most recent eruptions near the McKenzie Pass and

Santiam Pass Santiam is a place name of the U.S. state of Oregon, referring to the indigenous Santiam people. It may refer to: * Santiam Academy * Santiam Hospital * Santiam Junction, Oregon * Santiam Junction State Airport * Santiam Pass * Santiam River ...

region. It is still possible that new volcanic cones could be produced at the base of Mount Washington. However, according to Taylor, Causey, and MacLeod (1983), the volcano itself is unlikely to still be active.

Recreation

While the area is not used as frequently as many other wilderness areas in the Oregon branch of the Cascade Range, it offers scenic lakes and trails. The Pacific Crest Trail passes over the western side of Mount Washington. Other trails include a loop around the Patjens Lakes, the Hand Lake trail, and the Benson Lake route. The U.S. National Geodetic Survey Data Sheet for Mount Washington notes that climbing the volcano is challenging and dangerous and thus is not recommended for inexperienced climbers or climbers without proper equipment.

Notes

* According to Hildreth's definitions, proximal relief refers to the difference between the summit elevation and the highest exposure of old rocks under the main edifice, while draping relief marks the difference between the summit elevation and the edifice's lowest distal lava flows (excluding pyroclastic and debris flows).

References

Sources

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External links

* {{DEFAULTSORT:Washington, Mount (Oregon) Cascade Range Cascade Volcanoes Deschutes National Forest Landmarks in Oregon Mountains of Deschutes County, Oregon Mountains of Linn County, Oregon Pleistocene shield volcanoes Polygenetic shield volcanoes Shield volcanoes of the United States Subduction volcanoes Volcanic plugs of the United States Volcanoes of Deschutes County, Oregon Volcanoes of Linn County, Oregon Willamette National Forest Stratovolcanoes of Oregon