Mount Bachelor, formerly named Bachelor Butte, is a dormant stratovolcano atop a shield volcano in the Cascade Volcanic Arc and the Cascade Range of central

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

. Named Mount Bachelor because it stands apart from the nearby Three Sisters, it lies in the eastern segment of the central portion of the High Cascades, the eastern segment of the Cascade Range. The volcano lies at the northern end of the long Mount Bachelor Volcanic Chain, which underwent four major eruptive episodes during the

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), 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 fina ...

and the

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 ...

. The

United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

considers Mount Bachelor a moderate threat, but Bachelor poses little threat of becoming an

active volcano An active volcano is a volcano which is either erupting or is likely to erupt in the future. An active volcano which is not currently erupting is known as a dormant volcano. Overview Tlocene Epoch. Most volcanoes are situated on the Pacific ...

in the near future. It remains unclear whether the volcano is

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

or just inactive. The Mount Bachelor ski area has operated on the mountain since 1958, and the volcano's summit hosts the Mount Bachelor Observatory. A center of winter recreation, the area offers snowshoeing, snow skiing,

snow tubing Tubing, also known as inner tubing, bumper tubing, towed tubing, or kite tubing, is a recreational activity where an individual rides on top of an inner tube, either on water, snow, or through the air. The tubes themselves are also known as "donu ...

, and dog sledding, among other activities. The summit can be reached by a climbing trail that travels over lava from the volcano.

Geography

Mount Bachelor lies in the Cascade Range, within Deschutes County, in the U.S. state of

. It is located south of the Three Sisters complex volcano, and reaches an elevation of . It rises above its base, with a proximal

relief Relief is a sculptural method in which the sculpted pieces are bonded to a solid background of the same material. The term '' relief'' is from the Latin verb ''relevo'', to raise. To create a sculpture in relief is to give the impression that th ...

of . The volcano has a volume of . Mount Bachelor stands southeast of the

Tumalo Mountain Tumalo Mountain is a shield volcano in the Cascade Range of central Oregon, located just northeast of Mount Bachelor across the Cascade Lakes Scenic Byway. Climb, the views Ice age glaciers carved a large cirque into the northeast flank of ...

volcano and to the southwest of the city of Bend, in the Deschutes National Forest. Weather varies greatly in the area due to the rain shadow caused by the Cascade Range. Air from the Pacific Ocean rises over the western slopes, which causes it to cool and dump its moisture as rain (or snow in the winter). Precipitation increases with elevation. Once the moisture is wrung from the air, it descends on the eastern side of the crest, which causes the air to be warmer and drier. On the western slopes, precipitation ranges from annually, while precipitation over the eastern slopes varies from in the east. Temperature extremes reach in summers and during the winters.

Geology

Mount Bachelor joins several other volcanoes in the eastern segment of the Cascade Range known as the High Cascades, which trends north–south. Constructed towards the end of the Pleistocene Epoch, these mountains are underlain by more ancient volcanoes that subsided due to parallel north–south faulting in the surrounding region. Bachelor lies in the eastern segment of the central portion of the High Cascades. Mount Bachelor is the youngest prominent volcano in the Three Sisters area of Oregon, a group of closely grouped volcanic peaks, in contrast to the typical spacing between volcanoes elsewhere in the Cascades. Among the most active volcanic areas in the Cascades and one of the most densely populated volcanic centers in the world, the Three Sisters region includes peaks such as Belknap Crater,

Mount Washington Mount Washington is the highest peak in the Northeastern United States at and the most topographically prominent mountain east of the Mississippi River. The mountain is notorious for its erratic weather. On the afternoon of April 12, 1934 ...

, Black Butte, and

Three Fingered Jack Three Fingered Jack is a summit of a shield volcano of the Cascade Range in the U.S. state of Oregon. Formed during the Pleistocene epoch, the mountain consists mainly of basaltic andesite lava and was heavily glaciated in the past. While othe ...

to the north, and

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 Mount Bachelor to the south. Most of the surrounding volcanoes consist 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 in ...

(rich in magnesium and iron) lavas; only South and Middle Sister have an abundance of

silicic Silicic is an adjective to describe magma or igneous rock rich in silica. The amount of silica that constitutes a silicic rock is usually defined as at least 63 percent. Granite and rhyolite are the most common silicic rocks. Silicic is the grou ...

rocks such as

andesite Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predo ...

dacite Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained ( aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyo ...

, and

rhyodacite Rhyodacite is a volcanic rock intermediate in composition between dacite and rhyolite. It is the extrusive equivalent of those plutonic rocks that are intermediate in composition between monzogranite and granodiorite. Rhyodacites form from ra ...

. Mafic magma is less

viscous The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the in ...

; it produces lava flows and is less prone to explosive eruptions than silicic magma. The Mount Bachelor volcanic chain, southeast of South Sister, consists of Mount Bachelor, which is the largest and northernmost volcano of the group, and a series of cinder cones, lava flows, and three shield volcanoes. The chain runs for and encompasses an area of about , trending from north to south. Its volcanoes show significant variation in size and shape, ranging from steep cones produced by mild explosive activity to the gently sloping profiles of shield volcanoes. Volcanic vents within the locale show north–northwest–north–northeast-trending trends, which correspond to normal faults (where one side of the fault moves downward relative to the other) in the region, including one at the Bachelor chain's southern end. The Bachelor chain shows that much of the Quaternary Cascades in Oregon were produced in short bursts of eruptive activity and that mafic shield volcanoes can erupt at equal rates to stratovolcanoes. The volcanoes within the field are fed by shallow, compartmentalized magma chambers. A stratovolcano (atop a shield volcano with a symmetrical shape), Mount Bachelor formed between 18,000 and 8,000 years ago. Bachelor is composed of

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 ...

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 Am ...

, and though its upper volcanic cone formed after its base shield, the two edifices show similar eruptive composition. The mountain has withstood very little alteration as a result of glacial erosion besides a small cirque (an amphitheatre-like valley formed by glacial erosion) on the northern side of the volcano. Despite the small scale of this erosion, it has extensively altered the northern face of Mount Bachelor, breaking down its lava into fine powder, particularly at the

glacier terminus A glacier terminus, toe, or snout, is the end of a glacier at any given point in time. Although glaciers seem motionless to the observer, in reality glaciers are in endless motion and the glacier terminus is always either advancing or retreati ...

, where the terminal moraine resembles dust. However, the volcano's glacier has shrunk in recent decades and may vanish as a result of the warming climate. The volcano's summit has a number of clustered, northwest–southeast-trending vents, which erupted block lava flows made of basalt and andesite and only exhibited minor explosive eruptions, as little

tephra Tephra is fragmental material produced by a volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, they r ...

can be found near the vents at the summit; there is also little

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 pyrocl ...

. There is no summit crater. Lava flows from Mount Bachelor's summit feature phenocrysts including clinopyroxene,

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 ...

(more rare), and

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 p ...

, with two phases for the clinopyroxene featuring augite and pigeonite. Textures for these eruptive products vary from intersectal to intergranular, seriate to glomeroporphyritic to subophitic, and

trachytic Trachyte () is an extrusive igneous rock composed mostly of alkali feldspar. It is usually light-colored and aphanitic (fine-grained), with minor amounts of mafic minerals, and is formed by the rapid cooling of lava enriched with silica and alk ...

to non-aligned. Bachelor last erupted between 10,000 and 8,000 years ago, and is entirely covered with Mazama Ash from the catastrophic eruption of Mount Mazama about 6,845 years ago. There is no geothermal activity at present, though some areas popularly thought to be fumaroles are caused by air movement through the porous structure. Several are near the top of the Pine Marten chairlift and occasionally present a hazard to skiers and snowboarders where the snow is undermined.

Subfeatures

Mount Bachelor is associated with a number of pyroclastic cones and shield volcanoes. Nearby cones include Dry Butte, Egan Cone, Katsuk Butte, Kwolh Butte, Lolah Butte, Lumrum Butte, Red Crater, Sheridan Mountain, Siah Butte, Talapus Butte, Three Trappers, and Tot Mountain. Shield volcanoes within the vicinity of Bachelor include Sheridan Mountain,

Lookout Mountain Lookout Mountain is a mountain ridge located at the northwest corner of the U.S. state of Georgia, the northeast corner of Alabama, and along the southeastern Tennessee state line in Chattanooga. Lookout Mountain was the scene of the 18th-centu ...

, and Kwohl Butte.

Eruptive history

The Mount Bachelor Chain has shown activity during the Pleistocene and the Holocene, mostly consisting of effusive eruptions with a small number of explosive eruptions yielding agglutinate

spatter cones 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 ...

, volcanic bombs, and scoria. Within the Bachelor chain, mafic (rich in magnesium and iron) eruptive activity consisting mostly of lava flows and tephra fall took place over four discrete periods, beginning approximately 18,000 to 15,000 years ago as a Pleistocene glacier in the area began to retreat. During this first eruptive episode, the majority of activity occurred in the center of the chain, forming the Sheridan Mountain shield volcano. The first vents to erupt,

subglacial volcano A subglacial volcano, also known as a glaciovolcano, is a volcanic form produced by subglacial eruptions or eruptions beneath the surface of a glacier or ice sheet which is then melted into a lake by the rising lava. Today they are m ...

es beneath an ice sheet west of Sparks Lake in the northwestern segment of the chain, interacted with water to produce violent explosive eruptions that ejected pyroclastic rock, which was deposited into the lakebed. Hyaloclastite deposits and thick lava flows with ice also formed in this area, along with the Talapus and Katsuk Buttes from scoria produced by later, milder Strombolian eruptions (which eject incandescent cinder, lapilli, and volcanic bombs). The second eruptive period consisted of explosive eruptions, which constructed scoria cones and lava flows to the south of Sheridan Mountain, known as the Siah Butte vents. These extend to the south end of the chain. The third period produced the shield volcano beneath Mount Bachelor out of basaltic andesite, later constructing its summit, in addition to a shield volcano that is topped by the Kwohl Butte. ʻAʻā lava erupted from Mount Bachelor during this third period coursed down its northern and northwestern sides. By 12,000 years ago, Mount Bachelor was close to its current size, as the oldest moraines from glaciers on the mountain (which are covered by lava flows from this third eruptive episode) can be dated to this time period. The current edifice at Mount Bachelor had been finished by about 10,000 years ago, followed by a gap in eruptive activity that lasted for 2,000 years. The latest eruptive activity within the chain yielded scoria cones and lava flows, including the Egan cone, which can be observed on Mount Bachelor's lower northern flank. Due to the presence of Mazama Ash on the northern side of the volcano, no eruptive activity is likely to have happened since 7,700 years ago. In total, the Mount Bachelor chain has produced of eruptive material, including Mount Bachelor's volume at . Stratigraphic and

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 rock ...

studies suggest that Bachelor's volume was produced in as little as 1,500 years.

Potential hazards

Listed at a "moderate" threat level by the

, Mount Bachelor poses little threat of becoming an

in the near future. It may be part of a monogenetic volcanic field, meaning that the volcano only underwent one long series of eruptions before stopping activity altogether, but it may just be inactive, and it could erupt in the future. It remains unclear whether Mount Bachelor is merely dormant or whether it is completely

. The Bachelor volcanic chain lies within a lava flow hazard zone that exists in central Oregon, and eruptions from this field of mafic volcanoes may produce eruptions of tephra and lava flows extending for from their source vents. Within areas of the vents, tephra may form deposits with thicknesses of up to , though they only reach thicknesses of at further distances beyond . Because lava flows move slowly, they can be outmaneuvered by animals and humans, though they do pose a threat to streams and rivers, which they may dam or divert, leading to potential flood risks. If Mount Bachelor were to erupt, it would significantly affect the ski industry on the volcano, endangering visitors. An eruption from Mount Bachelor, the Three Sisters to the north, or another nearby vent in the Mount Bachelor Chain may be unlikely, but any would pose threats to the ski area.

Human history

Mount Bachelor is so called because it "stands apart" from the Three Sisters, a group of three volcanic mountains that are northwest of Mount Bachelor. In early days Bachelor Butte was frequently called "Brother Jonathan", or "Mount Brother", but both eventually fell out of use. Around the time of

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...

, 90,000 soldiers were stationed to train at

Camp Abbot Camp Abbot was a military training center in the northwest United States, located in central Oregon south of Bend. Active for less than sixteen months, the U.S. Army camp was used to train combat engineers during World War II and was named for ...

near Bend. During the war, Bend's community depended on

sawmill A sawmill (saw mill, saw-mill) or lumber mill is a facility where logging, logs are cut into lumber. Modern sawmills use a motorized saw to cut logs lengthwise to make long pieces, and crosswise to length depending on standard or custom sizes ...

s and agriculture, with a small ski area opening at Mount Bachelor in 1941. In 1950, the Shevlin-Hixon mill closed, leaving hundreds unemployed before it was re-expanded several years later. By 1958, the ski hill had grown into a ski resort, after the fundraising of start-up costs by the Bend Skyliners Mountaineering Club, with the installation of the first chair lift in 1962 and the attainment of a 30-year special use permit from the United States Forest Service. Expansion continued into the 1970s, with the ski area receiving 257,000 visitors between 1974 and 1975, and more than 500,000 between 1982 and 1983. The resort developers were concerned that skiing on a butte might be perceived by consumers as "small-time" and so named their resort Mount Bachelor. Over time the popularity of the ski area led to the name Mount Bachelor coming into popular usage, and in a divided decision, the Oregon Geographic Names Board voted to change the name from Bachelor Butte to Mount Bachelor. In the 1980s, struggles of the homebuilding and lumber industries meant that Deschutes County saw a 15 percent unemployment rate, but construction of a local mall, a chair to the top of Mount Bachelor, and the High Desert Museum helped the economy improve with time. In 2013, the United States Forest Service approved a new master plan for further development of the resort, including a mountain bike park, more chair lifts, more trails, a zip line, and improved lodge amenities. The volcano's summit hosts the Mount Bachelor Observatory, located at an elevation of above sea level, and maintained by a research group at the

University of Washington Bothell The University of Washington Bothell (UW Bothell) is a branch campus of University of Washington in Bothell, Washington. It was founded in 1989 and is located just northwest of the junction of Interstate 405 and State Route 522, and it shares ...

and the ski resort. Research at the observatory investigates long-range transport of pollution from the Asian continent, measuring chemical features of plumes that reach the

Pacific Northwest The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Thou ...

Recreation

Mount Bachelor ski area operates a chairlift during the summer as well as during the ski season (weather permitting), making it the only major Cascade volcano with a chairlift to the summit. Nationally known, the resort is one of the largest in the Pacific Northwest with a skiable area of and a vertical drop of , in addition to six

terrain park A terrain park or snow park is an outdoor recreation area containing terrain that allows skiers, snowboarders and snowbikers to perform tricks. Terrain parks have their roots in skateparks and many of the features are common to both. From thei ...

s. The resort represents a center of winter recreational activities within Deschutes County, operating within the Deschutes National Forest and partnering with the United States Forest Service to offer activities while preserving the Oregon Cascades and the forest area. The resort offers interpretive tours with a naturalist on local flora and fauna, in addition to snowshoeing, snowboarding,

, dog sledding, and department stores. During the summer,

fishing Fishing is the activity of trying to catch fish. Fish are often caught as wildlife from the natural environment, but may also be caught from fish stocking, stocked bodies of water such as fish pond, ponds, canals, park wetlands and reservoirs. ...

is a popular activity in the local lakes and streams, as is hiking and camping. Climbing to the top of Mount Bachelor follows a trail that begins at an elevation of and gains to reach the summit. A single-track trail, it traverses over lava from the volcano, which appears in jagged formations. The volcano's summit offers views of the rest of the Mount Bachelor chain to the south, in addition to Lookout Mountain, the Three Sisters, Mount Jefferson, Mount Hood, and Mount Adams in Washington state.

Notes

* Other sources list the elevation at . * Hildreth (2007) mentions five eruptive periods.

References

Sources

* * * * * * * * * * * * *

External links

Mount Bachelor ski area

{{DEFAULTSORT:Bachelor, Mount Cascade Range Cascade Volcanoes Deschutes National Forest Dormant volcanoes Landmarks in Oregon Mountains of Deschutes County, Oregon Mountains of Oregon Shield volcanoes of the United States Stratovolcanoes of the United States Subduction volcanoes Volcanoes of Deschutes County, Oregon Volcanoes of Oregon