| Black Butte | |
|---|---|
 | |
| Highest point | |
| Elevation | 6,436 ft (1,962 m) NAVD 88[1] |
| Prominence | 3,076 ft (938 m)[2] |
| Coordinates | 44°23′59″N121°38′08″W / 44.399724139°N 121.635477517°W /44.399724139; -121.635477517[1] |
| Geography | |
  Black Butte Black Butte (the United States) Show map of the United States | |
| Parent range | Cascade Range |
| Topo map | USGS Black Butte[3] |
| Geology | |
| Rock age | Pleistocene |
| Mountain type | Stratovolcano[4] |
| Volcanic arc | Cascade Volcanic Arc |
| Last eruption | About 1,430,000 years ago[5] |
| Climbing | |
| Easiest route | Hike |
Black Butte is anextinctstratovolcano in theU.S. state ofOregon. Located inJefferson County, it is part ofDeschutes National Forest. Black Butte forms part of theCascade volcanic arc. The butte lies just south of theMetolius Springs, which merge to form theheadwaters of theMetolius River. The Metolius River's basin sustains a wide array of plant life, large and small mammals, and more than 80 bird species.
Black Butte last erupted during thePleistocene; geologists have estimated its age at 0.4, 0.5, and 1.43 ± 0.33 million years ago. The duration of the eruptions that built the volcano remains unclear, though the activity likely coincided with large-scaleblock faulting in the vicinity of the Metolius Springs. Black Butte has a prominentvolcanic cone and is made up ofmafic (rich in magnesium and iron)basaltic andesite lava. Despite having a well-preserved, symmetrical shape and an unexposedpyroclastic core, the butte has undergone moderate erosion, with shallowravines, deepgullies on its sides, and rocks withweathering rinds. A number ofcinder cones and avolcanic field also lie nearby the butte.
There was afire lookout ground house on the butte, which was burned down by theUnited States Forest Service in 2016. A whitecupola structure sits on the top of the butte as well as a more modern fire lookout tower. The resort communityBlack Butte Ranch lies nearby and offers recreational activities likehorseback riding,biking,hiking,canoeing,kayaking, andpaddleboarding; during the winter, activities includeNordic skiing andsnowshoeing.
Black Butte lies about 21 miles (34 km) to the southeast ofMount Jefferson and about 8.6 miles (13.8 km) northwest of the junction ofU.S. Route 126 andU.S. Route 20, at the eastern edge of the city ofSisters. The butte is part ofJefferson County in theU.S. state ofOregon.[1][3] Other volcanoes such asThree Fingered Jack andMount Washington lie about 10 miles (16 km) to the west.[6]
According to theU.S. National Geodetic Survey and scientists from theUnited States Geological Survey, Black Butte has an elevation of 6,436 feet (1,962 m);[1][7] theGeographic Names Information System database lists its elevation as 6,430 feet (1,960 m),[3] whileOregon Geographic Names lists its elevation at 6,415 feet (1,955 m).[8][a] The butte has proximal and drapingreliefs of 2,490 feet (760 m) and 3,150 feet (960 m), which are the "difference between summit elevation and that of highest exposure of older rocks overlain by the edifice" and the "difference between summit elevation and that of lowest distal lavas of the edifice (not including distal pyroclastic or debris flows)," respectively.[7] According to E. M. Taylor, Black Butte has a diameter of 4 miles (6.4 km).[9]
The U.S. National Geodetic Survey report describes Black Butte as a "very prominent" mountain;[1] it is an imposing feature and landmark in the Deschutes Valley because of its dark color and symmetry.[8] Part of theCascade volcanic arc in the northwestern United States, it lies within arain shadow[4] about 6.2 miles (10 km) to the east of the major mountain range.[10] In the High Cascades, theequilibrium line altitudes for valleyglaciers follow a gradient of about 74 feet per mile (14 m/km), which is significantly steeper than the gradient for the Western Cascades. Moving east, precipitation decreases across the Cascade arc; the gradient is even steeper east of the major crest at Black Butte, where the gradient is more than 200 feet per mile (38 m/km).[10] W. E. Scott argues that the volcano displays no evidence of glaciation.[10]
Black Butte lies just south of theMetolius Springs,[6] which lie in the southwestern corner of Jefferson County.[11] Accessible by roads branching off U.S. Route 20, the springs are located about 30 miles (48 km) northwest of the cities ofBend andRedmond.[11] Black Butte rises above the surrounding Metolius Valley, which has a width of about 3 miles (4.8 km) and an elevation above sea level of 3,000 feet (910 m).[11] At the volcano's northern base lie two openings spaced about 200 yards (180 m) apart, which give rise to the Metolius Springs. Bubbling out at a temperature of 48 °F (9 °C), the springs merge to form theheadwaters of theMetolius River, generating a total flow of 45,000 to 50,000 US gallons per minute (170,000 to 190,000 L/min) over the course of each year.[6] The river runs for 35 miles (56 km) to the north and east before reaching theDeschutes River, picking up 600,000 US gallons (2,300,000 L) along the way from other springs andtributaries along the eastern Cascade Range.[6] As glaciers advanced and retreated andsnow fields formed over time, they caused erosion, which was carried by streams associated with the Metolius River to spread across the river valley's floor.[12]
The last of these glaciers existed until about 10,000 years ago, with their end points markedhummocks of debris. The glaciers formedglacial troughs, depositedmoraines, and moved sand and gravel along withvolcanic ash andcinders to cover the Metolius Valley floor.[13] Black Butte lies about 5 miles (8.0 km) east–southeast ofSuttle Lake,[1] which occupies one of the local glacial troughs.[13]
Eruptions from Black Butte buried the ancestral Metolius River and leftboulders of lava in the area,[14] and Black Butte's formation dammed drainages for the Metolius, dividing the Metolius Valley into the northern segment where the river now runs and a southern portion that includes Black Butte Swamp, Glaze Meadow, and Indian Ford Creek. Black Butte Swamp and Glaze Meadow were likely formerly shallow lakes, though they now serve assumps for streams anddrainages from the Cascades,[15] which are located to the southwest.[16] Black Butte Swamp is a particularly important sump for extensive drainage from the southwest, its basin water lapping against Black Butte's southern base. Because it is elevated about 300 feet (91 m) above the Metolius Springs, the swamp acts as ahydraulic head for the spring water keeping the flow of the springs constant, and ensuring that there is a net influx of water into the swamp. Any excess water exits through Indian Ford Creek to flow east then south past the city of Sisters.[17] In modern times, the Metolius Valley consists ofglacial outwash, lava strata, and streamsediment, which together act as a sponge for snow and rain water percolating into the river basin.[13]
Black Butte lies east of the major crest of the Cascades, which is more arid compared to the Western Cascades.[18] Two forest populations at Black Butte were analyzed in a 1975 study conducted by D. B. Zobel ofOregon State University. These forest areas includedponderosa pine and tree species intermediate togrand andwhite firs.[18] The study found that trees at Black Butte did not experience significantmoisture stress[19] and thatphotosynthesis rates during dry summer seasons were more reduced at tree sites in the Western Cascades compared to at Black Butte.[20] Black Butte was found to have a shortergrowing season and less favorable winter temperatures for photosynthesis at its forest sites than study areas in the Western Cascade Province.[20] Along the trail that runs up Black Butte, the forest is diverse, with yellow-bellied ponderosa pines,mixed conifers, andsubalpine vegetation.[21]
Black Butte is part of theDeschutes National Forest,[21][22] which covers close to 1,600,000 acres (6,500 km2) in central Oregon.[23] It is also part of the Metolius Black Butte Scenic area within the Metolius Conservation Area, which encompasses about 10,600 acres (43 km2)[24] and includes suitable habitat fornorthern goshawks.[25] The Metolius River passes throughold-growth[26] forests of ponderosa pine,[27] as well as forests ofDouglas fir andwestern larch.[26] Every May native plants andwildflowers appear, includingearly blue violets,larkspur,serviceberry,Sitka valerian, andwestern buttercups.[27] During the summer season, river trails more prominently display plant species likearrowleaf balsamroot,American brooklime,bigleaf lupine,Douglas's spirea,Indian paintbrush, andmonkeyflower plants.[27] On islands in the river, wildflowers occasionally grow after their seeds bloom after falling into the water and accumulating over time. The area is noted for a rare species ofPenstemon known asPenstemon peckii, a wildflower that appears in 7 different colors, which isendemic to the Sisters area.[27] Other plants within the Metolius Preserve includeincense cedar trees,nutka rose,ocean spray,snowberry, andvine maple trees.[26]
More than 80 species of bird inhabit the Metolius Preserve area such as thewhite-headed woodpecker. The area supports largemammals likeAmerican black bears,badgers,bobcats,beavers,deer,cougars,elk, andotters, as well as smaller mammals likenorthern flying squirrels,shrews, andvoles.[26]
In the Oregon segment of the Cascade Volcanoes that runs for 210 miles (340 km) south ofMount Hood, there are at least 1,054Quaternary volcanoes, which form avolcanic belt 16 to 31 miles (25 to 50 km) in width.[28] This volcanic belt extends up to 19 miles (30 km) to the north of the border withCalifornia, where Quaternary volcanic activity is interrupted by a 40-mile (64 km) gap up to the Quaternary volcanoes nearMount Shasta.[28] The Quaternary volcanoes within the Oregon Cascades are extremely dense, concentrated within an area of about 3,700 square miles (9,500 km2).[28] Rocks within the Metolius Springs area form part of the High Cascades province and include both volcanic andglaciofluvial deposits.[6]
Black Butte marks the edge of the Sistersfault zone, which includes about 50 known faults that extend southeast through the cities of Sisters and Bend. In total, the Sisters fault zone runs for 37 miles (60 km) in length, with its width varying between 3.1 to 9.3 miles (5 to 15 km).[29] Black Butte itself sits on a small fault that straddles thegraben, and its lava deposits have been displaced slightly by a fault on the northwestern side of the volcano.[5] To the north lies the Green Ridgefault scarp, which trends to north and rises about 2,000 feet (610 m) above the Metolius Valley.[6] The fault's steepescarpment contains exposed, alternating layers of basaltic andesite,breccia, andagglomerate fromshield volcanoes, which mark the oldest rocks in the area. They are ofPliocene age, overlyingdiatomite,pumice, andtuffaceoussandstone layers.[6]
Most of the volcanoes in the Oregon Cascades are eitherscoria cones, small shield volcanoes, orlava fields, though the segment contains a number ofbasaltic andesitestratovolcanoes such asMount McLoughlin.[7] Black Butte is one such stratovolcano[4] (also known as a composite volcano),[9] with amafic (rich inmagnesium andiron) composition.[7] It is anextinct volcano.[30]
Also composed of basaltic andesite,[28] the cone rises 3,076 feet (938 m) over the surrounding plateau. Black Butte is a striking feature just north ofUS Highway 20, which descends from the east flank of theCascades. It is nearly symmetrical[8] with a youthful profile,[9] though it is actually older than any other visible High Cascades volcano. Black Butte is well-preserved due to a lack of glaciation east of the major Cascade arc.[31] Black Butte has undergone milderosion,[5] with shallowravines on its slopes,[15] deepgullies on its sides, and rocks withweathering rinds.[9] Black Butte forms a steep-sidedvolcanic cone,[5] with an unexposedpyroclastic core[5] and nosummit crater.[9] It is one of the larger mafic volcanic cones in the Oregon Cascades,[32] with a volume of 2.4 cubic miles (10 km3).[7] Black Butte's composition is characteristic for the High Cascades, consisting of light to dark gray basaltic andesite rock with a fine to mediumgrain. The flanks of the volcano displayoutcrops of the lava, which are blocky and mixed with zones of breccia, suggesting the flows were slow-moving and were erupted from a central vent.[12]
The Sixmile Butte lava field, of Pleistocene age, consists of ten cinder cones between Black Butte andBlack Crater. These cones erupted basaltic andesite, which was deposited prior to theglacial advance at Suttle Lake.[33] The field encompasses about 25 square miles (65 km2).[34] Lava deposits from nearby Cache Mountain have a normal magnetic polarity, corresponding to a potassium–argon dating age of 0.9 ± 0.05 million years, suggesting they were produced during the Jaramillo normal polarity of the Matuyama period between 0.98 and 1.04 million years ago.[5] There is a chain of Pleistocene cinder cones east of the butte that trends from northwest to southeast, with other Pleistocene cinder cones located to the south.[4] There is also a mafic, well-preserved cinder cone above the Green Ridge fault zone, which produced a Pleistocene lava flow.[14]
A study by Sherrod and his associates usedpotassium–argon dating to trace samples from Black Butte to 1.43 ± 0.33 million years ago,[5] during theMatuyama Polarity Zone ofreversed magnetic polarity.[35] These dates superseded an earlier determination of 400,000 years, which was recognized as incorrect based on polarity magnetization of the lava;[5] according to Peterson and Groh, E. M. Taylor also communicated an age of about 500,000 years for Black Butte from K–Ar dating of its rock.[15]
Large-scaleblock faulting in the vicinity of the Metolius Springs could have coincided with the beginning of volcanic activity in the High Cascades,[6] which gradually progressed from building shield-shaped edifices to more violent eruptions.[12] Volcanism resumed after the Green Ridge fault scarp reached its maximum height and fault movement ceased, occurring along a fault within the graben in the Metolius Springs vicinity. These eruptions built up Black Butte, though their duration is not clear.[12] The magmas at Black Butte likely had to ascend through the Green Ridge fault.[14]
Sherrod and his associates described an ancient basaltic andesite deposit from the Pleistocene, which displays reverse polarity and is older than 0.78 million years. This deposit includes lava flows from Black Butte, which are slightly to moderatelyporphyritic in texture and exhibit 5–10 percentplagioclasephenocrysts, about 0.039 to 0.079 inches (1 to 2 mm) in length.[5] They also have 3–5 percentolivine phenocrysts, which are about 0.039 inches (1 mm) across.[5] Sherrod et al. also described two previously identified, reverse-polarized basaltic andesite lava deposits at Black Butte, with ages of 0.46 ± 0.30 and 0.48 ± 0.2 million years, respectively.[36] The volcano's last known eruption was during the Pleistocene.[4] However, some eruptive activity has continued in the High Cascades; there is one lava flow in theMcKenzie Pass area to the west of Black Butte, which is only 1,500 years old.[37]
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Black Butte was a familiar landmark to the Native Americans.Ella E. Clark records a traditional story of the butte told to her by two Native Americans living on theWarm Springs Reservation, which had been told to them by their grandfathers. According to this tale, the mountains of Central Oregon were once people: Black Butte was the wife of nearby Green Ridge. Mount Hood and Mount Adams quarreled over a woman, and would regularly cross theBridge of the Gods to fight.Coyote called the other mountains to come and help arbitrate the dispute. The mountains marched north, including Black Butte and Green Ridge. The trip tired Black Butte, and she stopped to rest at the head of the Metolius River; Green Mountain was annoyed that she had stopped, and laid down, pouting. Coyote decided he could wait no longer, and broke the Bridge of the Gods; this caused the mountains to remain where they had stopped.[38]
It is not known who gave Black Butte its modern name, though historical records show settlers calling the volcano by that name as early as 1855. Lieutenant H. L. Abbot, one of the engineers involved with thePacific Railroad Surveys, referred to the volcano as Pivot Mountain in a diary entry published in theOregon Historical Quarterly,[39] though he also used the name Black Butte in the Pacific Railroad SurveysReports.[8] During his work for the surveys, Abbot scouted railroad routes in the area surrounding Black Butte, ultimately concluding that a railroad could not be built over the Cascade Range near Mount Jefferson.[40]
The butte had afire lookout ground house,[41][42] which was built in 1979 out of wood,[43] though the butte has been used for fire detection since 1910.[30] Fire lookout staff used the station to cook and sleep before it was condemned in 2014 and burned down in 2016 by the United States Forest Service, who released a statement that it "was ineligible for preservation as a historical structure both in time and because of improvements made."[43] Lookouts still work at Black Butte during the fire season but use ayurt (a type of portable tent) instead.[43] There has been a whitecupola structure on the top of the butte since 1923 and a more modern fire lookout tower, 62-foot (19 m) tall, which was built in 1995; neither are accessible to visitors.[30]
The land around Black Butte and the Metolius Springs is managed by the United States Forest Service, which has constructed a parking lot, trail, and viewpoint for the area.[11] There are a number of famous fishing resorts and a popular recreation area nearby.[11]Black Butte Ranch, which lies inDeschutes County[44] within Deschutes National Forest,[45] is aresort community that encompasses 1,800 acres (7.3 km2) and offers recreational activities includinghorseback riding, biking, hiking,canoeing,kayaking, andpaddleboarding; during the winter, the resort activities includeNordic skiing andsnowshoeing.[46]
The Black Butte hiking trail runs for about 2 miles (3.2 km) from atrailhead up the butte.[21] Trees thin in the second mile of the hike.[21] The trailhead is particularly busy during the summer season with vehicles and hikers, though the hiking trail itself is for hikers only.[22] The hike is popular and not demanding, climbing about 1,600 feet (490 m) to the peak, whereThree Sisters, Mount Washington, and Mount Jefferson can be seen.[30]
