Black Crater

Black Crater is a shield volcano in the Western Cascades in Deschutes County, Oregon. Located near McKenzie Pass, the volcano has a broad conical shape with gentle slopes. The volcano likely formed during the Pleistocene and has not been active within the last 50,000 years. Eruptive activity at the volcano produced mafic lava flows made of basaltic andesite and olivine basalt; it also formed a number of cinder cones. A normal fault occurs on the western side of the volcano, trending north–south. The volcano has been eroded by glaciers, which carved a large cirque into the northeastern flank of the mountain, forming its current crater.

The area was settled c. 1862, when pioneers moved to the forested region south of Black Crater, near what is now the city of Sisters. The volcano is part of the Three Sisters Wilderness, which offers recreational activities. The Black Crater Trail runs one way for from a trailhead on Oregon Route 242, and the southeastern part of the trail can be skied. Some Arctic–alpine plants can be found on the volcano, including mountain hemlock, ponderosa pine, bitterbrush, and Pacific silver fir.

Geography

Black Crater lies in Deschutes County,Template:Sfn southeast of Belknap Crater and northwest of Trout Creek Butte. Part of the Western Cascades,Template:Sfn it is in the McKenzie Pass region and close to the Willamette National Forest.Template:Sfn The Western Cascades consist of highly eroded layers of volcanic rock that drain into streams fed by runoff. These streams supply the Willamette River basin, and during the winter season the flow is increased by rain and melting snow.Template:Sfn

The volcano has an elevation of according to the U.S. National Geodetic Survey, which has a station just below the volcano's summit. The volcano has a broad conical shape with gentle slopesTemplate:Sfn and a diameter of about .Template:Sfn Its relief is about .Template:Sfn

Glaciers carved a cirque into the northeastern flank of the mountain, which forms its current crater. Glacial erosion has exposed the interior of the volcanic cone, but because of the volcano's relatively lower elevation and longer-lasting eruptive activity, it is less eroded than most other nearby volcanoes.Template:SfnTemplate:Sfn Glaciers likely moved between cinder cones on Black Crater but did not erode them.Template:Sfn

Black Crater is part of the Three Sisters Wilderness, which covers an area of and is therefore the second-largest wilderness area in Oregon. Designated by the United States Congress in 1964, the wilderness area borders the Mount Washington Wilderness to the north and shares its southern edge with the Waldo Lake Wilderness. The area includes of trails and many forests, lakes, waterfalls, and streams, including the source of Whychus Creek. Black Crater sits at the northern edge of the wilderness,Template:Sfn forming part of the Alpine Crest region. This area incorporates the northeastern third of the Three Sisters Wilderness and includes most of its major mountains as well as its most popularly visited glaciers, lakes, and meadows.Template:Sfn

Ecology and environment

Annual precipitation in the Oregon Cascades ranges from each year, with persistent but low-intensity rainfall. The wet climate supports rapid regeneration of vegetation, but the soil infiltration capacity is not surpassed even after fires.Template:Sfn Black Crater lies at the border of this climate and the one found to the immediate east, where annual precipitation is less than .Template:Sfn Its soil consists of andisols with fine-grained loam and tephra ejected from nearby volcanoes.Template:Sfn

Some Arctic–alpine plants can be found in the area around Black Crater above the timberline.Template:Sfn The north side of Black Crater has thick stands of mountain hemlock, while the eastern side supports ponderosa pine and bitterbrush. On the western side, there is forest with mountain hemlock and Pacific silver fir.Template:Sfn

On June 20, 2018, a debris flow coursed down the volcano, spurred on by runoff from a storm and secondary to the Milli Fire, which burned of forest land one year prior.Template:Sfn The flow started in an area with rilling and erosion near the upper volcanoTemplate:Sfn and traveled down the volcano's northwestern slope,Template:Sfn crossing Oregon Route 242 at two points.Template:Sfn The fire had burned 63% of the debris flow area at moderate or high severity.Template:Sfn At its narrowest point, the flow was , with depths exceeding .Template:Sfn

Geology

File:JuandeFucasubduction.jpg

Volcanism in the Cascade Range results from the subduction of the oceanic Juan de Fuca tectonic plate under the North American tectonic plate

The Cascade Range resulted from the subduction of the Juan de Fuca tectonic plate under the North American tectonic plate, with the High Cascade subprovince in central Oregon forming about east of the convergent boundary.Template:Sfn In the Oregon segment of the Cascade Volcanoes that runs for south of Mount Hood, there are at least 1,054 Quaternary volcanoes, which form a volcanic belt in width.Template:Sfn This volcanic belt extends up to to the north of the border with California, where Quaternary volcanic activity is interrupted by a gap up to the Quaternary volcanoes near Mount Shasta.Template:Sfn The Quaternary volcanoes within the Oregon Cascades are extremely dense, concentrated within an area of about .Template:Sfn Black Crater forms part of a chain of Pleistocene, northward-trending volcanic activity characterized by scoria cones, lava flows, and agglutinates. Some of this eruptive activity covered North Sister. The chain stretches for about from Black Crater to North Sister.Template:Sfn Black Crater sits above the Oregon High Cascades volcanic plateau.Template:Sfn

Black Crater is a shield volcano,Template:SfnTemplate:SfnTemplate:Refn composed of maficTemplate:SfnTemplate:Sfn basaltic andesiteTemplate:SfnTemplate:Sfn and olivine basalt.Template:Sfn It is part of a group of mafic shield volcanoes in central Oregon that also includes North Sister, Mount Washington, Broken Top,Template:Sfn and Black Butte.Template:Sfn Black Crater shows high amplitude positive polarity on magnetic anomaly maps, as do Mount Washington, Three Fingered Jack, and Mount Jefferson, suggesting an age of less than 730,000 years.Template:Sfn The volcano was likely formed in the late Pleistocene and has not erupted for about 50,000 years.Template:Sfn Near the end of its eruptive activity, the volcano formed cinder cones on its southwestern side and a parasitic lava cone near its western base. Scoria and agglomerate near the summit vent was likely erupted at the same time as these formations and have been intruded by dikes.Template:Sfn Later, additional cinder cones formed on the volcano, including one at the southern base known as Millican Crater,Template:Sfn which erupted basalt.Template:Sfn Millican Crater runs up against Black Crater, with a width of . It erupted a lava flow with dimensions of , which runs south and east and has been moderately eroded by glaciers. This lava flow is made of scoria and agglutinate.Template:Sfn

File:Black Crater Summit - looking south to Three Sisters (4103933426).jpg

The summit of Black Crater, with the Three Sisters in the background

Cinder cones also occur at and above the northern and northeastern flanks, respectively; they are well-preserved without current glaciers but show some evidence of weathering.Template:Sfn A crater on the northwestern slope is named Latta Crater after John Latta, an early settler in the region.Template:Sfn The two Matthieu Lakes (located on the southern side of the volcano near its summit) are named after the French Canadian pioneer François X. Matthieu, another early settler in Oregon.Template:Sfn Lava deposits from Black Crater are slightly porphyritic; they consist of sparse plagioclase and clinopyroxene and contain 55 to 57 percent silica.Template:SfnTemplate:Sfn The volcano produced a lava flow that reaches north and northeast of the summit for about . This lava extends from a central volcanic plug made of microdiorite. Due to the erosion, lava has irregular joints.Template:Sfn

A normal fault occurs on the western side of the volcano, trending north–south.Template:Sfn A fault scarp runs along the northern side of the volcanoTemplate:Sfn to the south, corresponding to an eruption at the Matthieu Lake fissure that occurred about 15,000 years ago, independent of Black Crater. The eruption was fed by a dike that could have reached the surface by the fault.Template:Sfn The Matthieu Lake fissure runs for about , trending north–east from north of North Sister until Black Crater. Made of basaltic andesite and andesite with silica content ranging from 53.5 to 60%,Template:Sfn the fissure sees increasing crystallization of its products moving south with decreasing amounts of crystals and phenocrysts.Template:Sfn The fissure consists of cinder cones and agglutinated volcanic vents that erupted cinders, volcanic bombs, and thick lava flows. The fissure has been covered by glaciers.Template:Sfn

Nearby features

The promontory Windy Point, which is made up of basaltic andesite lava and cinder, sits at the northwestern base of Black Crater. From there, Mount Washington can be seen, as well as basaltic andesite lava from the Yapoah cinder cone volcano and a lava field produced by Belknap Crater.Template:Sfn Belknap also erupted a heavy deposit of ash and scoria that covered the area between Black Crater and Dry Creek to the north.Template:Sfn The Sixmile Butte lava field, which formed during the Pleistocene, consists of ten cinder cones between Black Crater and Black Butte. These cones erupted basaltic andesite, which was deposited prior to the glacial advance at Suttle Lake.Template:Sfn The field encompasses about .Template:Sfn Southwest of Black Crater in Lane County, there is a small crater called Harlow Crater, named after M.H. Harlow, former President of the McKenzie toll road.Template:Sfn

Human history

Following cattle droving into the McKenzie Pass area in 1859 by missionaries and the discovery of gold in eastern Oregon in the early 1860s, the area south of McKenzie Pass was settled around 1862.Template:Sfn The settlers arrived with wagons and more than 60 oxen and 700 cattle.They moved into the forested region south of Black Crater, near what is now the city of Sisters. The group was led by the Scott brothers, who then created the McKenzie Fork Wagon Road Company to build a road over the lava fields in the area, followed by the McKenzie River Wagon Road Company, which was formed to build a road across the Cascade Range in the vicinity of the Three Sisters volcanoes that would cross the Deschutes River. A third construction company proposed the construction of a road north of the Three Sisters that would cross the Deschutes above the mouth of its tributary, Crooked River.Template:Sfn

Recreation

File:Black Crater trail (4103933114).jpg

A hiker on the Black Crater trail

The Black Crater Trail runs one-way for from a trailhead on Oregon Route 242. It passes through the Three Sisters Wilderness and eventually reaches the summit of Black Crater, where the North Sister and Mount Washington volcanoes can be seen. The trail can be hiked or attempted on horseback, but mountain bikes and motorized vehicles are not permitted. Considered to be of intermediate difficulty for hiking, it takes on average about 4 hours to complete, ranging in elevation from .Template:Sfn The southeastern portion of the trail can be skied.Template:Sfn Since 1905, All recreational activity at Black Crater has been overseen by the United States Forest Service. Forest rangers built a fire lookout tower in 1925, but it was out of service by the 1960s.Template:Sfn

Sources

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