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27-724: The relationships with other features is complex. At the BFZ's eastern end, near the Steens Mountain fault, the zone of surface faulting turns slightly to the south-southeast (possibly due to rotation of Nevada), then follows the Northern Nevada Rift to form the Oregon–;Nevada lineament, with a total length of over 75 km (47 mi). Lavas associated with the Nevada Rift have been dated to 16.3 Ma (millions of years ago), close to

54-501: A dwarf blue lupine , and Cusick's buckwheat ( Eriogonum cusickii ). Steens Mountain is distinctive in its absence of conifers , especially Ponderosa Pine and Douglas Fir , at elevations in which they would normally be found – from 5,500–8,000 feet (1,700–2,400 meters) above sea level. Although other mountains of the Great Basin also lack conifers, Steens Mountain is the largest mountain area without conifers. One possible cause of

81-401: A 425,000-acre (1,720 km ) area. This law protects 1,200,000 acres (1,870 sq mi; 4,860 km ) from mining, and 100,000 acres (156 sq mi; 405 km ) from cattle grazing. The west slope of Steens Mountain is traversed by a 52-mile (84 km) loop road, which is suitable for passenger vehicles. The road reaches an elevation of 9,700 feet (2,960 m), making it

108-652: A broad region, while the tail of the plume was overrun to make the Yellowstone Hotspot track. Age progressive volcanism along the Brothers Fault Zone (as well as the Steens Fault and North Nevada Rift) results from the expanding lithospheric melt opportunistically exploiting existing crustal faults. In summary, the Brothers Fault Zone, and the related Eugene–Denio, McLoughlin, and Vale zones, appear to be deep-seated structures in accreted terranes bounded by

135-852: A graben between two horsts – the Vosges mountains (in France ) and the Black Forest (in Germany ), and also the Rila – Rhodope Massif in Bulgaria , Southeast Europe , including the well defined horsts of Belasitsa (linear horst), Rila mountain (vaulted domed shaped horst) and Pirin mountain – a horst forming a massive anticline situated between the complex graben valleys of Struma and that of Mesta . Tilted type block mountains have one gently sloping side and one steep side with an exposed scarp, and are common in

162-465: A skull was unearthed in nearby Malheur Lake . In the 1970s, a wolverine was trapped and released on Steens Mountain. The mountain was called the "Snowy Mountains" by John Work , one of the fur traders who were the first Europeans in the area. It was renamed in 1860 for United States Army Major Enoch Steen , who fought and drove members of the Paiute tribe off the mountain. American Indians used

189-670: Is offset right-laterally about 10 to 20 km (6.2 to 12.4 mi) by the Eugene–;Denio fault zone, and another 15 to 20 km (9.3 to 12.4 mi) by the McLoughlin zone. At a possibly more fundamental level, the Brothers, Eugene–Denio, and McLoughlin zones, and possibly the Vale zone, all terminate near the Klamath – Blue Mountains Lineament (KBML; shortened and slightly misplaced on

216-498: Is the eruption of the 16.6 Ma Steens Basalts , the initial and most voluminous phase of the Columbia River Basalt Group lava flows that blanket eastern Oregon and the entire southeastern quarter of Washington. These also show a similar age progression to the north; there is a great deal of debate on how all of these are related, and how they initiated. The track of the Yellowstone Hotspot is neatly explained by motion of

243-538: The Alvord Desert at an elevation of about 4,200 feet (1,280 m) to 9,738 feet (2,968 m) at the summit. Steens Mountain is not part of a mountain range but is properly a single mountain, the largest of Oregon's fault-block mountains. The Steens Mountain Wilderness encompasses 170,166 acres (265.9 sq mi; 688.6 km ) of Steens Mountain. 98,859 acres (154.5 sq mi; 400.1 km ) of

270-571: The East African Rift zone. Death Valley in California is a smaller example. There are two main types of block mountains; uplifted blocks between two faults and tilted blocks mainly controlled by one fault. Lifted type block mountains have two steep sides exposing both sides scarps, leading to the horst and graben terrain seen in various parts of Europe including the Upper Rhine valley,

297-529: The BFZ also accommodates the offset with the Blue Mountains Province. It does this not by through-going strike-slip faulting (such as with the San Andreas Fault to the south) but by a series of hundreds of en echelon normal faults somewhat crosswise to the zone itself. Such faulting is believed to be the surface manifestation of a deeper shear zone. The Brothers Fault Zone is also the locus of

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324-563: The High Lava Plains (HLP) volcanism of central and southeastern Oregon. HLP volcanism is notable for showing an age progression from 16 Ma at its eastern end (near the Oregon–Nevada–Idaho corner) to the active Newberry Volcano at its western end. This age progression mirrors the very similar progression along the track of the Yellowstone Hotspot , which appears to have a common origin. Also closely related in space and time

351-603: The Klamath—Blue Mountains Lineament, which has been reactivated by Basin and Range extension, and exploited by mid-Miocene volcanism associated with the Yellowstone Hotspot. Steens Mountain Steens Mountain is a large fault-block mountain in the northwest United States , located in Harney County , Oregon . Stretching some fifty miles (80 km) north to south, on its west side it rises from

378-472: The North American craton over a plume ( hotspot ) of material rising from the mantle. But this explanation fails for the so-called "Newberry hotspot" track, which lies oblique to the motion of the craton. One suggestion is that the large blob of molten rock at the head of the plume was sheared off by the advancing edge of the craton, and remained entrained in front of the craton to melt the lithosphere in

405-600: The North American continent (such as the Klamath Mountains on the southern coast of Oregon, and Blue Mountains Province just north of the BFZ), the KBML has no apparent surface manifestation; it is believed to reflect a deeper structure, possible a pre-Tertiary continental margin. The BFZ is the northern edge of the Basin and Range Province, a region of northwest directed extension, wherefore

432-566: The Steens Mountain Wilderness varies greatly according to elevation. Common plants include sagebrush , juniper , various species of bunchgrass , mountain mahogany , aspen , mountain meadow knotweed , and false hellebore . Other vegetation endemic to Steens Mountain includes Steens paintbrush ( Castilleja pilosa var. steenensis ), moss gentian ( Gentiana fremontii ), Steens Mountain penstemon ( Penstemon davidsonii var. praeteritus ), Steens Mountain thistle ( Cirsium peckii ),

459-642: The Steens Mountain, particularly Big Indian Gorge. On October 24, 2000, President Bill Clinton approved the Steens Mountain Cooperative Management and Protective Act. The act was created by local landowners in cooperation with local and national government representatives in response to a proposed National Monument . This act created the Steens Mountain BLM Cooperative Management and Protection Area,

486-583: The Wilderness are protected from grazing and free of cattle . Steens Mountain is the remnant of a long shield volcano . The east face of Steens Mountain is composed mainly of basalts stacked one upon another. Lava flows several hundreds of feet thick inundated the region between 17 and 14 million years ago. Chemical data from magma deposits from the area reveal three distinct stages of volcanism. Layers of clay and volcanic dust show over forty lava flows on Steens Mountain. Most lava layers reach to 3,000 feet (910 m) thick or more in some areas. As

513-429: The absence of conifers is the isolation of Steens Mountain, although lack of seed dispersal by bird species such as Clark's Nutcracker may also be a factor. It is also possible that prehistoric fires, including fires used by Native Americans , eradicated the conifer population. Home to a wide variety of animals, the area is primarily known for birding , hunting, and fishing. Birds here include Golden eagles , owls, and

540-679: The base of Steens Mountain, including Alvord Hot Springs . Far from city lights, stargazing is also popular. Fault-block mountain Fault blocks are very large blocks of rock, sometimes hundreds of kilometres in extent, created by tectonic and localized stresses in Earth's crust . Large areas of bedrock are broken up into blocks by faults . Blocks are characterized by relatively uniform lithology . The largest of these fault blocks are called crustal blocks . Large crustal blocks broken off from tectonic plates are called terranes . Those terranes which are

567-431: The faults have a large vertical displacement. Adjacent raised blocks ( horsts ) and down-dropped blocks ( grabens ) can form high escarpments . Often the movement of these blocks is accompanied by tilting, due to compaction or stretching of the crust at that point. Fault-block mountains often result from rifting , an indicator of extensional tectonics . These can be small or form extensive rift valley systems, such as

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594-590: The full thickness of the lithosphere are called microplates. Continent-sized blocks are called variously microcontinents, continental ribbons, H-blocks, extensional allochthons and outer highs. Because most stresses relate to the tectonic activity of moving plates , most motion between blocks is horizontal, that is parallel to the Earth's crust by strike-slip faults . However vertical movement of blocks produces much more dramatic results. Landforms ( mountains , hills, ridges, lakes, valleys, etc.) are sometimes formed when

621-529: The highest road in Oregon. It is possible to drive nearly to the summit of the mountain and to other viewpoints such as Kiger Gorge. Steens Mountain is also host to Steens Mountain High Altitude Running Camp. Other recreational activities enjoyed on and around Steens Mountain are camping, picknicking, bicycling, hiking, hunting, sightseeing, soaring, and exploring. There are numerous hot springs along

648-628: The inception of basin-and-range faulting, but there is a suspicion that the rifting developed on an older strike-slip fault, possibly connected with the East Pacific Rise . At its west end, just past the Newberry Volcano , the BFZ terminates at the north-striking Sisters Fault, part of the High Cascades geological province. But further south the Pliocene (<5 Ma) High Cascades volcanic trend

675-621: The map at right). The KBML is a prominent, 700 km (430 mi) long southwest-to-northeast-striking gravitational anomaly that crosses all of Oregon. It coincides with the southern boundary of the Columbia Embayment (the Olympic–;Wallowa Lineament in Washington being the northern boundary), a region noticeably lacking in pre- Tertiary bedrock. Aside from aligning with the northwestern edge of several terranes that have accreted to

702-468: The protected sage grouse . Other animals found in the area include rattlesnakes , scorpions, elk , bighorn sheep , pronghorn antelope , and cougars . The area is home to wild horses . Drawing much controversy, the Bureau of Land Management engages in wild horse roundups every few years, employing helicopters to herd the horses. Historically, Steens Mountain Wilderness was once home to grizzly bears ;

729-446: The surface cracked, peaks and valleys were formed. Erosion and landfalls continue to modify the faces of the cliffs along the mountain. The sediment bedding is roughly horizontal, evidence to the absence of compressional forces . The white sediments consist primarily of stratified acidic tuffs. While rain hasn't been a main contributor to erosion , ice and snow melt are the main sources of erosion on Steens Mountain. Vegetation in

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