The Trout Creek Mountains are a remote, semi-arid Great Basin mountain range mostly in southeastern Oregon and partially in northern Nevada in the United States. The range's highest point is Orevada View Benchmark, above sea level, in Nevada. Disaster Peak, elevation , is another prominent summit in the Nevada portion of the mountains.
The mountains are characteristic of the Great Basin's topography of mostly parallel mountain ranges alternating with flat valleys. Oriented generally north to south, the Trout Creek Mountains consist primarily of fault blocks of basalt, which came from an ancient volcano and other vents, on top of older metamorphic rocks. The southern end of the range, however, features many granitic outcrops. As a whole, the faulted terrain is dominated by rolling hills and ridges cut by escarpments and canyons.
Most of the range is public land administered by the federal Bureau of Land Management. There is very little human development in the remote region—cattle grazing and ranching are the primary human uses—but former mines at the McDermitt Caldera produced some of the largest amounts of mercury in North America in the 20th century. Public lands in the mountains are open to recreation but are rarely visited. Vegetation includes large swaths of big sagebrush in addition to desert grasses and cottonwood and alder stands. Sage grouse and mountain chickadee are two bird species native to the range, and common mammals include pronghorn and jackrabbits.
Despite the area's dry climate, a few year-round streams provide habitat for the rare Lahontan cutthroat trout. Fish populations in the Trout Creek Mountains declined throughout much of the 20th century. In the 1980s, the effects of grazing allotments on riparian zones and the fish led to land-use conflict. The Trout Creek Mountain Working Group was formed in 1988 to help resolve disagreements among livestock owners, environmentalists, government agencies, and other interested parties. The stakeholders met and agreed on changes to land-use practices, and since the early 1990s, riparian zones have begun to recover.
Geography
The Trout Creek Mountains are in a very remote area of southeastern Oregon and northern Nevada, in Harney and Humboldt counties. The nearest human settlements are the Whitehorse Ranch, about directly north from the middle of the mountains; Fields, Oregon, about to the northwest; Denio, Nevada, about to the west; and McDermitt, Nevada–Oregon, about to the east. The distances given are each measured in a straight line connecting two points. The mountains are about directly southwest of Boise, Idaho, and about northeast of Reno, Nevada.
The range and surrounding non-mountainous areas cover an area of . The mountains run north to south and east to west. More of the range is in Oregon (78%) than in Nevada (22%). The highest point in the range is Orevada View Benchmark, which is above sea level and is located in Nevada about one mile south of the Oregon border. About two miles southeast of Orevada View is Disaster Peak, "a large, symmetrical butte that is visible throughout the region." At , Disaster Peak anchors the southern end of the mountains in a sub-range called The Granites.
The Oregon Canyon Mountains border the Trout Creek Mountains on the east along the Harney–Malheur county line (according to the United States Geological Survey's definitions), while the Pueblo Mountains are the next range west of the Trout Creek Mountains. The Bilk Creek Mountains in both Oregon and Nevada border the Trout Creek Mountains on the southwest; the two ranges are separated by Log Cabin Creek and South Fork Cottonwood Creek. South of the Trout Creek Mountains is the Kings River Valley, which separates the Bilk Creek Mountains on the west from the Montana Mountains on the east.
The terrain in the Trout Creek Mountains varies from broad, flat basins and rolling ridges to high rock escarpments cut by deep canyons. The canyons have steep walls with loose talus slopes at the bottoms. There are meadows around springs in the mountains, although most streams in the range do not flow year-round. Major streams that flow off the north slopes of the mountains include (from west to east) Cottonwood Creek, Trout Creek, Willow Creek, and Whitehorse Creek. These streams all flow into endorheic basins in Harney County, Oregon. Trout Creek and Whitehorse Creek are the largest of the four. The Kings River and McDermitt Creek each drain an area on the south slopes of the Trout Creek Mountains. The Kings River begins in The Granites and flows south into Nevada, where it meets the Quinn River, which evaporates in the Black Rock Desert. McDermitt Creek begins in Oregon a few miles north of The Granites and flows generally east, crossing the Oregon–Nevada border five times before disappearing into the floor of the Quinn River Valley south of McDermitt.
Geology
The mountains lie within the Basin and Range Province of the Western United States, which is characterized by parallel fault blocks that form long north–south mountain ranges separated by wide, high-desert valleys. The Trout Creek Mountains are uplifted and tilted fault blocks with steep escarpments along the southern and eastern sides. The southern area of the range, known as The Granites, has numerous outcrops of Cretaceous granite beneath younger volcanic rocks.
The rocks themselves of the Trout Creek Mountains are primarily basalt from a shield volcano that once stood where Steens Mountain is today. About 17 million years ago, during the Miocene epoch, the Yellowstone hotspot was located beneath the thinning crust of southeastern Oregon and caused eruptions from Steens and nearby vents. The Steens eruptions lasted for about one million years and produced at least 70 separate basaltic lava flows. Subsequent faulting associated with the regional crustal thinning of the Basin and Range uplifted and tilted these rocks to shape them into the Trout Creek Mountains.
Beneath the mountains, underlying the basaltic rocks, are much older metamorphic rocks that may be related to some of the Triassic formations of the Blue Mountains in northeastern Oregon. Within these metamorphic rocks are diorite and granodiorite – intrusive bodies that presumably formed during the Cretaceous Period.
One broad geologic feature in the Trout Creek Mountains is McDermitt Caldera. The oval-shaped caldera is a collapsed lava dome that straddles the Oregon–Nevada border on the eastern side of the range south of the Oregon Canyon Mountains. It is about long and wide. The lava dome was created by volcanic eruptions in the early Miocene. A total of five large ash flows were produced along with a large rhyolite dome structure. The caldera formed when the dome collapsed about 16 million years ago. The caldera contains significant ore deposits, and mercury and uranium have been mined at eight or more sites in and around the caldera. Other sites at the caldera were mined for antimony, cesium, and lithium ores.
Climate The Trout Creek Mountains are semi-arid because they are in the eastern rain shadow of mountain ranges to the west. When moist air from the Pacific Ocean moves eastward over the Oregon and California coastal ranges and the Cascade Range, most precipitation falls in those mountains before reaching the Trout Creek Mountains. As a result, the average annual precipitation in the Trout Creek Mountains is only per year, with most areas receiving between annually. Much of the annual precipitation occurs between the beginning of March and the end of June. Most of the rest falls as snow during the fall and winter months. Snowpack at elevations below usually melts by April; however, at the higher elevations, snow can remain until mid-June. Local flooding often occurs in the spring as the snowpack melts.
The prevailing winds are from the west-southwest, and they are normally strongest in March and April. Brief, intense thunderstorms are common between April and October. Thunderstorms in the summer months tend to be more isolated and often produce dry lightning strikes.
Ecology
Flora
Vegetation in the Trout Creek Mountains is dominated by big sagebrush and desert grasses. Other common shrubs include bitterbrush, snowberry, and Ceanothus. There are also patches of mountain mahogany in some areas. Common grass species include Idaho fescue, bluebunch wheatgrass, cheatgrass, western needlegrass, Sandberg's bluegrass, Thurber's needlegrass, and bottlebrush squirreltail, as well as basin wildrye in some well-drained areas."Description of the Existing Environment", pp. 14–15
Less than one percent of the range consists of meadow wetlands and riparian greenways (vegetation along stream banks). However, these areas are vital to the local ecosystem. The meadows surround springs, which are mostly on gently sloping uplands or in stream bottoms, and range in size from about . Narrow riparian greenways follow the year-round streams. Many greenway areas have quaking aspen and willow groves. Cottonwood and alder groves can be found at lower elevations where terrain is flatter and stream channels are wider. Sedges and rushes are also native to these stream bottoms. Years of heavy livestock grazing in parts of the range resulted in the loss of some grass species, riparian vegetation, and young aspen and willow trees. Restoration of riparian areas began in the early 1970s, and plans to reduce grazing were implemented in the 1980s and early 1990s. However, large wildfires in southeastern Oregon during the summer of 2012 burned much of the range's vegetation, damaging riparian ecosystems and killing hundreds of grazing cattle.
Fauna
Animals in the Trout Creek Mountains are adapted to the environment of the High Desert. Pronghorn are common in the open, sagebrush-covered basins, while mule deer live in the cottonwood and willow groves. There are also bighorn sheep, cougars, and bobcats in the high country. Jackrabbits and coyotes are prevalent throughout the range. Mustangs sometimes pass through the mountains as they roam the Great Basin. Some other mammals include the northern pocket gopher, mountain cottontail, and Belding's ground squirrel. North American beavers live in and along streams, as do Pacific tree frogs, western spadefoot toads, and garter snakes."Description of the Existing Environment", p. 37 Native bird species include the sage grouse, mountain chickadee, gray-headed junco, black-throated gray warbler, Virginia's warbler, MacGillivray's warbler, pine siskin, red crossbill, bushtit, hermit thrush, northern goshawk, and species of raven and eagle.
Several streams in the Trout Creek Mountains are home to trout, including the rare Lahontan cutthroat trout subspecies. These include Willow Creek, Whitehorse Creek, Little Whitehorse Creek, Doolittle Creek, Fifteen Mile Creek, Indian Creek, Sage Canyon Creek, Line Canyon Creek, and some tributaries of McDermitt Creek. Lahontan cutthroat trout live in small, isolated populations that are often confined to individual streams, many of them in the Trout Creek Mountains. These populations have significant genetic differences due to their history of isolation. For most of the 20th century, the trout's numbers declined considerably. It was listed under federal law as an endangered species in 1970 and was reclassified as threatened in 1975. Reasons for the fish's decline included habitat degradation from cattle grazing, drought, overfishing, competition with other fish, and hybridization with introduced rainbow trout, which decreased the number of genetically pure Lahontan cutthroat trout. However, reductions in cattle grazing in riparian zones since the 1980s allowed fish habitat and populations to start to recover.
Human uses