The Elkhorn Mountains are a

mountain range A mountain range or hill range is a series of mountains or hills arranged in a line and connected by high ground. A mountain system or mountain belt is a group of mountain ranges with similarity in form, structure, and alignment that have aris ...

in southwestern

Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...

, part of the

Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in great-circle distance, straight-line distance from the northernmost part of Western Can ...

and are roughly 300,000 acres (1200 km²) in size. It is an inactive volcanic mountain range with the highest point being Crow Peak at , right next to Elkhorn Peak, . The range is surrounded by the cities of

Helena Helena may refer to: People *Helena (given name), a given name (including a list of people and characters with the name) *Katri Helena (born 1945), Finnish singer * Saint Helena (disambiguation), this includes places Places Greece * Helena ...

, Montana City, Townsend,

Whitehall Whitehall is a road and area in the City of Westminster, Central London, England. The road forms the first part of the A roads in Zone 3 of the Great Britain numbering scheme, A3212 road from Trafalgar Square to Chelsea, London, Chelsea. It ...

, and

Boulder In geology, a boulder (or rarely bowlder) is a rock fragment with size greater than in diameter. Smaller pieces are called cobbles and pebbles. While a boulder may be small enough to move or roll manually, others are extremely massive. In ...

and is part of the

Helena National Forest Helena National Forest is located in west-central Montana, in the United States. Covering , the forest is broken into several separate sections. The eastern regions are dominated by the Big Belt Mountains, and are the location of the Gates of ...

in Montana's Jefferson County.

Geology

The rocks of the Elkhorns were formed about 74 to 81 million years ago (

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

time) as a result of the Farallon tectonic plate subducting beneath western North America and allowing

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

to rise to the surface. The Elkhorn Mountains Volcanics are

extrusive Extrusive rock refers to the mode of igneous volcanic rock formation in which hot magma from inside the Earth flows out (extrudes) onto the surface as lava or explodes violently into the atmosphere to fall back as pyroclastics or tuff. In contr ...

rocks related to the

plutonic Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form ''intrusions'', such as batholiths, dikes, sills, laccoliths, and volcanic necks.Intrusive RocksIntrusive rocks accessdate: Marc ...

granites of the

Boulder Batholith The Boulder Batholith is a relatively small batholith in southwestern Montana, United States, exposed at the surface as granite (more specifically quartz monzonite) and serving as the host rock for rich mineralized deposits at Butte and other loc ...

. Volcanic flows,

lahar A lahar (, from ) is a violent type of mudflow or debris flow composed of a slurry of Pyroclastic rock, pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a valley, river valley. Lahars are o ...

s, and ash falls from sources in the Elkhorn Mountains reach as far as

Choteau, Montana Choteau is a city in and the county seat of Teton County, Montana, United States. The population was 1,721 at the 2020 census. Choteau is named after French fur merchant, trader and explorer Pierre Chouteau, Jr., who is also the namesake of ...

, but the thickest deposits lie within a radius of about from the Elkhorns. The volcanics probably originally covered an area of about . Mineral deposits associated with the Elkhorn Mountains Volcanics include those mined at Elkhorn, Montana, now a ghost town, and gold at the Golden Sunlight Mine near

, which is associated with a breccia pipe in the volcanics. The mountain range seen today is related to regional structural uplift dating mostly to

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

time.

The Land

forest fire A wildfire, forest fire, or a bushfire is an unplanned and uncontrolled fire in an area of combustible vegetation. Depending on the type of vegetation present, a wildfire may be more specifically identified as a bushfire ( in Australia), dese ...

in 1988 burned 47,000 acres (190 km²) of the mountain range, leaving carpets of

seedling A seedling is a young sporophyte developing out of a plant embryo from a seed. Seedling development starts with germination of the seed. A typical young seedling consists of three main parts: the radicle (embryonic root), the hypocotyl (embry ...

s growing into new

lodgepole pine ''Pinus contorta'', with the common names lodgepole pine and shore pine, and also known as twisted pine, and contorta pine, is a common tree in western North America. It is common near the ocean shore and in dry montane forests to the subalpin ...

forests. The land has been used extensively in the past for

gold Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...

and

silver Silver is a chemical element; it has Symbol (chemistry), symbol Ag () and atomic number 47. A soft, whitish-gray, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. ...

mining Mining is the Resource extraction, extraction of valuable geological materials and minerals from the surface of the Earth. Mining is required to obtain most materials that cannot be grown through agriculture, agricultural processes, or feasib ...

logging Logging is the process of cutting, processing, and moving trees to a location for transport. It may include skidder, skidding, on-site processing, and loading of trees or trunk (botany), logs onto logging truck, trucksopen range In the Western United States and Canada, open range is rangeland where cattle roam freely regardless of land ownership. Where there are "open range" laws, those wanting to keep animals off their property must erect a fence to keep animals out; th ...

grazing, leaving a noticeable impact; most notably the abandoned

mining town A mining community, also known as a mining town or a mining camp, is a community that houses miners. Mining communities are usually created around a mine or a quarry. Historical mining communities Australia * Ballarat, Victoria * Bendig ...

of Elkhorn. Recently with efforts conducted by the BLM, Montana FWP and

, new conservation and

wildlife management Wildlife management is the management process influencing interactions among and between wildlife, its Habitat, habitats and people to achieve predefined impacts. Wildlife management can include wildlife conservation, population control, gamekeepi ...

plans have been put into place including

big horn sheep The bighorn sheep (''Ovis canadensis'') is a species of sheep native to North America. It is named for its large horns. A pair of horns may weigh up to ; the sheep typically weigh up to . Recent genetic testing indicates three distinct subspeci ...

reintroduction and the

westslope cutthroat trout The Westslope cutthroat trout (''Oncorhynchus lewisi'')Page, Lawrence M.; Bemis, Katherine E.; Espinosa-Pérez, Héctor S.; Findley, Lloyd T.; Gilbert, Carter R.; Hartel, Karsten E.; Lea, Robert N.; Mandrak, Nicholas E.; Neighbors, Margaret A. ( ...

restoration program. Management of the 2000+

elk The elk (: ''elk'' or ''elks''; ''Cervus canadensis'') or wapiti, is the second largest species within the deer family, Cervidae, and one of the largest terrestrial mammals in its native range of North America and Central and East Asia. ...

herd in the area and the suppression of

noxious weeds A noxious weed, harmful weed or injurious weed is a weed that has been designated by an agricultural or other governing authority as a plant that is harmful to agricultural or horticultural crops, natural habitats or ecosystems, or humans or lives ...

is also an ongoing task. Despite the impacts of mining, around 100,000 acres of the Elkhorns were still roadless in 1992; this included 85,000 acres of roadless National Forest land as well as adjacent BLM, state and private lands. Congress designated 175,000 acres of the range as the "Elkhorns Wildlife Management Area," and one of Montana's most productive elk herds inhabits the range. Because the Elkhorns are higher in elevation than the nearby section of the

Continental Divide A continental divide is a drainage divide on a continent such that the drainage basin on one side of the divide feeds into one ocean or sea, and the basin on the other side either feeds into a different ocean or sea, or else is endorheic, not ...

, they catch more moisture than do most other ranges east of the Divide. For this reason, the Elkhorns are especially diverse, with 148 documented vertebrate species.

Climate

Tizer Basin is a

SNOTEL 300px, Data from a SNOTEL site in Elko County, Nevada SNOTEL is an automated system of snowpack and related climate sensors operated by the Natural Resources Conservation Service (NRCS) of the United States Department of Agriculture in the Weste ...

weather station situated by Big Tizer Creek near Bullock Hill (Montana). , Tizer Basin has a

subalpine climate The subarctic climate (also called subpolar climate, or boreal climate) is a continental climate with long, cold (often very cold) winters, and short, warm to cool summers. It is found on large landmasses, often away from the moderating effects of ...

(

Köppen Köppen is a German surname. Notable people with the surname include: * Bernd Köppen (1951–2014), German pianist and composer * Carl Köppen (1833-1907), German military advisor in Meiji era Japan * Edlef Köppen (1893–1939), German author ...

''Dfc'').

Notes

External links

Geology of the Elkhorn Mountains VolcanicsElkhorn Wildlife Management Unit Elkhorn Mountain Endurance Runs
{{Authority control Mountain ranges of Montana Ranges of the Rocky Mountains Geology of Montana Landforms of Jefferson County, Montana Helena National Forest

Geology

The Land

Climate

See also

Notes

External links