San Luis Hills

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San Luis Hills
Sierro del Ojito.JPG
Sierro del Ojito in the Fairy Hills section of the San Luis Hills
Highest point
Elevation 2,806 m (9,206 ft) [1]
Coordinates 37°10′0″N105°44′32″W / 37.16667°N 105.74222°W / 37.16667; -105.74222 Coordinates: 37°10′0″N105°44′32″W / 37.16667°N 105.74222°W / 37.16667; -105.74222 [2]
Dimensions
Area428 sq mi (1,110 km2) [3]
Geography
LocationSan Luis Valley
CountryUnited States
StateColorado

The San Luis Hills [2] are a group of small mountain ranges in Conejos and Costilla counties in the San Luis Valley in southern Colorado. [4] The individual mountain ranges that make up the San Luis Hills include the Fairy Hills, the Brownie Hills, the Piñon Hills, and the South Piñon Hills. The San Luis Hills' highest point is Flat Top, elevation 9,206 feet (2,806 meters) [1]

Contents

Geographical setting

Each of the separate mountain ranges includes flat-topped mesas and hills, and the ranges trend from the southwest to the northeast. [4] Because the individual hills rise from the floor of the San Luis Valley, which is about 7,500 feet (2,300 meters) in elevation, [5] they appear more as hills than mountains, despite rising to eight or nine thousand feet above sea level.

The Hills are all within the Sangre de Cristo National Heritage Area. [6]

Individual ranges

Fairy Hills

The Fairy Hills lie at 37°12′37″N105°45′14″W / 37.21028°N 105.75389°W / 37.21028; -105.75389 . [7] They are north of Colorado State Highway 142 and west of the Rio Grande in Conejos County.

Brownie Hills

The Brownie Hills lie at 37°12′39″N105°42′50″W / 37.21083°N 105.71389°W / 37.21083; -105.71389 . [8] They are north of Colorado State Highway 142 and east of the Rio Grande, in Costilla County.

Piñon Hills

The Piñon Hills lie at 37°07′50″N105°49′02″W / 37.13056°N 105.81722°W / 37.13056; -105.81722 . [9] They are south of Colorado State Highway 142 and west of the Rio Grande, in Conejos County.

South Piñon Hills

The South Piñon Hills lie at 37°04′17″N105°48′31″W / 37.07139°N 105.80861°W / 37.07139; -105.80861 . [10] As their name indicates, they are south of the Piñon Hills in Conejos County, and just north of the New Mexico border.

Geology

The Manassa Dike. Part of Flat Top is visible on the left. Manassa Dike.JPG
The Manassa Dike. Part of Flat Top is visible on the left.

The hills are the exposed parts of an intra-rift horst. They are capped by Miocene basalts of the Hinsdale Formation. [11] The basalt is underlain by Oligocene andesite and dacite volcanic deposits of the lower Conejos Formation. [4]

Recreation

The public lands in the San Luis Hills are not developed for recreation. However, some informal hiking trails exist, and mountain climbing and bouldering are possible, especially around the Manassa Dike on south side of Flat Top. [12]

Protected areas

The San Luis Hills Wilderness Study Area occupies a 10,883-acre (4,404-hectare) tract of land in the Piñon Hills. The wilderness study area was established in 1980 and is owned by the Bureau of Land Management. [13]

In 2016, the Western Rivers Conservancy got funding from the Conservation Alliance to purchase a 17,019-acre (6,887-hectare) tract in the Brownie Hills on both sides of the Rio Grande, some of it adjacent to or overlapping with the Rio Grande Natural Area. The plan is to transfer the land to Costilla County, which will manage it for wildlife habitat, agriculture, and public open space. [14]

Related Research Articles

San Luis Valley

The San Luis Valley is a region in south-central Colorado with a small portion overlapping into New Mexico. The Rio Grande with headwaters in the San Juan Mountains about seven miles east of Silverton, Colorado flows through the San Luis Valley and then south into New Mexico. It contains 6 counties and portions of 3 others. The San Luis Valley was ceded to the United States by Mexico following the Mexican–American War. Hispanic settlers began moving north and settling in the valley after the United States made a treaty with the Utes and established a fort. Prior to the Mexican war the Spanish and Mexican governments had reserved the valley to the Utes, their allies. During the 19th century Anglo settlers settled in the valley and engaged in mining, ranching, and irrigated agriculture. Today the valley has a diverse Anglo and Hispanic population.

Costilla County, Colorado County in Colorado, United States

Costilla County is a county located in the U.S. state of Colorado. As of the 2010 census, the population was 3,524. The county seat is San Luis, the oldest continuously occupied town in Colorado.

Alamosa County, Colorado County in Colorado, United States

Alamosa County is a county located in the U.S. state of Colorado. As of the 2010 census, the population was 15,445. The county seat is Alamosa. The county name is the Spanish language word for a "grove of cottonwood trees."

Antonito, Colorado Statutory Town in Colorado, United States

Antonito is a Statutory Town located in Conejos County, Colorado, United States. The town population was 781 at the 2010 United States Census.

Manassa, Colorado Statutory Town in Colorado, United States

The Town of Manassa is the Statutory Town that is the most populous municipality in Conejos County, Colorado, United States. The town population was 991 at the 2010 United States Census.

Blanca, Colorado Statutory Town in State of Colorado, United States

The Town of Blanca is a Statutory Town in Costilla County, Colorado, United States. The town population was 385 at the 2010 census.

San Luis, Colorado Statutory Town in State of Colorado, United States

The Town of San Luis is a statutory town that is the county seat and the most populous town of Costilla County, Colorado, United States. Formerly known as San Luis de la Culebra, San Luis is the oldest continuously occupied town in Colorado. The population was 629 at the 2010 census.

Conejos River

The Conejos River is a tributary of the Rio Grande, approximately 92.5 miles (148.9 km) long, in south-central Colorado in the United States. It drains a scenic area of the eastern San Juan Mountains west of the San Luis Valley.

Alamosa National Wildlife Refuge

The Alamosa National Wildlife Refuge is an 11,169-acre (4,520 ha) United States National Wildlife Refuge located in southern Colorado. The site is located in the San Luis Valley along the east side of the Rio Grande approximately 8 miles (13 km) southeast of Alamosa primarily in southeastern Alamosa County, although very small parts extend into northeastern Conejos and western Costilla counties. It is managed by the United States Fish and Wildlife Service jointly with the Baca and Monte Vista National Wildlife Refuges. It was established in 1962 as a haven for migratory birds and other wildlife.

Chama, Colorado Unincorporated community in State of Colorado, United States

Chama is an unincorporated community and U.S. Post Office in Costilla County, Colorado, United States. The ZIP Code of the Chama Post Office is 81126.

Garcia, Colorado Unincorporated community in Colorado, United States

Garcia is an unincorporated community located in Costilla County, Colorado, United States. The San Luis post office (Zip Code 81152) serves Garcia postal addresses.

San Pablo, Colorado Unincorporated community in Colorado, United States

San Pablo is an unincorporated community located in Costilla County, Colorado, United States. The San Luis post office (Zip Code 81152) serves San Pablo postal addresses.

Mesita, Colorado Unincorporated community in Colorado, United States

Mesita is an unincorporated community located in Costilla County, Colorado, United States. The San Luis post office (Zip Code 81152) serves Mesita postal addresses.

Lasauses, Colorado

Lasauses or Los Sauces is a populated place in Conejos County, Colorado, United States, on the west side of the Rio Grande.

Bountiful, Colorado

Bountiful is an unincorporated community in Conejos County, in the U.S. state of Colorado.

Rio San Antonio (Colorado–New Mexico)

Rio San Antonio is a tributary of the Conejos River in northern New Mexico and southern Colorado. Via the Conejos River, it is part of the upper Rio Grande system. The river is used extensively for irrigation in its lower course through the southern San Luis Valley.

Lake Alamosa

Lake Alamosa is a former lake in Colorado. It existed from the Pliocene to the middle Pleistocene in the San Luis Valley, fed by glacial meltwater from surrounding mountain ranges. Water levels waxed and waned with the glacial stages until at highstand the lake reached an elevation of 2,335 meters (7,661 ft) and probably a surface of over 4,000 square kilometers (1,500 sq mi), but only sparse remains of the former waterbody are visible today. The existence of the lake was postulated in the early 19th century and eventually proven in the early 20th century.

Servilleta Basalt

The Servilleta Basalt or Servilleta Formation is a geologic formation that underlies most of the Taos Plateau of northern New Mexico. It has a radiometric age of 3.6 to 4.5 million years, corresponding to the Pliocene epoch.

Hinsdale Formation A geologic formation in New Mexico

The Hinsdale Formation is a geologic formation exposed in southwestern Colorado and northern New Mexico. It has a radiometric age of 4.4 to 26.8 million years, corresponding to the Neogene period.

References

  1. 1 2 "Flat Top". Geographic Names Information System . United States Geological Survey. 13 October 1978. Retrieved 31 December 2020.
  2. 1 2 "San Luis Hills". Geographic Names Information System . United States Geological Survey. 13 October 1978. Retrieved 31 December 2020.
  3. Burroughs, Richard L. (1971). "Geology of the San Luis Hills, south-central Colorado". In James, H.L. (ed.). San Luis Basin (Colorado): New Mexico Geological Society 22nd Annual Fall Field Conference Guidebook. New Mexico Geological Society. pp. 277–287.
  4. 1 2 3 Thompson, Ren A.; Shroba, Ralph A.; Machette, Michael N.; Fridrich, Christopher J.; Brandt, Theodore R.; Cosca, Michael A. (2015). Geologic map of the Alamosa 30′ × 60′ quadrangle, South-Central Colorado (PDF) (Map). Scientific investigations map ; 3342. Reston, VA: U.S. Department of the Interior, U.S. Geological Survey. p. 2. Retrieved 2020-12-31.
  5. "San Luis Valley". Geographic Names Information System . United States Geological Survey. 2001-08-03. Retrieved 2021-01-01.
  6. "Geology". Sangre de Cristo National Heritage Area. Retrieved 2020-12-31.
  7. "Fairy Hills". Geographic Names Information System . United States Geological Survey. 13 October 1978. Retrieved 31 December 2020.
  8. "Brownie Hills". Geographic Names Information System . United States Geological Survey. 13 October 1978. Retrieved 31 December 2020.
  9. "Piñon Hills". Geographic Names Information System . United States Geological Survey. 13 October 1978. Retrieved 31 December 2020.
  10. "South Piñon Hills". Geographic Names Information System . United States Geological Survey. 13 October 1978. Retrieved 31 December 2020.
  11. "Assessment of the mineral potential of public lands located within proposed solar energy zones in Colorado" (PDF). U.S. Department of the Interior, Bureau of Land Management. July 2012. Retrieved 2020-12-31.
  12. Elison, Jeff (2020). "chapter 18: Rock climbing in the San Luis Valley: Penitente and beyond". In Beeton, Jared Maxwell; Saenz, Charles Nicholas; Waddell, Benjamin James (eds.). The geology, ecology, and human history of the San Luis Valley. Louisville, Colorado: University Press of Colorado. pp. 466–475. doi:10.5876/9781646420407.c018. ISBN   9781646420414.
  13. "San Luis Hills Wilderness Study Area". U.S. Department of the Interior, Bureau of Land Management. Retrieved 2020-12-31.
  14. "Where do you GOCO- April 2018 projects". Great Outdoors Colorado. 2018-05-16. Retrieved 2020-12-31.