The La Sal Mountains or La Sal Range is a mountain range located in

Grand Grand may refer to: People with the name * Grand (surname) * Grand L. Bush (born 1955), American actor Places * Grand, Oklahoma, USA * Grand, Vosges, village and commune in France with Gallo-Roman amphitheatre * Grand County (disambiguation), ...

and

San Juan San Juan, Spanish for Saint John (disambiguation), Saint John, most commonly refers to: * San Juan, Puerto Rico * San Juan, Argentina * San Juan, Metro Manila, a highly urbanized city in the Philippines San Juan may also refer to: Places Arge ...

counties in the U.S. state of

Utah Utah is a landlocked state in the Mountain states, Mountain West subregion of the Western United States. It is one of the Four Corners states, sharing a border with Arizona, Colorado, and New Mexico. It also borders Wyoming to the northea ...

, along the border with

Colorado Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...

. The range rises above and southeast of

Moab Moab () was an ancient Levant, Levantine kingdom whose territory is today located in southern Jordan. The land is mountainous and lies alongside much of the eastern shore of the Dead Sea. The existence of the Kingdom of Moab is attested to by ...

and north of the town of La Sal. This range is part of the Manti-La Sal National Forest and the southern

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 ...

. The maximum elevation is at

Mount Peale Mount Peale is the highest point in the La Sal Range, La Sal Mountains of San Juan County, Utah, San Juan County, in the southeastern part of Utah, United States. It is also the highest point in Utah outside the Uinta Mountains. It is located ab ...

, reaching above sea level. The range contains three clusters of peaks separated by passes. The peaks span a distance of about . The name of the range dates to Spanish times, when the Sierra La Sal (meaning the "Salt Mountains") was a prominent landmark on the Old Spanish Trail between Santa Fe and Los Angeles.

Geology

The range formed due to intrusion of

igneous rock Igneous rock ( ), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial ...

s and subsequent erosion of the surrounding less-resistant sedimentary rocks. The most abundant igneous rocks are

porphyritic Porphyritic is an adjective used in geology to describe igneous rocks with a distinct difference in the size of mineral crystals, with the larger crystals known as phenocrysts. Both extrusive and intrusive rocks can be porphyritic, meaning ...

, with

phenocrysts 300px, Swiss side of the Mont Blanc massif, has large white phenocrysts of plagioclase (that have trapezoid shapes when cut through). 1 euro coin (diameter 2.3 cm) for scale. A phenocryst is an early forming, relatively large and usually conspic ...

hornblende Hornblende is a complex silicate minerals#Inosilicates, inosilicate series of minerals. It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole. Hornblende minerals are common ...

and

plagioclase Plagioclase ( ) is a series of Silicate minerals#Tectosilicates, tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continu ...

: these rocks are called

diorite Diorite ( ) is an intrusive rock, intrusive igneous rock formed by the slow cooling underground of magma (molten rock) that has a moderate content of silica and a relatively low content of alkali metals. It is Intermediate composition, inter ...

in some accounts, but

trachyte Trachyte () is an extrusive igneous rock composed mostly of alkali feldspar. It is usually light-colored and aphanite, aphanitic (fine-grained), with minor amounts of mafic minerals, and is formed by the rapid cooling of lava (or shallow intrus ...

in at least one other source.

Syenite Syenite is a coarse-grained intrusive igneous rock with a general composition similar to that of granite, but deficient in quartz, which, if present at all, occurs in relatively small concentrations (< 5%). It is considered a nosean Nosean, also known as noselite, is a mineral of the feldspathoid group with formula: . It forms isometric crystals of variable color: white, grey, blue, green, to brown. It has a Mohs hardness of 5.5 to 6 and a specific gravity of 2.3 to 2.4. It ...

, makes up a few percent of the igneous rocks present. Some igneous intrusions have the shapes of

laccolith A laccolith is a body of intrusive rock with a dome-shaped upper surface and a level base, fed by a conduit from below. A laccolith forms when magma (molten rock) rising through the Earth's crust begins to spread out horizontally, prying apart ...

s. The ages of these igneous rocks fall between 25 and 28 million years. The magmas were emplaced into sedimentary rocks with ages from

Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

. The La Sal Mountains rise high over the surrounding

Colorado Plateau The Colorado Plateau is a physiographic and desert region of the Intermontane Plateaus, roughly centered on the Four Corners region of the Southwestern United States. This plateau covers an area of 336,700 km2 (130,000 mi2) within w ...

. Two other ranges on the Plateau, the

Abajo Mountains The Abajo Mountains, sometimes referred to as the Blue Mountains, are a small mountain range west of Monticello, Utah, south of Canyonlands National Park and north of Blanding, Utah. The mountain range is located within the Manti–La Sal Natio ...

and the

Henry Mountains The Henry Mountains is a mountain range located in the southeastern portion of the U.S. state of Utah that runs in a generally north-south direction, extending over a distance of about . They were named by Almon Thompson in honor of Joseph Henr ...

, formed around igneous intrusions of about the same age. Yet other nearby ranges, such as the

Carrizo Mountains The Carrizo Mountains (36°50' N, 109°7'W) is a small, mostly circular mountain range 15 to 20 km (9 to 12 miles) in diameter located on the Colorado Plateau in northeastern Arizona. The range is about southwest of the Four Corners. The hig ...

and

Ute Mountain Ute Mountain, also known as Ute Peak or Sleeping Ute Mountain (; Ute: ''Wisuv Káruv'', Navajo: ''Dził Naajiní''), is a peak within the Ute Mountains, a small mountain range in the southwestern corner of Colorado. It is on the northern edge o ...

, formed about otherwise similar intrusions emplaced about 70 million years ago. The formation of these igneous rocks in two distinct time intervals has attracted the interest of scientists seeking explanations for magma production below relatively stable parts of the Earth's crust. Image:LaSalMountains.jpg, The La Sals at Sunset from Gemini Bridges Road File:Utah La Sal loop road in winter.jpg, View of Horse Mountain in winter, looking to the east on La Sal Loop Road, in Pinhook Valley, Utah Image:Arches8.jpg, View of the La Sal mountains from the entrance to

Arches National Park Arches National Park is a List of national parks of the United States, national park of the United States in eastern Utah. The park is adjacent to the Colorado River, north of Moab, Utah. The park contains more than 2,000 natural arch, natural ...

Image:A bare peak of La Sal.jpg, Little Tuk (left) and Mt. Tukuhnikivatz (right) of the La Sal Range in summer, seen from the south.

Peaks of the La Sal Mountains

References

Jules D. Friedman and A. Curtis Huffman Jr., Coordinators, ''Laccolith Complexes of Southeastern Utah: Time of Emplacement and Tectonic Setting—Workshop Proceedings,'' United States Geological Survey Bulletin 2158, 292 pages, 1998. http://pubs.usgs.gov/bul/b2158/B2158.pdf

External links

Manti La Sal National Forest
{{Authority control Colorado Plateau Laccoliths Mountains of Grand County, Utah Mountains of San Juan County, Utah Mountain ranges of Utah Ranges of the Rocky Mountains Manti-La Sal National Forest

Geology

Peaks of the La Sal Mountains

See also

References

Further reading

External links