La Sal Mountains
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The La Sal Mountains or La Sal Range are a mountain range located in
Grand Grand may refer to: People with the name * Grand (surname) * Grand L. Bush (born 1955), American actor * Grand Mixer DXT, American turntablist * Grand Puba (born 1966), American rapper Places * Grand, Oklahoma * Grand, Vosges, village and c ...
and San Juan counties in the U.S. state of
Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...
, along the border with
Colorado Colorado (, other variants) is a state in the Mountain states, Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the wes ...
. The range rises above and southeast of Moab 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 straight-line distance from the northernmost part of western Canada, to New Mexico ...
. The maximum elevation is at Mount Peale, 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 (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma o ...
s and subsequent erosion of the surrounding less-resistant sedimentary rocks. The most abundant igneous rocks are porphyritic, with
phenocrysts 300px, feldspathic phenocrysts. This granite, from the Switzerland">Swiss side of the Mont Blanc massif, has large white plagioclase phenocrysts, triclinic minerals that give trapezoid shapes when cut through). 1 euro coins, 1 euro coin (diameter ...
of
hornblende Hornblende is a complex 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 in igneous and metamorphic rock ...
and
plagioclase Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more pro ...
: these rocks are called
diorite Diorite ( ) is an 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 in composition between low-sili ...
in some accounts but
trachyte Trachyte () is an extrusive igneous rock composed mostly of alkali feldspar. It is usually light-colored and aphanitic (fine-grained), with minor amounts of mafic minerals, and is formed by the rapid cooling of lava enriched with silica and al ...
in at least one other source. Syenite, some containing the unusual mineral nosean, 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 apar ...
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 251.9 Mya. It is the last ...
to
Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
. The La Sal Mountains rise high over the surrounding Colorado Plateau. Two other ranges on the Plateau, the
Abajo Mountains The Abajo Mountains, sometimes referred to as the Blue Mountains, is 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 National ...
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 Henry ...
, formed around igneous intrusions of about the same age. Yet other nearby ranges, such as the Carrizo Mountains 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.


Peaks of the La Sal Mountains


See also

* Geyser Pass


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