La Sal Range

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La Sal mountain range as seen from Slickrock Trail in Moab, Utah.

The La Sal Range (or La Sal Mountains) is located in Grand and San Juan counties, near the eastern border of the state of Utah, and rising above the town of Moab. This range is part of the Manti-La Sal National Forest and the southern Rocky Mountains. The maximum elevation is at Mount Peale, reaching 12,721 feet (3,877 m) above sea level. The range contains three clusters of peaks separated by passes. The peaks span a distance of about 18 miles (25 km). The name of the range dates to Spanish times, when the Sierra La Sal (meaning the "Salt Mountains") were a prominent landmark on the Old Spanish Trail between Santa Fe and Los Angeles.

The range formed as a result of intrusion of igneous rocks and subsequent erosion of the surrounding less-resistant sedimentary rocks. The most abundant igneous rocks are porphyritic, with phenocrysts of hornblende and plagioclase: these rocks are called diorite in some accounts but trachyte in at least one other source. Syenite, some containing the unusual mineral nosean, makes up a few percent of the igneous rocks present. Some of the igneous intrusions have the shapes of laccoliths. Ages of these igneous rocks fall in the interval 25 to 28 million years. The magmas were emplaced into sedimentary rocks with ages from Permian to Cretaceous.

La Sal mountain range as seen from Arches National Park.

Mt. Tukuhnikivatz (left) and Mt. Peale (right) of the La Sal Range in summer, seen from the south.

Fall forest foliage of the La Sal mountains.

The La Sal Range rises high over the surrounding Colorado Plateau. Two other ranges on the Plateau, the Abajo Mountains and the Henry Mountains, formed around igneous intrusions of about the same age. Yet other nearby ranges, such as the Carrizo Mountains and Ute Mountain, formed about otherwise similar intrusions emplaced about 70 million years ago. 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.

Mountain ranges associated with laccoliths and other igneous intrusions on part of the Colorado Plateau. The red dot marks the Four Corners, the intersection of Utah, Colorado, New Mexico, and Arizona. L, La Sal Range; A, Abajo Mountains; S, (Sleeping) Ute Mountain; C, Carrizo Mountains; N, Navajo Mountain; H, Henry Mountains. Cropped, marked, and lower resolution from original image of NASA Visible Earth http://veimages.gsfc.nasa.gov//2883/4corners_2002160.jpg

[edit] Peaks of the La Sal Range

The significant peaks of the La Sal Range are:

Mount Peale - 12,721 feet (3877 m)
Mount Mellenthin - 12,645 feet (3854 m)
Mount Tukuhnikivatz - 12,482 feet (3805 m)
Mount Waas - 12,331 feet (3758 m)
Manns Peak - 12,272 feet (3741 m)
Mount Laurel - 12,271 feet (3740 m)
Mount Tomasaki - 12,239 feet (3730 m)
Pilot Mountain - 12,200 feet (3719 m)
Green Mountain - 12,163 feet (3707 m)
Little Tuk - 12,048 feet (3672 m)
Castle Peak - 12,044 feet (3671 m)
La Sal Peak - 12,001 feet (3658 m)

[edit] 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