Laramie Mountains
From Wikipedia, the free encyclopedia
The Laramie Mountains are a range of moderately high peaks on the eastern edge of the Rocky Mountains in the state of Wyoming in the United States. The range is the northernmost extension of the line of the ranges along the eastern side of the Rockies, an in particular of the higher peaks of the Front Range directly to the south. North of the range, the gap between the Laramies and the Bighorn Mountains provided the route for historical trails, such as the Oregon Trail, the Mormon Trail, and the Pony Express.
The mountains extend northward from southeastern Wyoming between Cheyenne and Laramie, to Casper. They are named after the Laramie River, which cuts through the range from southwest to northeast and joins the North Platte River east of the range in eastern Wyoming. The mountains in turn give their name to the Laramide orogeny, the uplift of the of North American Plate approximately 70 million years ago that created the present Rocky Mountains.
The mountains consist of a series of Precambrian Sherman granite monadnocks rising above a broad erosion surface [1, 2] that form extensive unwooded parks whose surfaces are generally at about ca. 7000 ft (2135 m) above sea level. The high peaks of the range, which are much lower than those commonly associated with the Rocky Mountains, rise abruptly above the surrounding peneplain to altitudes between 8000 ft (2440m) and 9500 ft (2895m) above sea level, with the single exception of Laramie Peak which tops out at 10,274 ft (3130 m). The granitic soils were formed from the erosion of the surrounding monadnocks and have an effective depth of less than 12 inches (30 cm).
Three principal Life Zones are represented in the Laramies: Upper Sonoran, Transition and Canadian (sensu Carpenter [3]). Some early sources indicated that the Hudsonian Zone occurs on Laramie Peak but there is nothing distinctive about either the flora or fauna on the top of this peak, for it consists of nothing but a large granite outcrop. For further discussion of the Life Zones of this area, see Porter (1962) [4] as well as Cary [5]. On the E and NE slopes of the Laramies the prairie/mountain transition is very gentle at the south end (between Cheyenne and Laramie) and much more abrupt and broken farther north [6]. The elevation ranges from about ca. 4500' (1370 m) along the North Platte River to 10,274' (3130 m) at the top of Laramie Peak. On the western slopes the total relief is much less, as the floors of the three intermontane basins that border the Laramies on this side (Shirley, Hanna and Laramie basins) rarely drop below 7000'(2135m). An extensive high plain (7000-7900 ft/2135-2400 m) and semi-desert extends from the Laramie Mountains SW as far as the Shirley Mountains. The Laramie Basin separates the Laramie Mountains from the Medicine Bow Mountains to the S and W, and its floor is above 2135 m except for a few depressions and blowouts (e.g., Cooper Lake, 6980 ft, 2130m).
The Laramie Mountains are bisected by the Laramie River, which cuts a canyon through the mountains roughly due west of Wheatland, and then continues its generally eastward course to join the North Platte River near the town of Fort Laramie. The division marks the southern end of the continuous coniferous forest in the Laramies, and separates the range into two parts. The southern part is generally drier and much more open, with little or no forest except for the southern end at Pole Mountain and surrounding area, where the interesting granite outcrops at Vedauwoo provide climbing practice and grand picnic scenery.
The range is prominently visible from Interstate 25 between Casper and Cheyenne.
[edit] References
See Hardesty, Richard L. and Groothuis, Dennis R. Butterflies of the Laramie Mountains, Wyoming (Lepidoptera: Rhopalocera.) The introduction provides additional information on the Laramie Mountains. A PDF version of this may be downloaded [1].
1. Marshall, K. & Colbert, E. H. 1965. Stratigraphy and Life History. J. Wiley & Sons, NY.
2. Dunbar, C. O. 1960. Historical Geology. J. Wiley & Sons, NY. 2nd Ed., fig. 308.
3. Carpenter, J. R. 1956. An Ecological Glossary. Hafner, NY.
4. Porter, C. L. 1962. A flora of Wyoming. Part I. Bulletin of the University of Wyoming Agricultural Experimental Station. 402.
5. Cary, M., 1917. Life zone investigations in Wyoming. Bulletin USDA Biological Survey. 42: 1-95.
6. Blackstone, D. L. 1971. Traveler's guide to the geology of Wyoming. Bulletin of the Geological Survey of Wyoming. 55:1-90.
