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San Rafael Swell
From Wikipedia, the free encyclopedia
The San Rafael Swell is a large geologic feature located in south-central Utah, USA about 30 miles (50 km) west of Green River, Utah. The San Rafael Swell, approximately 75 miles by 40 miles (120 x 65 km), consists of a giant dome-shaped anticline of sandstone, shale, and limestone that was pushed up millions of years ago. Since that time, infrequent but powerful flash floods have eroded the sedimentary rocks into numerous valleys, canyons, gorges, mesas and buttes. The Swell is part of the Colorado Plateau physiographic region.
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Interstate 70 divides the Swell into northern and southern sections, and provides the only paved road access to the region. The swell lies almost entirely within Emery County.
The northern Swell is drained by the San Rafael River, while the southern Swell is drained by a number of small creeks which eventually join the Dirty Devil River in Hanksville, Utah. The Dirty Devil River is a tributary of the Colorado River, while the San Rafael River joins the Green River before it also flows into the Colorado. Muddy Creek cuts into the western edge of the Swell, exits at Muddy Creek Gorge, and then flows into the Fremont River.
The San Rafael Swell was formed when deeply buried Precambrian rocks faulted, or broke, during the Laramide orogeny, about 60 million years ago. These "basement" rocks below the present-day Swell moved upwards relative to the surrounding areas and caused the overlying sedimentary rocks to fold into a dome-like shape called an anticline. The resulting structure is analogous to a series of blankets draped over a box.
Since that time, the relentless force of running water has eroded the geologic layers, resulting in older rocks becoming exposed in the middle of the Swell, and younger rocks exposed around the edges. Many of the most impressive landforms are composed of more resistant rocks, including the Jurassic Navajo Sandstone, Triassic Wingate Sandstone, and Permian Coconino Sandstone. The folding is much steeper on the eastern edge of the Swell than in the west, and this eastern edge is referred to as the San Rafael Reef.
Evidence of Native American cultures, including the Fremont, Paiute, and Ute, is common throughout the San Rafael Swell in the form of pictograph and petroglyph panels. From about 1776 to the mid-1850's the Old Spanish Trail trade route passed through (or just north of) the Swell. In the past 150 years, areas of the Swell have been used for the grazing of sheep and cattle, as well as for uranium mining. Although surrounded by the communities of Price, Green River, Hanksville, Ferron, Castle Dale, and Huntington, the Swell itself does not support permanent residents.
The area is managed by the U.S. Bureau of Land Management, although the Swell does not currently enjoy special protection. Thus, rules regarding land use are less strict than in a National Park or wilderness area, and cattle grazing is allowed. In 2002, then-governor Mike Leavitt of Utah proposed the creation of a San Rafael Swell National Monument. President George Bush, who has authority to create such a National Monument under the Antiquities Act, has yet to act on Leavitt's proposal as of 2006.
The San Rafael Swell attracts hikers, backpackers, horseback riders, and all-terrain vehicle (ATV) enthusiasts. Many steep, narrow slot canyons popular with technical canyoneers are found in the San Rafael Reef. The use of ATVs in the Swell is controversial, as environmentalists draw attention to the fact that off-road vehicles damage the fragile desert cryptobiotic soils.
Goblin Valley State Park is on the southeastern edge of the San Rafael Swell.
- Allen, Steve, Canyoneering: The San Rafael Swell, 1992. ISBN 0-87480-372-1
- Kelsey, Michael R. Hiking and Exploring Utah's San Rafael Swell, 3rd edition, 1999. ISBN 0-944510-17-5
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