- Henry Mountains
Geobox|Range
name=Henry Mountains
image_caption=Peaks in the Henry mountains viewed from a high mountain road
country=United States
state=Utah
parent=Rocky Mountains
border=
highest=Mount Ellen
highest_elevation_imperial=11522
highest_lat_d=38|highest_lat_m=6.53|highest_lat_s=|highest_lat_NS=N
highest_long_d=110|highest_long_m=48.82|highest_long_s=|highest_long_EW=W
geology=igneous| period=| orogeny=
area_imperial=
length_imperial=
length_orientation=
width_imperial=
width_orientation=
map_caption=Location of the Henry Mountains within UtahThe Henry Mountains are located in the southeastern portion of the U.S. state of
Utah and run in a generally north-south direction, extending over a distance of about 30 miles (50km). They were named byJohn Wesley Powell in honour ofJoseph Henry , the first secretary of theSmithsonian Institution . The nearest town of any size isHanksville, Utah , which is north of the mountains. The Henry Mountains were the last mountain range to be added to the map of the 48 contiguous U.S. states,cite web | last = Heath | first = Steven H. | title = A Historical Sketch of the Scientific Exploration of the Region Containing the Grand Staircase-Escalante National Monument | publisher = Bureau of Land Management Science Symposium | date = 1997 | url = http://www.ut.blm.gov/monument/science-symposium-1997/general01.html | accessdate = 2007-02-02 ] and before their official naming by Powell, were sometimes referred to as the "Unknown Mountains."Geography and Geology
The range is clustered into two main groups, with Highway 276 dividing the two portions. The northern group is by far the taller of the two with Mount Ellen: 11,506 feet above sea level;
Mount Pennell : 11,371 feet; andMount Hillers : 10,723 feet. The southern group is much lower in elevation. The southern group has two peaks: Mount Ellsworth: 8,235 feet andMount Holmes : 8,000 feet. The southern group is also known as the "Little Rockies".The Henry Mountains are drained by a number of canyon systems which radiate away from the isolated range, flowing north into the Fremont River, east into the
Dirty Devil River , or south intoLake Powell .The geology of these mountains was first studied in 1875-1876 by
Grove Karl Gilbert . He coined the term "laccolite" (nowlaccolith ) to describe the characteristic shapes of some of the igneous intrusions that core the mountains. The main type of igneous rock isporphyritic diorite .Ages of the igneous rocks are important for understanding the evolution of the
Colorado Plateau . Ages of these rocks were reported to be about 45 to 50 million years in older geologic literature. However, it has been established that these intrusions formed in the period from about 23 to 31 million years ago, usinguranium-lead dating ofzircon andargon-argon dating ofhornblende ;fission track dating also has yielded consistent results (the older, erroneous ages were bypotassium-argon dating ). The intrusions are hosted byPermian toCretaceous sedimentary rocks. The geology of these mountains is similar to the geology of theLa Sal Range and of theAbajo Mountains , both also on the Colorado Plateau in southeastern Utah: locations are shown on a satellite image presented with information about the La Sal Range.American Bison
The Henry Mountains are home to approximately 500
American bison , believed to be one of only four free roaming and genetically pure herds on public lands in North America. The other three herds are inYellowstone National Park ,Wind Cave National Park inSouth Dakota and on Elk Island inAlberta, Canada .The Henry Mountain herd was created in 1941 when 18 bison, including three bulls, were moved from Yellowstone and released near the
Dirty Devil River , south and east ofHanksville, Utah . An additional five bulls were added to the population in 1942. The herd has gradually moved toward the Henry Mountains, frequenting elevations above 10,000 feet. The Henry Mountain herd has beenbrucellosis -free since 1963.A population objective of 325 bison by 2012 has been set by biologists for the Henry Mountain herd. To achieve this objective, and increase overall genetic diversity, breeding animals will be transplanted to other locations. In 2008-2009, Division of Wildlife Resources officials hope to transplant 25 animals to the Tavaputs Plateau in eastern Utah. The new group will be supplemented by up to 20 animals from a herd held privately on the nearby
Uintah and Ouray Indian Reservation . In addition, special licenses are issued annually to hunt the animals and help reduce the excess population. In 2007, eighty-one public once-in-a-lifetime bison hunting permits were available in Utah. (SL Tribune, January 10, 2008, pp. E1 and E2)Management
Much of the area is managed by the United States
Bureau of Land Management .References
* Jules D. Friedman and Curtis Huffman, Jr., coordinators, "Laccolith Complexes of Southeastern Utah: Time of Emplacement and Tectonic Setting -- Workshop Proceedings", United States Geological Survey Bulletin 2158, 1998. http://pubs.usgs.gov/bul/b2158/B2158.pdf
* W. Kenneth Hamblin, Beyond the Visible Landscape: Aerial Panoramas of Utah's Geology. Regal Printing, Ltd., Hong Kong, 300 p., 2004. ISBN 0-9760722-0-3External links
* [http://www.media.utah.edu/UHE/h/HENRYMOUNTAINS.html The Henry Mountains by Roy Webb]
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