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 Information Entries for Mt. Wilson

Geology (Mt. Wilson)



Title: Mt Wilson Geology

Entered by: ztop

Added: 10/12/2010, Last Updated: 10/12/2010

Sources: Blair, Rob; 1996, Origin of the Landscapes of the San Juan Mountains; in The Western San Juan Mountains: Their Geology, Ecology and Human History; University of Colorado Press, Boulder, Colorado. Faure, Gunter, 2001, Origin of Igneous Rocks:the Isotopic Evidence; Springer-Verlag, Berlin. Fielder, John, 2004 , Mountain Ranges of Colorado; Westcliffe Publishers, Boulder, Colorado Lipman, Peter; Thomas A Steven, and Harald H Mehnert, 1970, Volcanic History of the San Juan Mountains, Colorado, as Indicated by Potassium–Argon Dating; GSA Bulletin; August 1970; v. 81; no. 8; p. 2329-2352;

Mt Wilson, Wilson Peak and El Diente contain some of the youngest rocks of any 14ers in Colorado. The rocks forming them are related to the volcanism in the San Juan Mountains during the Tertiary Period.
During the Pennsylvanian (~250 million years ago) the area wasuplifted as part of the Uncompahgre highland, which covered much of western Colorado. Both the Uncompahgre and Front Range uplifts were a product of plate tectonic activity to the southeast as Africa collided with North America. At the end of this tectonic activity, the mountains were worn down and gradually the sea crept over the area. Marine and then fluvial sediments were deposited during Jurassic and Cretaceous time as the seaway that covered the area was filled in. These sediments covered the entire San Juan Mountain area at the start of volcanic activity.
Volcanic flows in the San Juan Mountains began during the Oligocene Epoch, 30-35 million years ago. The earliest volcanic flows were made up of lavas that flowed easily across the landscape punctuated by occasional explosions of ash and rock. These rocks covered much of the southern Rocky Mountains, although a lot of it has since been eroded. As the eruptions continued, magma apparently moved closer to the surface, finally collapsing the volcanoes above and creating huge craters called calderas. The broken rock of the calderas were places where hot, mineral-rich solutions could move through the rocks and deposit the gold, silver, lead, copper and zinc ores which were mined in Silverton, Creede, Ouray, and Telluride.
The Wilson Group is made up of the roots of these volcanoes. Called stocks, they are small intrusive igneous rock bodies. Intrusive igneous rocks are magma that never made it to the surface, but cooled and hardened underground. As the mountains were eroded, these hard intrusive igneous rocks became the high points in the range. They are relatively fine-grained and fracture easily, making the rock loose and creating the nasty scree slopes on the flanks of the mountains.
During the Pleistocene these mountains were extensively glaciated creating the sharp ridges, steep walls and deep cirques that are so distinctive of the San Juans. Permanent snow fields on the flanks of Mt Wilson are the remnants of some of these glaciers. An interesting glacial feature that may still be active in the San Juans are the rock glaciers which can be seen in Silver Pick Basin and on the flanks of Mt Wilson. Ice under the rock glaciers allows downhill movement of the rock pile as it deforms under the weight of the rock.


Name History (Mt. Wilson)



Title: Naming of Mt. Wilson

Entered by: 14erFred

Added: 05/14/2010, Last Updated: 05/14/2010

Sources: Foster, M., Editor. (1984). Summits to reach: Report on the topography of the San Juan Country by Franklin Rhoda. Boulder, CO: Pruett Publishing Company. Hart, J.L.J. (1977). Fourteen thousand feet: A history of the naming and early ascents of the high Colorado peaks (Second Edition). Denver, CO: The Colorado Mountain Club.

The mountain was named not for President Woodrow Wilson, as some have suggested, but for A.D. Wilson, chief topographer of the U.S. Government's Hayden Survey of 1873-75 (for whom nearby Wilson Peak was also named). Wilson was one of the foremost geographers and mountaineers of the 19th century. He not only helped to chart the topography of Colorado's highest mountains, but also made the first ascent of five Colorado 14ers (Uncompahgre, Sneffels, Sunshine, and Mt. Wilson, in 1874; and Handies in 1875) and the second ascent of two others (Rainier in 1870, and Blanca in 1875).

Allen David Wilson was born in Sparta, Illinois, on September 17, 1844, but traveled with his family to the Pacific Northwest via the Oregon Trail in the spring of 1850. He left college in 1867 before graduating, in order to become an assistant topographer with the Geological Survey of California. There he learned the art of surveying by triangulation and mastered special techniques for extending continuous triangles across alpine country. From 1868 to 1872, he worked as assistant topographer for the US Geological Exploration of the Fortieth Parallel, spending the winters in Washington helping to prepare maps and publications.

In the fall of 1872, he collaborated with several other members of this survey team to expose the infamous Great Diamond Swindle. Two prospectors arrived in San Francisco claiming to have found diamond mines worth millions of dollars. They led an eager group of potential investors to a prearranged site that had been "salted" with gemstones that the swindlers had previously purchased abroad for about $30,000. After finding diamonds in soil samples, several very respectable financiers formed an investment syndicate that bought out the promoters for $600,000. By some shrewd detective work, Wilson and his colleagues determined that the alleged mines had to be in territory examined that very summer by the Fortieth Parallel Survey. Finding it hard to believe that such riches had been found under the noses of expert geologists by a couple of lucky prospectors, Wilson and the others secretly returned to the field and found a site staked out, complete with a sprinkling of diamonds, in the NW corner of Colorado. They spent the next two days systematically studying the soil, before concluding that a terrible fraud had been perpetrated. They returned immediately by train to San Francisco with their evidence, exposed the unpleasant details, and saved further loss by new investors.

On July 10, 1879, Wilson was appointed chief topographer for the US Geological Survey. He served in this position for two years, preparing maps of the area around Leadville, Colorado, and of the nearby Mosquito Range. Because of Wilson's wide-ranging experience in Colorado and his outstanding reputation, no one was surprised when in 1885 the General Land Office called on him to settle a dispute about Colorado's western border, the 109th meridian. During the official survey of 1878, the topographer, Rollin Reeves, had been unable for 11 nights to take observations on the North Star to keep him on a true north course (due to bad weather). As a result, he strayed 11 degrees too far west for nearly 8 miles; and this survey error had given Colorado a 100-mile chunk of Utah. Wilson's resurvey of part of the 109th meridian confirmed the mistake, but since Reeves' survey was official, the border remained and is today still unchanged.

Deliberate and careful in all aspects of his career, Wilson was likewise prudent in his private life. He did not marry until 1895, at the age of 50. His wife was Amelia Stevens, daughter of a prominent California pioneer who had built a substantial shipping business. Wilson died of influenza on February 21, 1920, at the age of 75.


Name History (San Juan Mountains)



Title: Eolus

Entered by: wojtekrychlik

Added: 01/21/2014, Last Updated: 01/21/2014


Aeolus was the ruler of the winds, according to Greek mythology.
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