Volume No. 7 Issue No. 7 July 2010  



  Local geology - deposit and erosion
  By Kathleen Wallace

     Matt Morgan of the Colorado Geological Survey has spent the last six months updating the CGS maps for the area north of Falcon.
   It's part of a four-year project to re-evaluate the geology of the Front Range, from Denver to as far south as Falcon, he said.
   Morgan said the soil in the Falcon area is disaggregated bedrock, consisting of feldspar and quartz eroded from batholiths like Pikes Peak and nearby mountains. They were formed from magma that cooled deep in the earth's crust and then were uplifted about 70 million years ago.
   One of the more interesting events occurred more recently - 36.7 million years ago - when a hot cloud of gas and ash erupted from a volcano near Salida, Colo., that has since eroded. The cloud raced over the landscape, filled in the valleys and cooled into slabs of rhyolite, Morgan said.
   The constant movement of water through the area's network of streams and rivers has eroded the slabs, but bits and pieces remain in the form of Wall Mountain tuff.
   Rattlesnake Butte, just north of Peyton, has a bit of Wall Mountain tuff, as does the Castle Rock conglomerate, which forms Castle Rock's cap rock.
   About 10 miles north of Falcon, a ridge known as the Palmer Divide extends eastward from Monument, Colo., toward Limon, Colo.
   Streams north of the Palmer Divide, such as Kiowa Creek, flow northward; and streams south of the divide flow southward, but Morgan expects that to change north of Falcon.
   Someday, Kiowa Creek will erode through the gravel deposits along the divide and join the system of streams that drain southward through the Falcon area, he said.
   It could take awhile.
   Erosion has already removed about 150 feet of rock in the nearly two million years since the gravel was deposited. With 60 feet to go, it might take less than a million years, but it's all a guess, Morgan said.
   It's not uncommon to find petrified wood in this area. Morgan said he's found logs and even whole trees.
   He's also found amazonite, a blue-green feldspar, that most likely came from the Crystal Peak area near Pikes Peak.
   Not all rocks on the surface are from the Front Range. Some are from outer space.
   On Jan. 11, 1998, a meteorite crashed to earth about four miles northeast of Elbert, Colo., but only three pieces were found. Two of the pieces are at the Denver Museum of Nature and Science, and Morgan owns the third. He bought it from Dustin Riffel, the young boy who found it on his family's property a couple of months after the crash.
   Before it broke up, the meteorite was probably the size of a car, but no one was hurt and no buildings were damaged, Morgan said.
   "I hunted that area a couple of years ago but never found any other pieces. With all the tall grass, it's real hard to see," he said.
   According to www.adsabs.harvard.edu, a farmer near the now nonexistent town of Franceville, Colo., in El Paso County, found a meteorite in 1890. In 1974, two meteorites were found near Ellicott.
   Meteorites are often plowed up by farmers or found by ranchers, who incorporate them into walls they're building, Morgan said.
   He might have a chance to look for more pieces of the Elbert meteorite this summer when he finishes up mapping in Elbert County. He expects the entire set of 10 maps will be published by the end of the year.
 
The Elbert meteorite that Dustin Riffel found is small enough to be held in one hand. Photo submitted by Matt Morgan
 
    © 2004-2021 The New Falcon Herald. All rights reserved.