The original coordinates for this earthcache took you up to a National Forest Service picnic area with an educational sign and a fire lookout. Due to the reception cachers received from the resident lookout, the coordinates have been moved. If you do head up to the lookout anyway (for coordinates see the Aug 2, 2007 log from geoaware), do not mention caching and hide your gps. The picnic area is also open from 8:30A to 4:30p.
The new coordinates take you out a dirt road on Milk Point. You can see the rim to the east through the trees at many locations along the way.
The Mogollon (MUGgy-own) Rim is a 200-mile long escarpment that marks the southern edge of the Colorado Plateau. This escarpment is between 100 and 2000 feet high and is a dominant geomorphological feature of the state of Arizona. The best views are from the fire lookout tower.
There is an informational panel, picnic table, fire lookout tower, and residence at the given coordinates. Visitors are allowed up in the lookout tower from 8 am to 4:30 pm (as I recall). The residence is private and off-limits.
About 80 million years ago the Western US began to be pushed up in a mountain building event that formed the Rocky Mountains. A large area of the 4-corners region (The 4-corners region is where the states Utah, Colorado, Arizona, and New Mexico all meet at their corners), called the Colorado Plateau, was uplifted as one large block.
Relative to the surrounding areas, the geology of the Colorado Plateau is as simple as one might hope for. Much of the area is composed of flat-laying sedimentary layers of rock in order with the oldest rocks on the bottom and the youngest rocks at the top. Periodic volcanic lava flows are found on the top of these sedimentary rocks, sometimes filling the canyons and valleys.
The Mogollon Rim marks the southern edge of the Colorado Plateau. This escarpment was not formed by a fault, but rather by the uniform erosion back from a monocline that formed over a fault. In a monocline, layers bend in one direction between layers of rock, kind of like a ramp. (see the picture to the right source:Dr. Judson L. Ahern ).
The fault created the monocline approximately 15 to 20 million years ago. When the monocline first formed it was approximately 7 miles southeast of this location. Since then, the layers of rock have been eroded fairly uniformly northeastward creating the escarpment.
This escarpment dominates the weather patters of the region. It creates a rain shadow as winds come up from the south, creating the deserts of northeast Arizona and western Utah. It also creates a daily pattern of thunderstorms that are common in the region. Drainage patters off the rim help supply the water needed for the region’s population. Mining and timber industries along the rim helped settle the area.
Send me a note with :
- The text "GCZ5FD Mogollon Rim" on the first line
- The number of people in your group.
- From the informational sign at the original coordinates how many feet of what age rock was eroded to create the escarpment? Since the sign is not at the coordinates, see if you can find this info on the internet. If not the sign is shown on the right. Click it to bring up a larger image.
- For those people who want to do a little resarch, find out the age in years of the geologic age referenced in the first question.
The following sources were used to generate this cache:
- Land, Sky, and People: The Southwest Defined Edited by Joseph Carleton Wilder UNIVERSITY OF ARIZONA PRESS THE SOUTHWEST CENTER TUCSON GEOGRAPHIC FOCAL AREAS OF THE SOUTHWEST http://digital.library.arizona.edu/jsw/3403/geog.html
- Dr. Judson L. Ahern http://geophysics.ou.edu/dynamic/notes/structure/structure.html
- Chronic, Halka, Roadside Geology of Arizona, Mountain Press Publishing, Missolua, Nineteenth Printing, January 2005.