Faulting and Folding

A simple glance at the Grand Canyon is enough to know that forces have acted upon the rock formation to transform the canyon into the shape we see today. Two of these contributing forces are faulting and folding, and both occur as the earth’s crust is strained. Faulting occurs when the stress on a landscape is so great the landscape responds by breaking, creating a fracture on the surface. As opposed to earthquakes which are experienced as faults occur, the fault itself is the physical evidence left behind. Faults are caused by stress in the form of compression, extension, and side-by-side movement. Compression creates thrust faults, extension creates normal faults, and side by side motion creates strike-slip faults.

http://media.tiscali.co.uk/images/feeds/hutchinson/ency/c00948.jpg
 

According to the National Park Service, faults can be seen in most of the canyon’s rock layers. The movement measures from 15 to 16000 feet. One of the most famous faults at the Grand Canyon is Bright Angel Fault. Bright Angel Fault began as a normal fault 1700 million years ago, but has been reactivated twice since that time as a thrust fault, then again as a normal fault.  




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http://www.wvgs.wvnet.edu/www/geoeduc/SedimentaryRocks/CSR09.jpg

Folding occurs when the stress on the landscape is not enough to cause it to snap, but enough to deform it or bend the landscape. Synclines are distinguished by their downward fold, anticlines through their dome like upfolds, and monoclines by a single slight bend.

 

At the Grand Canyon, most of the folds are monoclines. One of the most distinguishable folds is known as the East Kaibab monocline. I remember looking out of the observatory station of the Desert Watchtower, but little did I know I had the best view of the East Kaibab monocline. I plan on visiting the Grand Canyon again, and next time I will know whether I’m staring at a fault or fold.

 

 

 

 

Sources

http://www.physci.mc.maricopa.edu/Geology/FieldTrips/GrandCanyon/GrandCanyon_2004_Fall/GrandCanyon_2004_Fall_Images_640/DSC04383.JPG

http://www.nps.gov/grca/naturescience/upload/2-Grand-Canyon-Geology6-2009.pdf

http://www.physicalgeography.net/fundamentals/10l.html

http://www.nps.gov/grca/naturescience/faults.htm