 EPOD - a service of USRA

The Earth Science Picture of the Day (EPOD) highlights the diverse processes
and phenomena which shape our planet and our lives. EPOD will collect and
archive photos, imagery, graphics, and artwork with short explanatory
captions and links exemplifying features within the Earth system. The
community is invited to contribute digital imagery, short captions and
relevant links.


 The Colorado Plateau and a Small Model of Subduction Compression

   June 04, 2021


    TomMc_EPOD.CottonwoodCanyonRoadUtah copy (005)

    TomMc_EPOD.DuctileAndBrittleFoldsPhylliteCT.WallRockB (005)

   Photographer:  Thomas McGuire
   Summary Author:  Thomas McGuire

   The cause of the uplift and the compressional features on the
    Colorado Plateau during the  Laramide Orogeny (mountain building
   roughly 60 million years ago) were not understood until it was proposed
   that the  Farallon Tectonic Plate is  subducting at a low angle
   beneath the  North American Plate. This is what raised the whole
    plateau. Additionally,  compressional folding, including dozens
   of asymmetric folds ( Cockscomb, San Rafael Swell, Comb Ridge,
   Raplee Anticline, Waterpocket Fold, and many others) was caused by
   frictional drag with the remains of the subducting Farallon plate. Many
   of the folds are also related to sub-surface compressional
    faulting.

   Small scale rocks often reflect larger regional features. The top image
   is The Cockscomb  monocline along Cottonwood Canyon Road in Arizona.
   The second image is a rock from Connecticut. What is now western New
   England was an area of subduction in the closing of the  Ordovician
   Pre-Atlantic  Iapetus Ocean (about 400 million years ago), which
   created the  Pangea land mass. This rock is a smaller-scale model of
   the Colorado Plateau’s asymmetric compressional folds, like The
   Cockscomb. My drawing on the image shows how this smaller rock
   represents The Cockscomb (a penny is used for scale).


   Cottonwood Canyon Road, Arizona Coordinates: 37.306608, -111.886410


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Geology Links

     *  Earthquakes
     *  Geologic Time
     *  Geomagnetism
     *  General Dictionary of Geology
     *  Mineral and Locality Database
     *  Mohs Scale of Mineral Hardness
     *  This Dynamic Earth
     *  USGS
     *  USGS Ask a Geologist
     *  USGS/NPS Geologic Glossary
     *  USGS Volcano Hazards Program

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   Space Research Association.

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