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From: Dan Richter (1:317/3)
To: All
Date: Sat, 05.06.21 13:00
ES Picture of the Day 05 2021
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

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

Related EPODs

The Colorado Plateau and a Small Model of Subduction Compression
A Lacy Curtain of Stone Archive - Schunemunk Mountain
Conglomerate Camel Rock, New Mexico Madison Limestone in the
Little Rockies of Montana Granite in Pico das Cabras Park, Brazil

Geology Links

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

Earth Science Picture of the Day is a service of the Universities
Space Research Association.
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