More than one billion years of time is represented by the contact between Tertiary rocks and Precambrian rocks on Camelback Mountain, in Phoenix, Arizona.

   This contact between two rock formations on Camelback Mountain represents over 1 billion years of "missing time"! In geology, such a contact between rocks is called an unconformity.
   Notice the dividing line running from near the center of this photo to the lower left corner. Rock ( / , above that line is the age (approximately 30 million years old) Camel's Head Formation. Below that line is (~1.7 billion year old) , which forms the slope below the vertical Tertiary rock face.
   This feature can be seen in many places on Camelback Mountain -- this picture was taken just off of the Echo Canyon Trail to the summit. In the background of this northeast-looking view are the McDowell Mountains.
   You can read more about these rocks in my FREE, short GeoStory™, called "Missing Time" (< 1 MB, download as a PDF).

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   See the GeoHistory page if you want to know more about why the landscape looks the way it does, or return to the map of "The Rocks of the Valley of the Sun" for more view locations.
   You can also send this as an E-Postcard to your friends!