Volcanic Plugs
Church rock is one of many remnants of the past volcanism in this area. The feature itself is
a volcanic neck or plug, left after the softer outer layers of the cinder cone have eroded away.
Several of these are found in the area. The largest, Agaltha Peak, can be seen in the
background, to the right of Church Rock.
Some of these plugs have long thin vertical structures extending away from the central
feature, called dikes. These formed as molten lava was pushed up through cracks that
formed in the surrounding rock layers. These layers have since partially eroded away
leaving the dike above the surface.
The most famous of these volcanic plugs and dikes is Shiprock [Tsé bit'a'í].
On the Papago reservation, Baboquiveri, home of I'itoi, is a volcanic plug.
If, like me, you are confused by the terms used to designate geologic time,
a chart, based upon one given in
Roadside Geology of Arizona by H. Chronic is available.
References
- Navajo Sacred Places, Klara Bonsack Kelley, Harris Francis, Indiana Univ Press.
- Native Roads : The Complete Motoring Guide to the Navajo and Hopi Nations,
- Fran Kosik, George Hardeen, Creative Solutions Pub.
- Named in Stone and Sky : An Arizona Anthology, Gregory McNamee (Editor),
- Univ of Arizona Press.
- Talking to the Ground : One Family's Journey on Horseback Across the Sacred Land of the Navajo
- Douglas Preston, Univ of New Mexico Press.
- A Guide Book to Highway 66, Jack D. Rittenhouse, Univ of New Mexico Press.
- Basin and Range, John McPhee, Noonday Press.
- Navajo Country : A Geology and Natural History of the Four Corners Region, Donald Baars, Univ. New Mexico Press.
- The Colorado Plateau : A Geologic History, Donald L. Baars, Univ of New Mexico Press.
- Roadside Geology of Arizona, Halka Chronic, Mountain Press.
© 1994 Karen M. Strom
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