Armed Intrusions
April 23, 2006
Referred by: Dave Moser
Summary authors & editors: Dave Moser; Jim Foster
The photo above showing what looks like a huge fossilized spider or a giant octopus was photographed on Februaty 11, 2006 at Soldier Canyon, near Tucson, Arizona. This curious rock formation is likely partially composed of gneiss (metamorphic rock). The "arms" that protrude from the rock surfaces are actually dikes -- intrusions of harder rock eroding at a slower pace than the host rock formation.
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