Intrusions, Mojave Desert, California

Steven Dutch, Professor Emeritus, Natural and Applied Sciences, University of Wisconsin - Green Bay

Location: Viewpoint at 34o 50' 02" N, 115o 00' 42" W (Google Street Scene duplicates this vantage point). Mountain peak at 34o 50' 43" N, 115o 01' 34" W.

The dark colored rocks on the mountain peak are Paleozoic sedimentary rocks, colored dark brown by desert varnish. The light rocks low on the mountain are granite, the top of a large intrusion. Several light streaks running up from the granite are dikes, sheetlike intrusions of magma intruded along cracks in the crust.

The dark ridge in front of the mountain is a hogback, a ridge defined by a sloping bed of resistant sedimentary rock. The rock layer is dipping toward the mountains and the rocks on the top of the ridge are the edge of the resistant layer.

The low embankment in the foreground was constructed to keep flash floods from washing debris onto Interstate 40.

Original Scene

(author's image)

Possible Coloring

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Created 19 July 2009, Last Update 15 January 2020