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| North America is moving westward over the Pacific Plate at one or two
inches per year. When tension builds in rocks from this collision, the strain
is released along faults in the form of earthquakes, as the rocks finally
break. |
| Joshua Tree is crisscrossed with hundreds of faults, and is a great place
to see raw rocks and the effects of earthquakes. The famous San Andreas
Fault bounds the south side of the park, and can be observed from Keys View.
Blue Cut Fault in the center of the park can be seen from the hilltop behind
Lost Horse Mine. The fault forms the straight, abrupt base of the Hexie
Mountains east of Queen Valley. |
| Fault zones are important factors in localizing natural springs. Movement
by faults causes impervious zones of shattered rock fragments to form an
underground dam forcing ground water to rise. The Oasis of Mara at the visitor
center in Twentynine Palms marks the Pinto Mountain fault. The park has
four other fault-caused oases that support the native palm tree, Washingtonia
filifera. These oases supply food and water to a wide variety of wildlife
and point to the connection between the park’s geology and its wildlife
habitat. |
| Will Joshua Tree National Park experience a large earthquake anytime soon?
Despite a great amount of recent seismic research, no one can yet predict
earthquakes with any accuracy. The earth will continue to shake in Southern
California, and most earthquakes will be small— “felt” by
seismographs, rarely by people. Occasionally, a larger one will occur, but
when or where remains unknown. |
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http://www.nps.gov/jotr/nature/features/geology/faults/faults.html
last modified: 03/27/02
web editor: Sandra kaye |
