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Joshua Tree >
Nature Trail >
Arch Rock
Water At Work
One of the most important factors in considering their evolution has to
do with the natural cracks or joint sets in the rock. You can see these
parallel joint sets as rounded vertical and horizontal breaks where one
rock mass appears to lean against another. While still buried in the Earth,
groundwater percolated into the joints where it slowly decomposed minerals
in the rock along cracks. Some areas with closely spaced joints were
completely reduced to sand, while large rounded rock formations were
left in areas with widely spread joints.
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