Joshua Tree National Park
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I hadn't expected the fantastic rock piles when visiting the Joshua Tree National Park. They are a spectacular sight, as are the beautiful Joshua trees. We were able to spend a couple of days here as we stayed overnight in Twentynine Palms, a nearby city. We walked through the amazing desert and you could really tell where the Mojave desert changed to the Colorado desert due to the difference in landscape. The best moments of our visit for me was breakfast in the park and the family of coyotes we saw.
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The park is where the Mojave Desert (high desert) meets the Colorado Desert (low desert). It is famous of course for its abundance of Joshua trees. The park encompasses some of the most interesting geologic displays in all California deserts. Exposed granite monoliths and rugged, twisted rock mountains testify to powerful earth forces. Washes, playas, alluvial fans, bajadas, pediments, desert varnish, plutons and active faults create complex landscapes of immense beauty.
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The rockpiles here are an amazing sight and geologists believe the landscape was born more than 100 million years ago. Molten liquid, heated by the continuous movement of the earths crust, oozed upward and cooled while still below the surface. These plutonic intrusions are a granitic rock called monzogranite. The monzogranite developed a system of rectangular joints. One set, oriented roughly horizontally, resulted from the erosion of the miles of overlying rock. Another set is oriented vertically, roughly paralleling the contact of the monzogranite with its surrounding rocks. The third set is also vertical, but cuts the second set at high angles. The resulting system of joints tended to develop rectangular blocks. As ground water percolated down through the monzogranite’s joint fractures, it began to transform some hard mineral grains along its path into soft clay, while it loosened and freed grains resistant to solution. Rectangular stones slowly weathered to spears of hard rock surrounded by soft clay. After the arrival of the arid climate, flash floods began washing away the protective ground surface. As they were exposed, the huge eroded boulders settled one on top of another, creating the impressive rock piles.
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Below are a selection of photographs from my visit there.
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