Part of our trip was an exploration of the Geology Road Tour in the middle of the park. The road is an unpaved track that is recommended for four-wheel drive vehicles. We would try to see if that was true on a rainy day!
The process of erosion continues into the present day. Can you see the horizontal scars across the boulders in the pictures above and below? These are areas of intense chemical weathering that formed when the soil levels were about 6-7 feet higher than today. The soils have eroded away within the last 20,000 years or so.
We passed Malapai Hill, a 400 foot high basaltic intrusion. The volcanism resulted from decompression and partial melting of mantle material during a "reorganization" of the crust of southern California as the San Andreas fault system was taking shape. We didn't have time to check it out, but a climb of the hill reveals some nice examples of columnar jointing and fragments of mantle materials in the basalt.
|Malapai Hill, photo by Mrs. Geotripper
A trip spoiled by rain? Absolutely not. There is nothing quite like the sights and smells of a rainstorm in the desert. It was a great day!