Mark Wilson March 12th, 2013
ZZYZX, CALIFORNIA–The spectacular set of folds above are exposed in the lower parking lot of Calico Ghost Town near Barstow, California. This is a famous site that has been visited by hundreds of geologists, but there are still many mysteries about the causes of this deformation and even the correlation of these rocks in the region. The section makes up the Calico Member of the Barstow Formation, which is apparently below the exposed units of the Barstow Formation in Owl Canyon and Rainbow Basin we saw yesterday.
As a true structural geologist, Shelley Judge is here explaining the folding of these beds with her hands and, later, a sketch on notepaper. “Explaining” is not quite the right word: she wrangles information and observations out of the students first before developing the deformation hypotheses. It is not just about a bit of compression!
After exploring a wadi west of the town, we then spent the rest of the morning in Calico. The students above (from the left, Kyle Burden, Steph Bosch, Sarah Frederick, Olivia Brown and Alex Hiatt) are enjoying the main street of this reconstructed 1880s mining community. There are lots of attractions here, from sarsaparilla in the saloon to a classic old-timey mystery shack. One gentleman, hearing that we were geologists, kindly explained to us how Calico Mountain is an extinct volcano with “sandy dikes” full of metals and remnants of lava flows on its sides. It was fun to see our students grapple with the question: do we correct this nonsense or just smile and avoid the hassle? (I just let it pass because I was hungry for lunch!)
In the afternoon we drove south and east along Interstate 40 and Route 66 (yes, the Route 66) to Amboy Crater (shown above). The day had warmed considerably — my thermometer said it was now 94°F. Nevertheless, the stalwart geology crew walked to this gorgeous cinder cone and climbed to its rim from the inside (shown below). I enjoyed learning about the subtle features of the lava flows that emanated from the cone, including pressure ridges and hexagonal cooling joints. This flows and the cinder cone look amazingly fresh. The lava flows have been dated at between 6000 and 500 years old.
The warm temperatures at Amboy brought out some reptiles, to our delight. We saw at least three desert iguanas and many flowers, including the Sand Verbena (Albronia villosa) shown above. It felt like summer, although we were still in the middle of March. Tomorrow is expected to be even warmer. (Yes!)