In the last post, we were introduced to the basic rules of stratigraphy as they stood exposed in the spectacular cliff faces of Red Rock Canyon State Park in California's Mojave Desert. A classroom chalk board can only provide a cartoon of these concepts, so there is nothing quite like being there and laying your hands on these records of the Earth's past. We were on the road with 30 community college students, most of whom were seeing this landscape for the first time. After an introduction to the stratigraphic principles of superposition, original horizontality, lateral continuity, and cross-cutting relationships, I sent the students forth to test their newly acquired knowledge against the cliffs above. We weren't quite to the point where we could do geologic mapping, but I provided them with an outlined photo of the scene (below) and asked them to describe the rocks, and identify any structures.
extinct elephants, rhinos, three-toed horses, giraffe-like camels, saber-toothed cats, and bone-crushing dogs as well as smaller animals like ancestral skunks, martens, alligator lizards, rodents, and shrews. (follow the links to descriptions of each type of animal on the Los Angeles Natural History Museum website).
Faults in a cartoon drawing on a chalkboard are a lot easier to see than most faults in the real world. A number of the students noticed how the layers ended and identified the fault that caused them to be offset (see the arrows in the diagram above). I headed up to take a closer look at the fault surface...because I think everyone should know their faults...
If postings seem sparse in the coming week, it would be because we are about to embark on part two of our Strangers in a Strange Land journey: an exploration of the Mojave Scenic Preserve in the desert south of Death Valley. We're attending the spring meeting of the Far Western Section of the National Association of Geoscience Teachers at the Desert Research Center at Zzyzx. Hope to see a few of you there!