Thursday, February 21, 2013

Cheating Death One More Time: Home from the Field

Sunset in Death Valley near Badwater
Hey, I'm back, after five days in the wilds with no wi-fi access, and no television. Did anything happen while I was gone? What about that asteroid that was making a close pass...did it cause any problems? I sure wouldn't want to be around if a big chunk of space rock actually entered the atmosphere...

Okay, I actually did hear about the Russian near miss, and because our media access was really limited, we first thought we were hearing that 400 people had DIED. It just goes to show how stories can get out of hand. What an extraordinary event however, and what a relief that no one actually was killed.

Meanwhile, I've had a delightful weekend doing what I love: teaching geology in the field, this time mostly in Death Valley National Park. There is such a difference between drawing lines on a chalkboard to represent rock layers, and standing in front of the real thing.
Our group included a fair number of geology majors, but most were new to the science, with only a few weeks of a lecture class completed before we tossed them, kicking and screaming, onto an outcrop of rock (actually, this was a stand-alone class, and all the students had chosen to be there).
To get our new students up to speed, we started in the Renaissance, reviewing the basic rules of stratigraphy as described by Nicolas Steno in the 1600s: superposition, original horizontality, and lateral continuity (I described these principles in detail last year, in this post). These principles allow us to start discerning the sequential story of these rocks. We did some basic rock identification so the students could start determining the ancient environments that were responsible for these sediments. Note the preponderance of reds and browns; these rocks were exposed to oxygen at the time of their formation and burial. The region was also subject to occasional volcanic activity, as shown by the white ash layers (which also provide a means of accurately dating the rock).

The sedimentary sequences were cut by a series of minor faults, providing us with an introduction to tectonic processes, as well as offering a fine example of cross-cutting relationships. Ultimately, the students were able to work out a reasonably complete sequence of events that produced the spectacular red cliffs.
Although we couldn't see any at this locality, we talked about the rich fossil record at this site, a group of animals that included early species of horses and camels, large predatory ancestors to wolves and bears, and large grazing species similar to rhinos.
All in all, Red Rock Canyon State Park in the Mojave Desert of California is a great place to introduce basic principles of geology. When we finished up here, we were ready to take on the much more complex landscape of Death Valley National Park.

1 comment:

Unknown said...

Best pics of Red Rock Canyon I've seen. Alas, I've never really been there; it was always a potty stop on class field trips on our way to Owens Valley.