Geology of Red Rock Canyon (Shallow Thoughts)

Akkana's Musings on Open Source, Science, and Nature.

Mon, 23 May 2005

Geology of Red Rock Canyon

I just finished writing up the final project for my field geology class.

The project involved discovering and mapping the geology of Red Rock Canyon. I'll probably upload the paper and other documents later; for now, just a few notes about the field trip, weekend before last.

Red Rock Canyon is in the Mojave desert, near Ridgecrest. I'd been through a few times before, since it's more or less on the way to Death Valley, but of course didn't know any of the geologic details, other than "Ooh, look at the pretty red and white layers and the eroded hoodoos!"

Actually, it's not technically in the Mojave. One of the reasons Red Rock Canyon is interesting is that it sits at the junction of three of California's geomorphic provinces, at the junction of the Garlock fault (dividing the Mojave from the Basin and Range) and the Sierra Front fault (dividing the Sierra from the other two). The Mojave is bounded on its south end by the transverse section of the San Andreas, but Red Rock Canyon is north of the Garlock fault, in the Basin and Range.

Our four day camping trip (two days of hiking, measuring, and mapping, two days devoted mostly to travel) covered a few square miles around the visitor's center, but we ended up with a surprisingly complete map and stratigraphy. Several people had trouble with the temperatures, which were somewhere in the nineties, combined with the pace of the hikes. That's not really all that hot, especially for desert, but it's hot for a group of people coming out of a bay area winter and an unusually rainy spring, especially the students unused to hiking. (This was all rather ironic since we'd switched our mapping project to Red Rock after being concerned about too much snow at the first choice location, June Lake. Those concerns were probably justified; it was snowing up until a few days before we left, so despite the heat, Red Rock was the right choice.)

Nevertheless, Red Rock is a great location to learn geologic mapping. The structure is fairly simple and easy to see (especially from the top of Whistler's Peak), with a series of cuestas of sedimentary layers each capped with basalt, and a couple of other interesting and distinctive layers in between. Luckily for us, there isn't much complex folding, just a fairly continuous tilt caused by uplift due to the El Paso fault (a branch of the Garlock). The rocks themselves are interesting, with lots of olivine and other crystals in one of the basalt layers, and an area at the base of the other basalt layer containing lovely rocks such as opals -- the area used to be an opal mine.

It's also a fairly nice place to camp, with campsites nestled back among towering cliffs (of the Tr5 fluvial member of the Ricardo formation, if you're curious for details) which provides a bit more privacy and separation from other campers than a lot of parks allow. I'm not really much of a camper (I'm a poor sleeper, and I do like my morning shower) but out campsite converted even the timid non-campers in the class.

White-throated swifts play in the turbulence along the face of the cliffs, calling loudly to each other. Their calls woke me up at daybreak each morning, but setting aside sleep deprivation, it wasn't all bad. It's mating season for the swifts, and it turns out they mate in midair. Two birds come together, and locked together they spiral hundreds of feet downward, finally separating just short of the ground. We have white throated swifts here in the bay area, but I'd never seen anything like their aerial mating dance before; let alone seen it set against towering desert cliffs in the stillness of dawn light.

Other interesting natural phenomena observed on the trip: a barn owl flew over the campsite every night, visible against the campfire light. Zebra-tailed lizards were ghostly white except for their black-ringed tails and some ghostly markings on their backs. We saw lots of jackrabbits and several alligator lizards (the latter have been numerous in the bay area as well, this spring). And we saw a lovely horizontal "rainbow" at mid-day of the first day which turned out, after much research, to be a "circumhorizontal arc". I took a telescope along, but we didn't have very good skies (haze, thin clouds, and disturbed seeing, and with all the campfires it was smoky and not even very dark) so we mostly looked at Jupiter, Saturn, and the moon (we did get good seeing at dusk one night for the moon, and we got a good look at the Mare Nectaris shock rings and the beginnings of Rima Ariadaeus).

A few of our group were disturbed to learn on the way down that they wouldn't have cellphone reception at Red Rock. Horrors! They rushed to tie up loose ends, and managed it before we finally lost reception passing by Mojave.

All in all, a very successful trip, although most of us were awfully glad to get home and jump in the shower. I'm even gladder to have my final report finished. Nevertheless, geologic mapping is fun: I'm happy that I had the chance to complete a map of an area like this. I may even be back to Red Rock some day, to try to trace out the extent of that mystery fault at the north end of the pink tuff breccia layer ...

5/25/2005: photos and report are up.

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[ 19:11 May 23, 2005    More science/geology | permalink to this entry ]