18 January 2008
So I am obviously unable to handle the “Friday Field Foto” thing, but I thought it would be fun to do a series of posts on field trips I’ve taken. We’re off to Texas this week, with some photos from a field course I TA’d in and around Big Bend National Park last May. This is by no means going to be a comprehensive description of the geology, but more like a few highlights of the trip.
Naturally, I’m going to start with my favorite volcanic feature. Willow Mountain, on the east side of State Highway 118 three miles north-northeast of Study Butte in southwestern Brewster County and on the way to Terlingua Ghost Town, is a rhyolitic laccolith formed about 40 million years ago in the “aftermath” of the Laramide Orogeny.
We didn’t get a chance to see it up close (which I really wanted to do, but I was afraid someone was going to come out with shotguns and run us off if we trespassed on their land, not to mention we were running late to get back and cook dinner). The best part about Willow Mountain is the spectacular columnar jointing, which you can see better here:
This is actually not a very well-known example of columnar jointing in the US, from what I can tell; other places (like Devils Postpile in California, Devils Tower in Wyoming, and Sheepeaters Cliffs in Yellowstone) seem to get more recognition. I highly recommend visiting this one, though, if only because it’s in an area that’s absolutely teeming with volcanic features.