structural geology
khannula | November 1, 2009Go to Dave's Landslide Blog for full details about this. I don't have access to the paper.
According to Dave Petley, there's a new paper in Nature Geoscience about the Slumgullion landslide. Slumgullion is in my greater neighborhood - it's in Colorado's San Juan Mountains, between Lake City (former home of Alferd Packer) and Creede (former home of Doc Holliday), and I think it's got the coolest name of any landslide (and possibly the coolest name of any geological feature). It's a strange landslide for its slow movement, and it's being monitored in excruciating detail by the US Geological…
khannula | October 20, 2009I'm heading home tomorrow, and I've finally got a little time to blog. Here's quick summary of the sessions I went to on Sunday (the first day of the meeting).
Detachment Dynamics: heat, deformation, and fluids in extensional systems: Where continental crust stretches apart, steep normal faults join at depth into detachment systems: shear zones that separate hot, ductilely deforming rocks from shallower, brittly deforming rocks. These systems have been discussed since the 1980s, but the focus in this session was a little different than in past discussions I've witnessed. Detachments bring…
khannula | September 2, 2009I've spent 15 hours in the classroom teaching in the past three days, and several more meeting with students to sort out schedules and brainstorm ideas for senior thesis projects. My brain is fried, but I'm going to try to share some interesting stuff I've run into:
- Early this afternoon, I posted a frantic plea for good Google Earth locations to use to demonstrate tilted rock layers in my first Structural Geology lab. I should have just checked SERC first. They now have a collection of images and latitude/longitude coordinates that are both beautiful and beautifully deformed. I started my…
khannula | July 28, 2009Last month, another structural geologist came to town to check out possible sites for a future field class. While we were out looking at one of my favorite teaching sites, he commented that geologists seem unusually willing to share their secrets with one another. (We had met at one of the Cutting Edge workshops, where great teaching ideas are free for the taking, technically unpublished but shared online and in person.)
A few weeks ago, I learned about another example: Outcropedia, a project of the International Union of Geosciences' TekTask group. From the organizers' e-mail:
The…
khannula | July 6, 2009One of the tricky things to convey about rocks, especially in a lecture or in a textbook, is the way geologists can see such different things at different scales - from thousands of kilometers to a few micrometers - and the way that all those observations fit together to understanding the processes that shape the Earth. Static photos, whether on paper or projected onto a screen or on a computer, don't convey all the information that one can get from a single outcrop - standing back from it, climbing up close to it, crawling over it with a hand lens. (And that's leaving out the perspective of…
khannula | May 30, 2009I made a promise to myself that every month, I would at least look through the abstracts on my RSS feeds and note interesting articles that I wanted to find time to read. So now it's May 30, and I'd better do it before the June issues come out.
So... articles in the May issue of Geology that look interesting:
Extensional tectonics: Extension rates, crustal melting, and core complex dynamics. Metamorphic core complexes are made up of metamorphic and igneous rocks that have been brought nearer to the surface by continental extension. They're characterized by mylonites that separate the hotter,…
khannula | May 6, 2009I'm neck-deep in a five-week summer class, and spending my evenings reading for class prep and thinking about how to run discussions. So I'm on a blogging semi-hiatus, at least until I've got an hour or two free of other commitments. In the meantime, I'll occasionally post some of my old favorites. This one was my first blog post ever, and was included in the 2007 Open Lab.
NPR has had this series, off and on, in which listeners record interesting sounds and then explain them on the air. I didn't have a recording device with me last weekend, but I literally stumbled across some of the most…
khannula | April 15, 2009The cores of mountain belts formed by continental collisions often contain metamorphic rocks, formed when sediments were buried in the collision and transformed by heat and pressure.
But the heat and pressure don't happen simultaneously - rocks can be buried (and increase in pressure) much faster than they can heat up. When the rocks are not allowed to heat up significantly, this process can create blueschists, the high pressure/low temperature metamorphic rocks formed in subduction zones. In continental collisions, subduction stops, and the metamorphic rocks sit around at depth, heating up…
khannula | April 13, 2009My reviewers commenters on yesterday's post on chocolate chip cookie deformation had some great points. (Some of them also seem to have been very hungry. For those who want me to experiment more, and to get to analyze the results: looks like I've got something that I can promise once the Donors Choose challenge rolls around.)
Key criticism #1, from DDeden:
First the cookies puffed up, and then they collapsed. While they puffed up, their surface area increased [No, it decreased!], so the cookie crust was pulled apart. When the cookies collapsed, the surface area decreased again [No, it…
khannula | April 12, 2009I probably shouldn't have baked chocolate chip cookies yesterday, what with today being one of the two biggest chocolate-buzz holidays on the American calendar. But I did.
I've had a lot of trouble figuring out the best recipe adjustments for high elevation. My cookies have a tendency to puff up big, and then collapse into goo. The end results look like this:
All wrinkled around the edges, and flat in the middle. In fact, it looks like something I could map:
Those are fold symbols for the wrinkles around the edge, and normal fault symbols for the places where the crust broke open to reveal…
khannula | April 6, 2009The estimated death toll from last night's M 6.3 earthquake in Italy is currently 150, with 10's of thousands of people left homeless. My thoughts are with the people there, especially those still searching for their loved ones.
As you can see from the USGS map and moment tensor (and from Highly Allochthonous, who posted a great explanation while I was on kid duty), the earthquake occurred on a normal fault associated with the collision of Africa and Europe...
At this point, if you've taken an intro geology class, you're probably shaking your head, wondering if I've made a mistake reading…