All of My Faults Are Stress Related

I’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 hot rocks closer to the surface, and put them adjacent to systems of fractures. If you’ve got hot rock and fractures close to one another, that should drive the movement of hot water, creating hydrothermal circulation. Above old detachment faults, those remnant hydrothermal systems could have deposited ores. (In fact, given the geology of Nevada and Arizona, I suspect that “could have” is too cautious of a statement.) In modern extensional systems, that means hot springs. (Also not particularly suprising, if you think about your favorite hot spring.) There are several groups looking at old metamorphic core complexes (such as the Snake Range, Nevada), using deuterium and oxygen isotopes to look at the sources of water (from below or above) that interacted with the deforming rocks, and the Colorado Geological Survey is thinking about geothermal systems active todayin the Arkansas River valley (Buena Vista area). (If Durango people want to know more about geothermal energy in Colorado, one of the co-authors of this talk will be speaking at the Four Corners Geological Society on this Friday, Oct. 23. Drop me a note if you’re interested, and I will tell you the details.)

Spatial Skills in the Geosciences: Geologists are good at thinking spatially. At least, that’s what we structural geologists tell anyone who will listen. (Just ask us to point to the nearest beer.) But rather that just brag about it, a group of geoscientists has started collaborating with cognitive scientists to try to understand exactly what’s going on.

- Experience as a geologist actually doesn’t correlate very well with performance on spatial visualization tests. (However, in a talk on Monday, I heard that geologists tended to perform a paper folding test very quickly, though I don’t think they separated novice from expert geologists in that study.)

– One of the most intriguing ideas is software called CogSketch, which is designed to “see” student sketches in the way an instructor would. (Want to give students a quiz to see if they can recognize a fault, and have a computer give the students feedback and then grade the work?) The group that has designed the software is looking for people to help test it, so check their website and contact the authors.

- One of the most worrisome ideas came from studies of eye tracking (seeing where students looked when they read geology textbooks or looked at slides). Carefully examining pictures correlated with understanding the material, but many students only spent a few percent of their time looking at pictures. Didn’t matter how the pictures were integrated with the test – some students only looked at the pictures when they got in the way of reading the words. (And other students, the ones who did the best on post-tests, glanced frequently at the pictures, regardless of how the pictures versus words were arranged.) So much for creative textbook design.

And on top of that, geologists are good at putting distracting things in their photos. Like people, for scale. When students look at a field photo, they look at the person. Or the dog. Or the graffiti on the rock. Forget the GIANT FAULT behind them… the people are more interesting. The authors suggested using a subtle scale instead of people. (But then will students wonder why we keep showing pictures of the change in our wallets, or our rock hammers’ summer vacation?)

- On the other hand, mineralogy classes can dance to learn symmetry. (Simple exercises with hands can also be useful, in my experience, for those who find contra dancing to be an uncomfortably novel experience.) There are videos, with music.

(Warning: I didn’t go to an entire session either in the morning or in the afternoon. I have a bad habit of leaving a room at the mid-session break, getting into a conversation in the hall, and not going back in. This was a typical pattern for the meeting.)

Comments

  1. #1 Karina
    October 29, 2009

    That sounds fascinating. I only took one semester of geology in college but I was fascinated by the wooden models that had been laboriously made with different colors of wood glued together, cut, and glued together again to show different kinds of faults. I think if I’d taken geology sooner in college I could’ve been a geologist.

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