Vince Cronin: Using GPS, Strain, and Earthquakes in Structural Geology at Baylor University
Provenance: Vince Cronin (Baylor University)
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About this Course
The majority of the students are junior and senior geology majors. I also have some engineering students with strong math but limited geological knowledge.
Three 50-minute lectures; One 2.75-hour lab
Cronin Structural Geology (GEOL3445) syllabus (Acrobat (PDF) 227kB Nov23 16)
The structures of the earth's crust; their classification, origin, and economic aspects; methods of discovery of structures; solution of structural problems; elementary field methods. Two field trips are required.
The purpose of this course is to provide an introductory survey of structural geology for undergraduate students who aspire to develop into practicing geoscientists. This is just an introduction to some fundamental topics, recognizing that structural geology is a very broad field that is fundamental to the geosciences. Students should build a functional understanding of the basic vocabulary and physical processes involved in structural geology. We consider the following topics during the semester: stress, strain, rheology, environmental conditions within Earth (temperature, pressure, differential stress, strain rate, etc.), deformation mechanisms (brittle-cataclastic, low-T plasticity, high-T plasticity), foliation/cleavage development, faulting, folding, and some topics in regional structure.
A Success Story in Using Real GPS Data with Students
I proposed developing this module because I wanted to change from emphasizing finite (deformed trilobites) to infinitesimal strain in my structural geology course. I also wanted to give the students a useful skill involving the ability to use freely available data from the Web. Through coordination by UNAVCO, we partnered with GPS research scientists at the University of Nevada—Reno to ensure that the math and technical components of the strain calculator are correct. Finally a clearer link to societal impacts from earthquakes was added when the materials were brought into the GETSI project.
Students get particularly excited when they learn that GPS deformation analyses are a recent and very much ongoing research area that most geology majors are not even studying yet. They are really tickled to know that they are learning frontier science and not something that has been in textbooks for ages. Learning about earthquakes from the position of research that could be helpful to societal planning empowers them to think about geology in a much more active way. They seem motivated to want to do things to make geohazards more manageable. They were very interested to see the link between GPS measurements of strain in the crust and tangible features like faults and folds that seem to be the product or physical manifestation of the strain that they computed. And where those faults pass through population centers, they came to understand the growing threat faced by the people of those communities.
Students see, understand, and get excited about using real data, the same as geoscientists use, to learn how a wide swatch of the continent deforms and causes earthquake hazards.
My Experience Teaching with GETSI Materials
I pretty much used the materials as they are presented, although not in exactly the same order.
Relationship of GETSI Materials to my Course
I teach a semester-long course in structural geology. I have taught this module in somewhat different versions over the last few years. I usually teach it in the first half or even almost the first thing in the course. I introduce some math concepts before the main module; it is math that I use in the module and throughout the course. Addressing strain in Units 1–4 takes a bit over a week rather than just one week that I used to devote to strain, but I feel that the time is well spent. The Unit 6 final project is in addition to that time, but takes the place of another final project/capstone project that we did on different topics before. I do Unit 5 later in the course to add to my usual teaching about faulting.
- In preparation for this unit, I pass around a signup sheet the class period before and students sign up for one of three options related to doing a little background research on the 2011 Tohoku earthquake in Japan: damage, seismology, or faulting. I tell them to come ready to give a couple facts about these elements and possible preparedness or mitigation that could or did help. I also have them send me a link to the best video they find related to the earthquake. I figure that in looking for a video they like best, they will probably view several and thus it is a sneaky way to get them to learn a bit more about the earthquake.
- Although I sometimes do the physical model exercise as a lab session, I actually am happier with integrating 1–2 physical models at a time over a few different class sessions. This gives the students more practice applying their physical knowledge of strain and deformation to the more abstract or mathematical concepts. I often bring out the stretchy fabric multiple times to help them internalize different kinds of strain as they encounter it.
- I usually introduce the math skills with handouts and worksheets earlier in the course, and let students know that they are foundational skills for structural geology as a whole. It is particularly important for students to learn about vectors. Even the most math-phobic students seem to be able to do okay with basic vector arithmetic. Other math topics are optional depending of the goals of a particular course.
- I pretty much use it as is. Units 3 and 4 tend to blend into each other. I spend about 1.5 days on Unit 3 and then start Unit 4 on the second day.
- I start Unit 3 with the Intro to GPS lecture. Then I have them watch while I walk through getting location and velocity data from the PBO website. I pick a different station (usually something in the Tahoe region because I have research there) and let them see the process before they attempt the Unit 3 exercise and homework.
- The next day we discuss their findings and I give the Oregon-Cascadia presentation to help them visualize the tectonic implications.
- I usually pick up Unit 4 right after the Oregon-Cascadia presentation from Unit 3. I model how they will use the Excel GPS Strain Calculator by plugging in the numbers from the Unit 3 exercise and/or using the example from Tohoku Japan 2011. This prepares them for the Unit 4 exercise. Some of the engineering students are comfortable with MatLab and choose to do the computational part of the analysis with the MatLab scripts that are linked to the module.
- I always have them do this in a jigsaw, in that each student does only one of the three stations. They work together in loose teams for the purposes of discussion and during class; however, each student is responsible for turning in their own write-up for the exercise.
- The class period that the exercise is due, I tell them to bring in some digital copies of what they have found or come ready to write on the white board. Each "team" talks for 5–10 minutes on what they found and I often need to help with ~5 minutes of context or additional clarification (which might involve videos). For example, the engineers will not necessarily have learned about Basin-and-Range extension in previous courses, so I might need to supply some geological context. Thus it takes a 50-minute class period to get through the three case study areas.
- At the end of the class period, I usually say something such as, "Well, it looks like you have had more insights and ideas from this discussion. Would you like one more night to modify and polish your assignment?" They are generally very happy for this opportunity. I pretend it was a last minute decision although I myself know I am planning it. I find the resulting student work (and I think learning) is better for the time to revise.
- Bringing back stretchy cloth can definitely help make the intangible tangible too.
- I found it useful to bring in a couple of pieces of ~1"-thick upholstery foam to use as a physical model of elastic distortion around a fault. On a smooth table, I put the two sheets together along straight edges of the foam. The edge where the two sheets are in contact represents a fault. I have someone hold one of the foam sheets down (away from the fault edge) while another student slowly tries to shear the other foam sheet along the fault between them. Both sheets tend to deform elastically as they stick then eventually slip along the fault. We do this a couple of times so that students can visualize the rotation that occurs on each side prior to slip and the reverse rotation (the elastic rebound) that occurs with the slip.
- I do not think that the students really understand the reoccurrence interval finding, but at least some do come away with the idea that it matters whether you are dealing with a single fault or multiple faults within your GPS triangle.
- I find this really helps to solidify the gains in the earlier units, and I really like it as the "project" for Structural Geology
- I actually do Unit 5 after Unit 6, during a later part of the course related to faults.
- The students seem quite happy to return to looking at GPS data for a somewhat different application.
- For many of my students, this is the first PowerPoint presentation that they have done, so their science communication skills were really stepped up a notch. I was fairly prescriptive about the different slides that they needed to prepare and present. For example, there must be a title slide with their title and name. They must have different data and results slides. There must be slides devoted to societal impacts and mitigation. I urged them to practice out loud ahead of time. The students had about two weeks to pull this project together during their own time. I did allow a little time during intervening classes to check in on their progress and let them ask questions.
Unit 6 is the summative assessment. At first students seemed fairly terrified by Unit 6 as their first experience in "doing research." In the end, however, they seemed to feel that it was a beneficial experience and were glad for the chance. The students were pretty enthusiastic about using their newly developed tool for measuring crustal strain in Unit 5 (after Unit 6 actually), showing that their overall view on the GPS analysis was positive.
The students overall performed fairly well. It has certainly helped to have multiple years to hone and refine the module materials. I feel as if we have pitched the materials at the correct level for undergraduate structural geology students. The module is technically ambitious but achievable. It also serves as a ramp up to possible further work in geodesy in a bachelor's thesis or in graduate school.