Structural Geology and Tectonics

Barbara J. Tewksbury, Department of Geosciences
Hamilton College

Summary

Rather than taking students through the topics of structural geology in textbook table-of-contents order, this course is framed around having students apply concepts and methods of structural geology and tectonics to answer the overarching question, "What is the earthquake risk in the Seattle/Puget Lowlands area of Cascadia, and why?" Students build experience with the key concepts, analytical methods, and relevance of structural geology and tectonics using real-world data sets as, over the course of the semester, they investigate the many structural and tectonic questions that must be answered to evaluate the risk.


Course URL: []
Course Size:
15-30

Course Format:
Lecture and lab

Institution Type:
Private four-year institution, primarily undergraduate

Course Context:

This course is a required core course for a major in Geoscience at Hamilton, and the only pre-requisite for the course is one introductory course in geoscience. This is true of our other core courses as well (min, hydro, seds, and paleo). Furthermore, there is no prescribed sequence for taking the core courses, so students in Structural Geology and Tectonics range from first year students to seniors, with backgrounds ranging from only one intro course to a full set of required courses for majors. Because introductory geology courses at Hamilton are topical, students in Structural Geology and Tectonics also bring very different backgrounds from their intro courses. Not only is this varied course preparation an asset in terms of student/student interactions, but my experience indicates that students with less preparation are not at a disadvantage. In fact, some of the highest grades in the course have been earned by first year students.

Course Content:

The topics incorporated in this course are typical of a standard structure/tectonics course (fold and fault systems/strain significance/kinematics, rock rheology/deformation mechanisms/fabrics, stress/strain, maps/cross sections, plate boundary features/processes, strain rate/strain style, etc.). Students encounter topics and concepts in an order that is relevant for answering specific questions related to assessing earthquake risk in the Puget Lowlands/Seattle area. For each question, students learn the underlying concepts using examples from around the world and then apply what they have learned to evaluate a particular aspect of earthquake risk in the Puget Lowlands/Seattle area. For example, students combine what they have learned about fold/fault systems with data from focal mechanisms, GPS installations, geophysics, and modeling to analyze the geometry, kinematics and earthquake potential of shallow crustal faults in the Seattle Uplift. As another example, students apply what they have learned about rock rheology, deformation mechanisms, and pore fluid pressures to evaluate how and why these properties and processes change along the subduction interface and how that affects earthquake risk.

Course Goals:

  • Students will be able to describe and interpret geologic structures in unfamiliar geologic maps and aerial/satellite images, to construct cross sections, to infer geologic history from map and image data, and to interpret structures in the context of regional tectonic history.
  • Students will be able to make appropriate observations of structures at different scales, ask relevant questions, collect and/or evaluate appropriate data, and make evidence-based interpretations about the processes and histories by which the rocks reached their present form.
  • Students will be able to combine the tools and concepts of structural geology with other geologic and geodetic data sets to evaluate the context, setting, cause, and risk of damaging earthquakes and associated hazards in a particular area and make related informed decisions.

Course Features:

Although this course meets for a typical total of 6 hours per week, the course is not structured around the typical three 1-hour lectures plus a 3-hour lab. Rather, this course meets for 2 hours three times a week. During each 2-hour session, students are actively engaged in short lab activities, individual and group work (e.g., brainstorming, jigsaws, gallery walk, concept sketches) and discussion interspersed with mini-lectures. This gives students an opportunity to immediately apply what they are learning, and it gives me an opportunity to immediately address aspects where students are struggling. Students must also complete a homework assignment before each class session to consolidate what they have learned and to prepare for class. Both the class structure and the daily homework are critical components of the learning environment in this course.

Course Philosophy:

Several years ago, the Geo Department at Hamilton made a decision to thread a Cascadia theme throughout all of the core courses for majors. Each of these courses incorporates aspects of geologic processes in Cascadia, and students use what they have learned to build their understanding of Cascadia over multiple courses. We chose Cascadia because geologic processes and societal issues are particularly strongly linked, the questions and approaches span the fields of the geosciences, and we can provide students with firsthand experience in the need for collaboration across disciplines to address complex geological problems of societal significance. Approaches range from incorporating specific modules to teaching fundamental principles throughout a course using Cascadia examples.

Only a very small percentage of students in my structural geology course will go on to become professional structural geologists. Framing the entire course around earthquake risk in the Puget Lowlands/Seattle area allows me to teach concepts of structural geology and tectonics that are relevant to who my students are and how they might use these concepts in their personal futures as geologists in other subdisciplines. The Puget Lowlands/Seattle analysis also provides students with a template framework for the kind of data gathering and analysis that they should do in their personal futures whenever they move to a new place.

Assessment:

I use the daily homework to assess student progress on individual skills and tasks. Rather than giving hour exams or a midterm, every third homework assignment includes "micro-exam" questions that students must do on their own and that provide new scenarios for students to evaluate (i.e., ones that we haven't covered in class but that require them to apply what they have learned). We also have a culminating field trip in the course so that students can apply what they have learned (once the snow has melted off the outcrops at the end of April....). The final assignment for the course requires each student to synthesize the various pieces of earthquake risk analysis that they have done over the semester plus write an essay on how they would approach an earthquake risk analysis for a new area that they might move to in the future.

Syllabus:

Tewksbury Structure syllabus (Microsoft Word 2007 (.docx) 1.2MB Aug23 19)

References and Notes:

Earth Structure (online version) by van der Pluijm and Marshak
Various readings from the literature. Please contact me if you would like a list or would like to have copies of specific assignments/activities.

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