Crust-Busting Faults

George Davis, University of Arizona

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Each student independently researches a major ancient or active regional fault, which she/he has selected from a list provided by the instructor. Each student prepares text and figures that present location, geologic column, map and cross-sectional characteristics, kinematics, mechanics, and plate tectonic significance. Students present results in a poster session to classmates, teaching assistants, instructor, and guests (e.g., other faculty and students).

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Students in undergraduate structural geology

Skills and concepts that students must have mastered

Fundamentals of properties of faulting, folding, and shear-zone deformation; kinematics and mechanics of deformation; plate-tectonic configurations; GPS velocity vector maps and understanding how to 'read' earthquake focal mechanisms.

How the activity is situated in the course

As a 'final exam' assignment/activity, this is a useful integrating capstone experience in structural geology. It serves also as a motivating transition to advanced course work in tectonics, active tectonics, and geophysics.


Content/concepts goals for this activity

Exposure to state-of-the art professionally rendered geologic maps and cross-sections; first-hand experience in searching the literature to identify quality, relevant journal articles; extracting 3D structural geologic insights based on the combination of map and cross-section relationships; discovering the substantive value of integrating multiple data sets. The collective crust-busting faults help build awareness of regional and global tectonics.

Higher order thinking skills goals for this activity

Students learn that regional-scale faults and shear zones comprise the major structures passing through the upper and middle continental crust. Almost all of the main concept-topics in structural geology can be connected to a crust-busting fault framework: geometry, kinematics, and mechanics of formation of faults and shear zones; significance of fault rocks and deformation mechanisms; interplay of folding and faulting; and plate tectonic origin(s). Students come to grasp that each major class of faults has its own distinctive though coherent array of distinguishing properties, reflecting how regional rock formations accommodate deformation in response to tectonic forces and movements.

Other skills goals for this activity

Experience in 're-rendering' published figures in ways to reduce complexity and capture the structural-geologic essence. This includes exercising judgement in relation to the objectives of Crust-Busting Fault Project.  It also offers the moment to begin learning to use and/or apply Illustrator, other drawing technologies, and PowerPoint to create the main elements within a well-designed, effective poster. 

Description and Teaching Materials

Step 1 is to provide to the class an overview of the Crust-Busting Fault Project in terms of step-by-step requirements (see Crust-Busting Instructions) followed by examples of finished poster products (see Crust-Busting Examples, below). These digital products are made available to the students for reference.

Step 2 is to review a list of choices of faults; faults are identified globally (see Crust-Busting Choices, below).  It is vital for the instructor to review the list of choices prior to students making their selections, so that students have a basis to make more informed selections.  Students learn from this overview that the crust-busting fault choices include thrust, reverse, normal, detachment, and strike-slip fault zones and shear zones.  Some crust-busting faults show evidence of long protracted activity accompanied by kinematic shifts.  A natural bi-product of this review is introducing tectonics. 

Step 3 is to have students choose their own crust-busting fault.  Breadth of choice is assured by having a list of choices that well exceeds the number of students enrolled in the class.   It is up to each student to search the literature for journal articles that will inform her/his analysis.  Some students may wish to choose a crust-busting fault that is not on the list.  This is an option but requires that the instructor assure herself/himself that the crust-busting fault desired is one for which there is a solid journal literature of description and interpretation.

Step 4 is to hold the poster session, making clear in advance the basis on which grading/evaluation is carried out (see Crust-Busting Grading). Each student presentation is typically rather brief, less than 10 minutes including Q&A.


Teaching Notes and Tips

It is valuable to emphasize to students the pedagogical distinction between the Crust-Busting Fault Project and Project X. Crust-busting can be a stand-alone activity, but when preceded in the term by Project X there can be certain advantages. Project X eases the way, for it is an analysis of a geologic cross-section, which is a 2D data set. Interpretations are 2D in nature, carried out in the plane of the cross-section.  The Crust-Busting Fault Project is explicitly 3D, where (for a given system) geologic map and cross-sectional relationships taken together are necessary to tell the fuller story.  Project X provides a level of experience and confidence that results in higher potential for performance in the Crust-Busting Fault Project.  Project X is somewhat more prescribed, for when a student selects a given fault/fold system from a list of choices, she/he automatically receives from the instructor a PDF of a journal article that contains the geologic cross section. When students select their own crust-busting fault from the list, they themselves have the responsibility to track down good references. 

Each project requires that the main elements (geologic cross-section, map, and column) on the poster are NOT just 'cut-and-paste' products, but instead have been transformed by the students through use of Illustrator or simply tracing and adapting primary source materials in ways that stratigraphic units are grouped; faults are effectively named, labeled, and emboldened; and a common color-coding is established.  Likewise, the interpretive figures and drawings, including plate-tectonic maps, are adapted and not just 'cut- and pasted'.  It is the act of adapting and transforming that stimulates deeper learning and understanding.

It is critical that instructors make students aware of the integrity line separating appropriate paraphrasing, quoting, and referencing from journal articles, versus plagiarism.  The specialized language of journals is challenging to most undergraduate students, and there is a temptation for some to paraphrase journal-article language much too closely. Instructors can remove students from harm's way by insisting that their posters NOT contain paragraphs and sentences of responses, but rather bullet points containing and expressing the critical information and observations. Emphasize the requirement of 'putting things in your own words.'


The Crust-Busting Fault Project is a graded exercise, counting ~15% of the final grade in the course. Most points are awarded for the quality and effectiveness of the poster and the poster elements, though the effectiveness of the student in presenting her/his poster is also rewarded.  In the assessment individual oral presentations, 'grasp of the material' is perhaps the most important consideration. 

The Crust-Busting Fault Project and Project X are research engagement activities that are as far removed from a 'standard hour exam' as can be imagined.  Herein lies part of the value, for it provides instructors with the means to see and assess a different array of competencies in their students. Some students who struggle on exams thrive in this type of independent research; and the reverse also can be true.  Based on more than a decade of capping-off undergraduate structural geology with the Crust-Busting Fault Project one thing is clear: There will be strikingly positive feedback from many students who underscore their satisfaction in 'owning' their own fault. They contrast this with their experience with the most common university assignments and tests, which are completely externally driven towards them by others (teacher, teaching assistant). These projects are, to a degree, clean slates and offer some freedom of direction and design, ironically in spite of the fact that the requirements are actually rather tightly constrained so that students do not unnecessarily 'spin their wheels.'

References and Resources

Examples of student products are the most valuable and practical of all resources in conveying to students what is expected.Here are two examples, shared with the authors' full permission:

  • Anna Miller's Crust-Busting Fault Project (2020) on the Alpine Fault: Miller, Alpine Fault.pdf (Acrobat (PDF) 11.7MB Oct14 20)
  • Kerst Kingsbury's Crust Busting Fault Project (2020) on the Polochic/Montagua fault in Guatemala: Kingsbury, Guatemala.pdf (Acrobat (PDF) 7.6MB Oct14 20)