Tectonic Geomorphology: Exploring activity on the San Andreas fault with ArcGIS
Summary
In this activity students develop an hypothesis as how slope morphology reflects the timing of motion on a fault, in this case the classic Wallace Creek segment of the San Andreas. It is a scaffolded, problem-based exercise that uses ArcGIS and LiDAR data to test their hypothesis.
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Context
Audience
This assignment was developed for a sophomore level geomorphology course with enrollments on the order of 20 students. This course also serves as the key GIS course in our department's major. It serves geology majors, environmental science majors, and non-majors seeking a second core area science lab course.
Skills and concepts that students must have mastered
Students will have completed the ArcGIS tutorials by Barb and Dave Tewksbury available on this site. Other than that, there are no prior skills or concepts.
How the activity is situated in the course
This activity comes early in the course, around the third week of the semester, in a section on tectonics and geomorphology.
Goals
Content/concepts goals for this activity
By the end of this lab students should be able to provide a concrete and specific example of how digital elevation data can be used in ArcGIS to answer a scientific question in tectonic geomorphology.
Higher order thinking skills goals for this activity
Hypothesis generation and testing. Data collection, observation, analysis, and interpretation.
Other skills goals for this activity
Developing GIS skills and some familiarity with LiDAR DEM data. Scientific writing is a subsidiary goal as well.
Description and Teaching Materials
1) In small groups, students are asked to answer these questions:
What happens to the land surface when a major earthquake occurs? How might erosion be effected by faults? How would this erosion be expressed on the landscape? Make a map-view sketch of a strike slip fault segment where part of it moved recently, but other parts did not. What would happen to erosion in the different parts of the fault? Make some hypotheses.
2) This is followed by students downloading the GIS data necessary for the exercise (which I provide on a server). I then do a short workshop on the ArcGIS skills they will need to use for the lab. Each student has his/her own computer and I walk them through the techniques. I give them space for notes on this lab write up for this.
3) Students get comfortable with the ArcGIS measure tool by measuring stream offsets and making an estimate of slip rate. This part of the lab is optional and I have skipped it completely. It is available here for completeness' sake.
4) We then re-group and have another discussion. I ask them, in small groups, to answer this question:
How can slope profiles be used to say something about the timing of motion on the SAF?
After the small group discussion, we come back together and we collectively develop a methodology whereby we can use detailed slope profiles across the SAF to ascertain the timing of motion (relative). They must keep track of the methodology we collectively have developed, then they apply the methodology to their GIS and LiDAR dataset.
5) Students are required to submit a map and a lab write up that summarizes their hypothesis, results, and interpretations.
Lab Write Up/Hand out (Microsoft Word 2007 (.docx) 410kB Jun9 14)
All GIS data (Zip Archive 643.4MB Jun9 14)
What happens to the land surface when a major earthquake occurs? How might erosion be effected by faults? How would this erosion be expressed on the landscape? Make a map-view sketch of a strike slip fault segment where part of it moved recently, but other parts did not. What would happen to erosion in the different parts of the fault? Make some hypotheses.
2) This is followed by students downloading the GIS data necessary for the exercise (which I provide on a server). I then do a short workshop on the ArcGIS skills they will need to use for the lab. Each student has his/her own computer and I walk them through the techniques. I give them space for notes on this lab write up for this.
3) Students get comfortable with the ArcGIS measure tool by measuring stream offsets and making an estimate of slip rate. This part of the lab is optional and I have skipped it completely. It is available here for completeness' sake.
4) We then re-group and have another discussion. I ask them, in small groups, to answer this question:
How can slope profiles be used to say something about the timing of motion on the SAF?
After the small group discussion, we come back together and we collectively develop a methodology whereby we can use detailed slope profiles across the SAF to ascertain the timing of motion (relative). They must keep track of the methodology we collectively have developed, then they apply the methodology to their GIS and LiDAR dataset.
5) Students are required to submit a map and a lab write up that summarizes their hypothesis, results, and interpretations.
Lab Write Up/Hand out (Microsoft Word 2007 (.docx) 410kB Jun9 14)
All GIS data (Zip Archive 643.4MB Jun9 14)
Teaching Notes and Tips
This lab requires a lot of interaction between the instructor and the students. The instructor must scaffold the exercise effectively such that the methodology the students will use is relatively clear. There is a lot of confusion and the inevitable ArcGIS bug problems that pop up randomly, so one must have good facility with the software. I essentially see this exercise as a combination of a GIS workshop and a fundamental exercise on tectonic geomorphology.
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Assessment
They are assigned a grade on their lab write up. I typically use a standard paper grading rubric.
References and Resources
Source for LiDAR data:
http://www.opentopography.org/
http://www.opentopography.org/