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Innovative Approaches to Teaching Sedimentary Geology, Geomorphology, and Paleontology
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Cutting Edge > Sedimentary Geology > Sedimentology, Geomorphology, and Paleontology 2014 > Teaching Activities > Exploring topographic steady-state in Taiwan

Exploring topographic steady-state in Taiwan

Karen Gran, University of Minnesota-Duluth
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Summary

This activity is designed as both an introduction to GIS and an exploration of topographic steady-state. Students analyze DEMs from Taiwan to extract topographic profiles across the range. They reconstruct a series of datasets presented in Stolar et al., (2007), showing the progression of the range to steady-state as a space-for-time substitution from south to north. Students are expected to relate their observations from the topography to theoretical concepts discussed in class including accretion and uplift, steady-state, and critical wedge theory.

An extension involves developing a simple numerical model in Excel of a mountain range as it progresses to topographic steady-state landscape, allowing students to investigate the rise of a mountain range to steady-state both from Taiwan data and from their numerical model.

Context

Audience

I use this in an upper-level geology elective course in tectonic geomorphology, although it could also be used in a geomorphology class. The students are generally a mix of junior and senior majors and graduate students (M.S.). This is the first lab for the course.

Although this exercise as it is written is for an upper-level class, it could be easily adapted for lower-level classes through the choice of questions to investigate during the data synthesis half of the lab.

Skills and concepts that students must have mastered

I assume the students have a working knowledge of Excel, including how to make plots. Although this lab is GIS-based, it is written for the GIS novice. Pre-requisites for the class include either geomorphology or sedimentary geology & stratigraphy and calculus, although calculus is not required for this exercise.

Concepts covered in class before we do this lab include basic models for accretion and uplift, theories of mountain range development, and concepts of dynamic steady-state. We usually cover critical wedge theory before the second week of this lab, but it is not an essential component of the lab.

How the activity is situated in the course

This is the first lab for the course. It introduces the use of GIS for simple data extraction from digital elevation model (DEM) datasets. It is designed to explore in more detail the concept of dynamic steady-state. I run this as a two-week lab, with data extraction during week 1 and data synthesis in week 2. I make the lab write-up due after week 3's lab in which we do a simple numerical model of range accretion and uplift. I encourage the graduate students, in particular, to relate their numerical model to their results from this lab in the write-up. One could make this a three-week lab and formally include the numerical modeling component as part of the same lab write-up.

Goals

Content/concepts goals for this activity

Concepts of topographic steady-state in mountain ranges
Accretion, uplift, and erosion

Higher order thinking skills goals for this activity

Synthesis of a large dataset
Evaluation of theoretical concepts in a real mountain range

Extension (with numerical model): Numerical modeling and comparison and evaluation of competing approaches (numerical modeling vs. DEM analyses)

Other skills goals for this activity

Basic ArcGIS
Data plotting in Excel
Paper writing
Analyses of group datasets
Contributing to a group dataset, with the inherent responsibility that comes with knowing others will be relying upon your data.

Description and Teaching Materials

There are 5 files attached. The first is the activity I hand students for week 1. The second is the activity I hand them for week 2 (data synthesis and report writing). The third is the numerical modeling activity we run in week 3 (optional extension). This was originally written by John Swenson at UMD. The fourth file has my notes on how to run the labs, including class notes on building a simple model of accretion and uplift with an elevation-dependent erosional response. The fifth file is a zip file with the shapefile for the 10km wide swaths across Taiwan. The DEM itself can be obtained online at https://lta.cr.usgs.gov/GTOPO30 (as of June 2014). This version of the lab is written for ArcGIS 10.2.

Student handout for data collection (week 1) (Microsoft Word 2007 (.docx) 958kB Jun7 14)

Student handout for week 2 (Microsoft Word 2007 (.docx) 17kB Jun7 14)

Numerical model extension (Microsoft Word 2007 (.docx) 61kB Jun9 14)

Instructor Notes (Microsoft Word 2007 (.docx) 881kB Jun9 14)

Taiwan swath shapefile (Zip Archive 4kB Jun9 14)

Teaching Notes and Tips

See the above file with instructor notes for more details.

This is run as a 2 week lab. During week 1, the students collect data. I divide up the range amongst the class so that each student is responsible for a subset of the data collection and processing. In week 2, they get the group dataset back and have to synthesize the data and answer questions that relate concepts discussed in class (isostasy, accretion and uplift, topographic steady-state, etc.) to the dataset.

An optional extension is to have students construct a simple numerical model with accretion, uplift, isostasy, and erosion and relate that back to their observations from the Taiwan dataset.

Assessment

Students are assessed on technical skills (extracting data from ArcGIS and compiling necessary swath data for the class) in week 1, and their ability to synthesize the group dataset and relate concepts from lecture to the dataset the class gathered in week 2. I have them write a short paper to explain the trends in the data, with calculations and figures to back up their assertions.

References and Resources

Stolar, D.B., Willet, S., and Montgomery, D.R., 2007, Characterization of topographic steady-state in Taiwan. Earth & Planetary Science Letters, v. 261: 3-4, p. 421-431. DOI: 10.1016/j.epsl.2007.07.045.

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