From Ocean Topography to Flexural Rigidity

Andrew Newman
School of Earth and Atmospheric Sciences
Georgia Institute of Technology
Atlanta, GA 30332
Author Profile
  1. This activity was selected for the On the Cutting Edge Exemplary Teaching Collection

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    This resource was reviewed as part of the May 2009 MARGINS Mini-Lesson Workshop. Each activity received verbal feedback from two participants who had reviewed the activity and activity sheet using these guidelines. Authors revised the activities and activity sheets in response to these comments during the workshop.

This page first made public: Apr 28, 2009


The project is designed to engage students in utilizing the ever-improving bathymetric techniques and data available in GeoMapApp to explore the strength of the oceanic lithosphere as a function of age. Because the data includes both satellite and ship track derived solutions, students have the opportunity to see the utility of each, and travel virtually the world's trenches in search of topographic features. Because not all trenches have pronounced forearc bulges, many are complicated by other topography (e.g. seamounts), and the choices of subduction boundaries are numerous, the module will give students the opportunity to explore quite independently, learning many of the pitfalls of 'real-world' science. This module is designed for upper-level undergraduates taking an Introduction to Geophysics or Quantitative Tectonic-type course.

Learning Goals

The students should use critical thinking to analyze the data and synthesize ideas to test the given models of flexural strength. Refer to assessment for details.

Context for Use

This could be a laboratory or homework assignment for upper-level undergraduates taking an Introduction to Geophysics or Quantitative Tectonic-type course. Additional information is provided in the teacher's document that will make the course more approachable for lower-level courses.

Students should be able to develop graphs, and optionally perform line-fitting of datasets.

Description and Teaching Materials

One preliminary assignment file is included. It contains the website for geomapapp which is the only program necessary. Preliminary Assignment handout (instructor version to be modified). (Microsoft Word 1.5MB Sep17 09)

Teaching Notes and Tips

Testing has been very minimal, and a comprehensive teacher's document including suggested locations to make additional calculations is necessary. At present, a few locales, including Peru, Northern Japan, Western and Eastern Aleutians appear sufficient, yet calculations are still necessary.Teachers Document (Microsoft Word 4.1MB May29 09)


What do we want students to know?
- How bathymetry is measured (ship-based and satellite).
- Concept of flexural rigidity and the strength/thickness with age relationship of oceanic lithosphere.
- The value of using proper/SI units and the pitfalls of problems ignoring conversion.
- Spatial comparison of flexural bulge: the existence of, and the spatial variability with relation to plate age and other phenomena
- Concept of error in measurement, interpretation, and modeling.

What do we want students to be able to do?
- Apply simple algebra to real-earth science problems.
- Generate bathymetric profiles and spatial recognition of features and noise.
- Plotting data and reapplying mathematic equations to interpret non-linear relationships.

References and Resources

Information relating to the equations and scientific background for this problem set can be found in Turcotte and Shubert's, Geodynamics, 2nd Edition, Cambridge University Press, 2002.