Weathering of Igneous, Metamorphic, and Sedimentary Rocks in a Semi-Arid Climate - An Engineering Application of Petrology

Wendy J. Harrison and Richard F. Wendlandt

Colorado School of Mines

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Initial Publication Date: June 8, 2008 | Reviewed: June 7, 2013 (see revision history: 2 events)

Summary

Students examine soils developed on igneous, metamorphic, and sedimentary rocks near Denver, Colorado. The 2-week exercise includes sample collection, description, and preparation, determining clay mineralogy by XRD, and measurement of Atterberg Plasticity Indices. This problem develops skills in X-ray diffraction analysis as applied to clay mineralogy, reinforces lecture material on the geochemistry of weathering, and demonstrates the role of petrologic characterization in site engineering.

Geochemical Analysis, X-ray Techniques, Volcanology, Geochemistry, ...(more) | College Lower (13-14), College Upper (15-16)

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Context

Audience

This exercise is used in a sophomore or junior level required course in petrology.

Skills and concepts that students must have mastered

Students should have an understanding of basic physical geology, mineralogy, petrology, and XRD.

How the activity is situated in the course

This activity is a 2-week project.

Goals

Content/concepts goals for this activity

This problem develops skills in X-ray diffraction analysis as applied to clay mineralogy, reinforces leacture material on the geochemistry of weathering, and demonstrates the role of petrologic characterization in site engineering.

Higher order thinking skills goals for this activity

This activity involves analyzing data.

Other skills goals for this activity

This activity involves writing and the operation of analytical equipment.

Description of the activity/assignment

The identification of clay mineral assemblages in soils provides a unique opportunity to demonstrate how basic principles of petrology and geochemistry are applied to engineering design criteria in construction site preparation. Specifically, the problem investigates the conditions leading to the formation of smectite in soils and the resulting construction risk due to soil expansion. Students examine soils developed on igneous, metamorphic, and sedimentary rocks near Denver, Colorado. The field locations are areas of suburban growth and several have expansive soil problems. The 2-week exercise includes sample collection, description, and preparation, determining clay mineralogy by XRD, and measurement of Atterberg Plasticity Indices. This problem develops skills in X-ray diffraction analysis as applied to clay mineralogy, reinforces leacture material on the geochemistry of weathering, and demonstrates the role of petrologic characterization in site engineering.