Cutting Edge > Courses > Hydrogeology > Hydrogeology, Soils, Geochemistry 2013 > Teaching Activities > Soil Under the Microscope Mini-Workshop

Soil Under the Microscope Mini-Workshop

Steven Driese, Baylor University

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This page first made public: Jun 6, 2013

Summary

This mini-workshop is a brief introduction to the use of the polarized light microscope for thin-section analysis of soils, known as micromorphology. It assumes only a rudimentary knowledge of mineralogy and sedimentary petrology. Participants have an opportunity to describe and characterize soils with different properties in thin section. Applications to environmental geology and hydrogeology are also mentioned.

Context

Audience

This type of activity is incorporated into three courses at Baylor University: GEO 4373 Global Soil Systems, which is offered for undergraduates as an upper-level elective, as well as first-year graduate students (one lab). It is also used in GEO 5340 Paleopedology, a graduate course (one lab). The activity dominates in GEO 5342 Paleopedology of Soils and Paleosols, a graduate course, where it is used throughout the semester.

Skills and concepts that students must have mastered

Students should have had a basic introduction to the use of the petrographic (polarized light) microscope, as well as to the examination of the optical properties of minerals in thin section.

How the activity is situated in the course

It is used a part of a sequence of exercises in all three courses.

Goals

Content/concepts goals for this activity

To understand that thin-section microscopy can be applied not only to the study of rocks, but also to study of soils.

Higher order thinking skills goals for this activity

Synthesis of ideas reagrding the basic components of soils observable in soils, and the interpretation of pedological components as related to soil genesis and classification.

Other skills goals for this activity

Operating a polarized light microscope, recording basic soil micromorphological observations.

Description and Teaching Materials

Instructions for "Soil Under the Microscope" Mini-Workshop (classroom-based):

A. Soil Under the Microscope:

a. Participants first review the Power point (2002) prepared by Hari Eswaran (USDA) and Richard Drees (Texas A & M Univ., deceased) entitled "Soil Under the Microscope" – this is a 22 Mb file that is available from the USDA-NRCS at: http://soils.usda.gov/use/worldsoils/microscope/

(note: I had secured Richard's permission to freely disseminate the file.)

b. Review the preceding abbreviated notes on the basics of soil micromorphology (Resource entitled: "Soil Under the Microscope") and Driese's Power point (Resource entitled: "Soil Under the Microscope: A Micromorphology Primer")

c. Each participant is to examine one of the soil thin sections provided (either Tupelo Series Alfisol sampled from 6500 yrs BP floodplain in southeastern Tennessee, the >100,000 yr (and possibly even >1-4 Ma) Dewey Series Ultisol formed on Cambro-Ordovician bedrock in eastern Tennessee, or and Pledger Series Vertisol sampled from 6500 yrs BP floodplain in southeastern Texas), and using the thin-section description sheet provided, prepare a brief description of the pedological features.

Group discussion:Individual participants are asked to briefly discuss their observations and to compare the characteristic features of the 3 different soils (they are very different), having them discuss their philosophy used in describing the soils and what soil-forming factors influenced soil genesis, and in turn, micromorphology. Optional: Consider the size and distributions of the pore structures (areas filled with epoxy) and discuss how they would affect hydraulic conductivity and contaminant transport in these soils

link to 2002 Eswaran and Drees Powerpoint presentation: "Soil Under a Microscope: Evaluating Soils in Another Dimension"

http://soils.usda.gov/use/worldsoils/microscope/

Soil Micromorphology Power point (PowerPoint 13.3MB May15 13)
Student handout for Soil Micromorphology (Microsoft Word 2007 (.docx) 2MB May15 13)
2002 Power point by Esawaran and Drees (PowerPoint 21MB May15 13)
Driese's GEO 5342 Syllabus for course taught at Baylor University (Microsoft Word 2MB May15 13)

Teaching Notes and Tips

Students should be instructed on proper "etiquette" regarding handlind of student polarized light microscopes. If you have attached digital cameras they may need instruction on how to acquire images. Finally, safe handling of thin sections is a priority.

Assessment

Students are assessed by providing them with an "unknown" sample and asking them to describe and interpret the soil (or paleoso) as completely as they can, given no "contextual" infomation.

References and Resources

See http://www.youtube.com/watch?v=-T2luwLcfeg for a bit of humor to start

Eswaran and Drees (2002) provide an excellent introductory Power point presentation on the microscopic study of soils "Soil Under a Microscope" that is available from the USDA-NRCS at: http://soils.usda.gov/use/worldsoils/microscope/

Inexpensive Resource:
Stoops, G., 2003, Guidelines for Analysis and Description of Soil and Regolith Thin Sections: Madison, WI, Soil Science Society of America, 184 p. + CD w/images. (This is very reasonably priced (at $40) but definitely not very exciting book that has a great CD with photomicrographs, and has a very comprehensive reference list.)

Recommended New Resource ($$$$):
Stoops, G., Marcelino, V., and Mees, F. (eds.), 2010, Interpretation of Micromorphological Features of Soils and Regoliths: Amsterdam, Elsevier Pub. Co., 720 p. (spectacularly illustrated newest text with lots of beautiful color images, organized as topical Chapters, each authored by experts; unfortunately, at a price of $210 from Amazon.com, probably out of reach for most faculty and students: get your library to purchase it!)

Other Useful Resources:

Blokhuis, W.A., Kooistra, M.J., and Wilding, L.P., 1990, Micromorphology of cracking clayey soils (Vertisols), in Douglas, L.A., (ed.), Soil Micromorphology: A Basic and Applied Science: New York, Elsevier Pub. Co., Developments in Soil Science 19, p. 23-148.

Brewer, R., 1976, Fabric and Mineral Analysis of Soils, 2nd edition: Huntington, New York, Robert E. Krieger Publishing Co., 482 p. (Considered "the Bible" of micromorphology by many, but employs a rather dense terminology and is out of print!)

Bullock, P, Fédoroff, N., Jungerius, A., Stoops, G., Tursina, T., and Babel, U., 1985, Handbook for Soil Thin Section Description: Wolverhampton, UK, Waine Research Publications, 152 p. (Great book by group of experts, but out of print!)

Cady, J.G., Wilding, L.P., and Drees, L.R., 1986, Petrographic microscope techniques, in Methods of Soil Analysis, Part I. Physical and Mineralogical Methods: Soil Science Society of America, Monograph No. 9, p. 185-218.

Delvigne, J.E., 1998, Atlas of Micromorphology of Mineral Alteration and Weathering: Mineralogical Association of Canada, Canadian Mineralogist Special Publication 3, 494 p.

Douglas, L.A., and Thompson, M.L. (eds.), 1985, Soil Micromorphology and Soil Classification: Madison, WI, Soil Science Society of America Special Publication No. 15, 216 p.

Drees, R., and Ransom, M.D., 1994, Light microscopic techniques in quantitative soil mineralogy, in Quantitative Methods in Soil Mineralogy: Madison, WI, Soil Science Society of America Miscellaneous Publication, p. 137-176.

Eswaran, H., and Drees, R., 2002, Soil Under a Microscope: Evaluating Soils in Another Dimension: College Station, TX, Texas A & M University, Department of Soil & Crop Science (21 Mb Powerpoint Presentation, 79 images, at: http://soils.usda.gov/use/worldsoils/microscope/

Fitzpatrick, E.A., 1993, Soil Microscopy and Micromorphology: New York, John Wiley and Sons, 304 p. (Excellent book, perhaps even "the best", unfortunately out of print!)

Kubiëna, W.L., 1938, Micropedology: Ames, Iowa, Collegiate Press, Inc., 243 p. (a "classic" by the "Founding Father" of soil micromorphology, and obviously out of print!

Nettleton, W.D. (ed.), 1991, Occurrence, Characteristics, and Genesis of Carbonate, Gypsum, and Silica Accumulations in Soils: Madison, WI, Soil Science Society of America Special Publication No. 26, 149 p.

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