Geologic Mapping in a Classroom

Goals

• Simulate the making of a geologic map;
• Integrate information from rock specimens, maps and visual imagery into a geologic history;
• Understand the geologic history of an existing location through study of rocks and existing maps;

Skills

• Measure rock orientations;
• Describe rock specimens;
• Make and interpret geologic maps and cross-sections;
• Interpret air photos and satellite imagery (for some examples;)
• Integrate geophysical and geologic data (for some examples).

This lab exercise is particularly good for bad weather. It is probably most appropriate for the middle or near the end of an introductory geoscience course, once students have some experience describing hand specimens of rocks, interpreting maps, and evaluating data. On the other hand, the parts of the lab can be done over the course of several labs (one to describe the rocks, one to work with the maps, one to examine the geophysical data, etc.) before all the information is integrated into a single geological history.

The lab may be set up in one of two general ways: either an imaginary mapping area can be invented ("Desperation Flats") or a real area can be studied (e.g. the Black Hills of South Dakota). If the latter approach is used, the instructor should acquire the site-specific maps, rock samples, and geophysical evidence (if desired). In the former case, the "field area" can become many different regions, depending on the orientation of the class. It is possible, for instance, to acquire samples that would be found in an area of granite intrusion into sediments, in a fold and thrust belt, in a folded ophiolite sequence, etc.

Steve Reynolds (Arizona State University) has an excellent example of an imaginary geologic site, the Sierra Cobre:
He has created virtual topography for Sierra Cobre, as well as geochemical analyses of copper, a geologic map and cross-sections and well drilling results. Students have a limited budget with which to acquire some of this information.

The University of Leeds - Virtual Mapping Project may be too complex for introductory geoscience, but it can be used as a basic template for constructing something similar.

In its simplest form, the following ingredients are required for a successful "geologic mapping in the classroom" laboratory:

• A base map, without or without topography, that shows the dimensions of the mapping area and some fixed locations (table corners, locations of rock samples, etc.);
• Rock samples for students to describe;
• Written notes, photos or models which students can use to reconstruct bedding orientations or other planar and linear features; (Note: it is relatively simple to orient small masonite rectangles in different orientations on a flat base. Students can then use a compass to measure the orientations themselves. See picture.)
• Written or visual information about contacts, faults and other corss-cutting features;
• If desired, regional geologic maps, geophysical data and/or remote sensing imagery to give the "mapping area" a broader context. (This is particularly important when the goals include introducing students to the geology of a real area, such as the Black Hills.

On the basis of the mapping and rock descriptions students complete in the lab, the follow-up assignments can include a polished geologic map and geologic cross-sections, a set of rock descritpions, a geologic history of the smaller mapping area and a geologic context, derived in part from regional materials.

The sample exercise provided by Steve Reynolds (Arizona State) asks students to evaluate the economic potential of the "Sierra Cobre" copper deposit. Depending on the course, the student assignments can be tweaked to meet such additional aims.

Instructors can assess the written and visual information students produce - maps, cross-sections, rock descriptions, geologic history, etc. - for understanding of the techniques and for sophistication of the interpretations.

Steve Reynolds's (Arizona State University) Sierra Cobre site.

Another potentially useful site is Planet Oit (now offline). "Planet Oit" is part of a virtual reality "Geology Explorer."