Geological Mapping of a Virtual Landscape

Mark Helper, Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin; helper@jsg.utexas.edu

This exercise is based on the Virtual Landscapes Geological Mapping activity developed by Jacqueline Houghton and the University of Leeds Virtual Landscapes team

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Summary

This virtual mapping exercise is part video game, part map prediction and interpretation. You will navigate a virtual landscape to "collect" outcrops and their field notes, recording your observations on a paper base map and in a field book as you go. A pop-up compass and GPS instrument are there to assist your navigation to the outcrops. Having recorded all outcrop data on the base map and compiled the field notes, you'll have what you need to complete a geologic map and a stratigraphic column. Making a geometrically sound map from the very limited outcrop data is a challenging (and realistic) task. To do it correctly you'll also incorporate Rule of V's concepts and strike lines. The outcome of the exercise is a completed geologic map, a map key, and a properly order stratigraphic column with rock unit descriptions.

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Context

Audience

This virtual mapping exercise was built to replace an introductory weekend field mapping exercise when the Spring 2020 COVID-19 pandemic prevented taking students to the field. It is one of six weekend field exercises for a required, sophomore-level, Introduction to Field and Stratigraphic Methods class for geoscience majors.

Skills and concepts that students must have mastered

Students at this point know how to use a compass, are familiar with strike and dip, know how to read a topographic map, and can write and understand sedimentary rock descriptions. They have also learned to plot GPS coordinates on a gridded base map. A week prior to this exercise, they began working in lab with simple synthetic geologic maps to better understand the rule of V's and how to draw and use strike lines to calculate strike and dip. The latter were presented via several map examples in two lectures that immediately preceded the exercise.

How the activity is situated in the course

This is the first of three weekend mapping activities for a 4-credit hour introductory field course. Like the real thing, mapping this relatively simple geology (a single panel of uniformly dipping rock units) as a starting point for later exercises can build confidence and be used to address conventional, mundane map-making issues (orienting a map, plotting measurements, drafting, labeling, etc.) that otherwise take time away from more interesting and difficult aspects (multiple working hypothesis testing, traverse strategies, etc.). Later exercises can build on these skills and this new-found confidence. Students at this point have completed three weekend exercises focused on section measuring, sketching, and sequence stratigraphic concepts/rock unit correlation but have not done any mapping.

Activity Length

This activity takes 1.5 to 2 days.

Goals

Content/concepts goals for this activity

  1. How to use strike & dip, rule of V's and strike lines to test mapping hypotheses.
  2. How to use a map and limited field observations to reconstruct a stratigraphic record.
  3. How to complete a simple geologic map from a limited amount of observational data.

Higher order thinking skills goals for this activity

  1. Develop a sense of how geologic outcrop mapping proceeds, from studying base maps to derive a field strategy, to "flexecuting" and modifying the strategy in the field as new information is obtained.
  2. Begin to understand how to make mapping predictions when building a map from limited field data.

Other skills goals for this activity

  1. How to record field data on a base map - rock types with colored pencils, strike & dip and contacts with symbols, use of GPS coordinates
  2. How to use a compass and topographic map to navigate
  3. How to prepare (draft, symbolize, annotate, label) a geologic map from field data

Description and Teaching Materials

Instructors and students should begin by viewing the "Summary of Lighthouse Bay..." document, which contains general and more specific information necessary to complete the exercise. Next, view the student handout for this exercise, which contains detailed instructions, examples, thought questions and advice for completing the exercise. Also attached are: 1) the 1:5000 scale topographic base map (suitable for printing on letter size 8.5x11" paper) needed for mapping and 2) a presentation containing a schedule for remotely teaching the exercise and an animation that shows how a single strike and dip measurement can be used to extend rock unit contacts via strike lines. An answer key is also attached. Finally, a short video shows how to use strike lines to build a map from limited data. As is stated in the attached documents, the Lighthouse Bay exercise builds upon the University of Leeds Virtual Landscapes (https://www.see.leeds.ac.uk/virtual-landscapes/) Lighthouse Bay geological mapping exercise, available for use under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International Licencse. As required, the materials being posted here are distributed and shared under the same license.

Technology Needs

Mac or PC with Google Chrome Browser. Easiest to operate with a mouse, but can be done with keyboard and touchpad.

Teaching Notes and Tips

:Please see the included PowerPoint for notes on teaching this material. When taught to groups of 25+ students, the use of Breakout Rooms, each focused on a single question during early portions of the exercise, worked well. Periodic check ins allow resolution of issues. The Virtual Landscape software is amazingly stable on both Macs and PCs. Only 1 student in 54 had any problems. It does not run on mobile platforms. A printed map is handy for this exercise, though the provided PDF base map could be used in graphics software (Ilustrator, etc), provided students know how.

Assessment

Graded work indicates that students can mostly complete this within a day's time (they were given three additional days but some turned it in within a hour of finishing the mapping session), and that some will rigorously construct strike lines to complete a map to perfection, while others seem content to construct a few strike lines and guess. The range of work is about the same as seen on real first field mapping exercises. This is interesting because field logistical issues are not in play, yet results are similar.

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