Bedrock Geology Mapping Exercise

Jim Miller
Dept. of Geological Sciences, University of Minnesota Duluth
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As a final exercise in a course on Geological Maps, students conduct a field mapping of a one square mile area over a weekend. Back in the classroom, students are introduced to ArcMAP and Illustrator, with which they digitally compile their field data and create a geologic map interpretation of the field area. After spending the semester evaluating geologic maps from various terranes, this exercise helps the students to appreciate the factual basis and, more significantly, the importance of interpretation in the creation of a geologic map.

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This exercise constitutes the final exam for the Geologic Maps course (Geol 3000). It is an elective course and currently requires only Introductory Physical Geology as the a prerequisite. We have taught the course for 3 years with class sizes between 14 and 18 students. However, because many early geo-majors tend to struggle with some of the concepts, especially structure, we are considering making this a higher level course and requiring Ig/Met Pet, Sed/Strat and Structure as prereqs.

Skills and concepts that students must have mastered

This being the capstone project for the class, students will have been exposed to the components of geologic maps, mapping techniques, and the relationship between topography and map unit patterns. The field area chosen has four main rock types and some subtle variants. Students may choose to lump or split them into different map units as they see fit, which is the essence of geologic map-making. Outcrop in the field area is sparse (~2%), which is typical for this part of Minnesota.

How the activity is situated in the course

Again, it is the final capstone exercise of the course on Geologic Maps.


Content/concepts goals for this activity

The goal of the activity is to give the students an appreciation of how field data is collected and how important interpretation is in the creation of geologic maps.

Higher order thinking skills goals for this activity

During the 12 hours or so that the students are mapping (in field parties of 2-4), they have to strategize about how to use their time most efficiently. Knowing that the most important goal is to establish the locations of geologic contacts, they need to use the structural information they collect to guide them on where to seek out more outcrop that will accomplish that goal.

Other skills goals for this activity

Students develop or hone several other skills in the exercise:
  • measuring structures with a Brunton compass
  • recording complete lithologic information in their notebooks
  • locating themselves on topographic base maps by topography and UTM coordinates determined by GPS
  • learn enough ArcMAP and Illustrator "to be dangerous"

Description of the activity/assignment

This field mapping and map-making exercise is a capstone project for a course on Geological Maps. Over a weekend (~12 hours of field work), students collect lithologic and structural data from outcrops scattered over a one square mile area. Back in the classroom, students digitally compile their field data (outcrop, structure measurements, traverse locations) into ArcMAP. They infer geologic linework (faults and contacts) and units from this data in ArcMAP and then export these data layers into Illustrator. In Illustrator, they add ancillary map components (a cross section, description of map units, correlation diagram, map symbol legend,...) to create a final map at a 1:10,000 scale. Their maps are printed out on 11"x17" paper and saved as a pdf file. This exercise helps the students to appreciate how field data is collected and how these geologic facts are interpretively organized into a four-dimensional picture that is a geologic map.

Determining whether students have met the goals

Student are required to turn in:
  • pdf of their final map
  • all ArcMap files
  • field notebook
  • field map
These components are graded using a rubric.

More information about assessment tools and techniques.

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