Surficial Geologic Mapping and Interpretation from Aerial Photography and Stratigraphic Unit Descriptions

This exercise is completed as part of the laboratory component of an undergraduate course: Field and Laboratory Methods, which is an upper-division geology course that is required for the major. Approximately half of the course focuses on geologic field skills and techniques (e.g., rock/outcrop/formation descriptions, unit identification and mapping, and associated skills) and half focuses on laboratory methods and their geologic applications (e.g., geochronology, stable isotopes, SEM, XRD, XRF, mass spectrometry, etc.). The course typically enrolls junior- and senior-level geology majors and occasional environmental science majors.

Students should have prior experience reading and interpreting topographic and geologic maps, preparing simple geologic cross sections, describing sedimentary rocks, and working with structural data (i.e., strike/dip data). Ideally, students would have completed undergraduate-level courses in (1) sedimentology and stratigraphy and (2) in structural geology prior to taking this course.

This exercise is completed as a stand-alone laboratory project during two laboratory sessions near the middle of the semester. Prior to assignment of this exercise, one lecture session introduced students to the geologic application of aerial photography and other remote sensing data. Additionally, prior lectures and laboratory activities provided experience in describing rocks at the outcrop and formation scale and defining unit contacts, which relates to the application of stratigraphic unit data to interpret unit occurrence/distribution within the project map area.

This exercise provides: (1) experience in evaluating and interpreting features visible within an aerial photograph, (2) additional practice reading and interpreting topographic and geologic maps and associated map symbols, (3) additional experience reading and thinking about rock unit descriptions, (4) additional practice preparing geologic maps and geologic cross sections.

This exercise develops critical thinking skills by comparing rock unit descriptive information to features depicted in an aerial photograph in order to identify, map, and interpret geologic units and structures occurring within the map area.

Each student has the opportunity to further refine her/his skills for preparing professionally drafted figures depicting geologic data/interpretations (i.e., geologic map and cross section).

This activity uses a combination of aerial photography and sedimentary and structural data to remotely identify, map, and interpret the geology of the project field area. The skills learned and developed during this exercise are directly applicable to field geologists and remote evaluation of geology is highly useful in several ways: (1) provides the opportunity to prepare a draft geologic map of a field area from data obtainable from a general literature review, which could then be field-checked for accuracy and revision; (2) provides the option for expanding the geologic mapping of a field area, where, following a reconnaissance field event or small area mapping event, one could extend mapping across a larger area by comparing data obtained during that small scale event to aerial photography of the same area and then extrapolating interpretations to the surrounding area; (3) can be used to more accurately distinguish between and map Quaternary units of differing types and ages; and (4) can assist in locating features within regions of very gentle topography or in areas where topographic contour intervals are insufficiently detailed to allow for highly accurate location on traditional maps.
Student Instructions for Aerial Photo Mapping Exercise (Microsoft Word 2007 (.docx) 93kB Aug11 22) 
Student Figures for Aerial Photo Mapping Exercise (Acrobat (PDF) 16.5MB Aug11 22) 

Instructions for Aerial Photo Mapping Exercise_ANSWER KEY and NOTES -- educator-only file

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Figures for Aerial Photo Mapping Exercise_ANSWER KEY -- educator-only file

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This laboratory project is completed during two laboratory sessions.

Laboratory session 1: To begin this exercise, I display the instructions handout using a projector/screen and I have the students answer the questions in the instruction handout as an interactive group activity. This forces the students to think about the project and allows me to help guide them through the thought process of how they will identify the units and unit contacts. This is particularly helpful because as a small department, my upper division courses are taught on a two-year rotation. Depending on when students entered their major course sequence, there is always a range of background and experience within the class group (i.e., it is possible that this could be an individual's first or last upper division course for his/her major). Once we have worked through the instruction questions as a group, I will leave the students to struggle with their initial unit and unit contact identifications. Students are encouraged at this point to discuss their ideas with their peers. Once the students have initially identified two or more adjacent units and their contact, I will project the aerial photo onto a dry erase board and have student volunteers explain their interpretations and draw the contact between those units on the dry erase board followed by discussion of their interpretations, with revision, as necessary. After this, students generally are able to proceed with identifying the remaining units and contacts with minimal to moderate questions/assistance.

Laboratory session 2: Students may or may not have identified all units and contacts during the first laboratory session. Once their contacts are complete and transferred to the topographic base, they should begin preparing the bedrock geologic cross section. The overturned beds are typically a point of confusion for students. As a group, I will schematically demonstrate (draw on the dry erase board) how a folded and tilted sequence can display those overturned beds due to erosion of that sequence. For students who have not yet completed structural geology (as well as some who have), this will be one of the most challenging parts of the project to visualize. Students work to prepare professionally drafted figures for the remainder of the laboratory session.

Additional instructor's notes are included in the instructor's version (answer key) of the project instruction handout. These additional instructor's notes, where included, are specific to questions or tasks included in the instruction handout.

Students meeting the goals for this exercise will have: (1) correctly identified and labeled the rock units visible within the aerial photograph/map area; (2) successfully identified, located, and traced (drawn) the contacts of the rock units; (3) reasonably interpreted the structure of the rocks occurring within the aerial photograph/map area; and (4) prepared and submitted a complete, accurate, and professionally drafted surficial geologic map, bedrock geologic cross section, and map and cross section key.