Sandy Hollow Virtual Field Geology Exercise

Andrew K. Laskowski, Montana State University-Bozeman

Devon A. Orme, Montana State University-Bozeman

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Summary

This is a Google Earth based virtual field exercise focused on Sandy Hollow, near Block Mountain and McCartney Mountain in southwest Montana. This is a classic field locality in the Montana portion of the Sevier fold-thrust belt. For more information on the area, the reader is referred to Chapter 6: Geology of Southwest Montana in Guidebook to the Geology of Central and Southern Idaho by Paul K. Link and William R. Hackett, available as a PDF from the Idaho Geological Survey.
Exercise 1 "Sandy Hollow: Stratigraphy" is a guided exploration of the Permian—Cretaceous stratigraphy at Sandy Hollow, including the Permian Phosphoria Formation, the Triassic Dinwoody Formation, the Cretaceous Kootenai Formation (members 1-4), and the Cretaceous Colorado Group (Blackleaf Formation). Students are tasked with construction of a representative graphic log of these units based on geo-referenced YouTube videos and GigaPan images embedded in Google Earth.
Exercise 2 "Sandy Hollow: Mapping" is a map project that tasks students with creating a hand-drawn geologic map of Sandy Hollow based on provided geo-located bedding measurements and rock unit identifications. Contact locations are informed by color changes that are clearly visible in Google Earth imagery. An embedded YouTube video introduction filmed on location is provided.
Exercise 3 "Sandy Hollow: Structural Analysis" is a stereonet-based project that asks students to compare the orientation of cleavage with the orientation of the axial plane of a major fold in Sandy Hollow. Students create two stereonets, one showing cleavage orientations as poles and another showing bedding orientations, the fold axis, and the orientation of the axial plane (π-diagram). This process requires synthesis of provided structural measurements and the geologic map (specifically, the axial trace) generated by the students in Exercise 2. Exercise 3 was informed by a MS thesis by Elizabeth A. Helmke at Montana State University.

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Context

Audience

This series of three exercises is a virtual (i.e. web-based) version of a multi-day exercise conducted by Geology Field Camp students at Montana State University.

Skills and concepts that students must have mastered

The educational level of participants is upper-division undergraduate students who have completed their core courses in a Geology or Earth Science major. Students are expected to understand concepts of sedimentology and stratigraphy, structural geology, and field methods at the level of a senior undergraduate student. These courses (if offered) should be completed by students prior to attempting these exercises.

How the activity is situated in the course

This activity is situated as the final virtual field exercise in this year's online Geology field camp at Montana State University.

Activity Length

I have scheduled a total of five days for this activity, two for Exercise 1, two for Exercise 2, and one for Exercise 3. I expect students will spend 4-5 hours per day on this activity.

Goals

Content/concepts goals for this activity

Drafting graphic logs, interpreting depositional environments, linking lithologic observations to tectonics, geologic mapping, structural analysis, use of stereonet plots to conduct structural analysis, linking orientation data to tectonics.

Higher order thinking skills goals for this activity

Analysis of field observations including lithologic descriptions, structural data, and Google Earth imagery, outcrop interpretation, hypothesis testing relating to the comparison of fold axial plane and cleavage orientations.

Other skills goals for this activity

Technical writing for write-up assignments, creation of professional-looking geologic maps, stereonets, and graphic logs, time management, independence, planning, data management, logistical skills including printing and scanning.

Description and Teaching Materials

Each Exercise is a stand-alone KML file that is best viewed in the online version of Google Earth. This program runs in the freely available Firefox and Chrome browsers. If using Chrome, web page preferences will have to be modified to allow "Insecure Content" so that the embedded Gigapan photos load correctly. Alternatively, there is a hyperlink provided to view the original Gigapan source. To launch each exercise, navigate to Google Earth in your web browser (earth.google.com). Click on the "hamburger menu" at the top left of the screen and select "Projects". Under Projects, click the button for "New Project" and select "Import KML file from computer". Click "present" to view the information in the intended order. Instructions for each exercise are provided as a full screen slide within the Google Earth project (KML file). Supplementary files referenced in the instructions are provided in the zipped folder.

This exercise consists of the following files, provided in a zipped folder

Folder: Exercise 1 Stratigraphy
Sandy Hollow Stratigraphy (Exercise 1).kml contains instructions and geo-located YouTube videos and GigaPan photos

graphic_log_template.pdf is a template that students can print to create graphic logs

Example_Log_Symbols.pdf is an example of standard symbols and drafting techniques used in the creation of graphic logs.

Folder: Exercise 2 Mapping

Sandy Hollow Mapping (Exercise 2).kml contains instructions, a geo-located YouTube video introduction, and a collection of 44 points with rock unit identifications and bedding measurements.

MT_Block Mountain_topo_base.pdf is the topographic base map for this mapping exercise.

Legend.pdf is a document with standard geologic map symbols and space for students to draft their own lithologic symbols for each map unit.
Folder: Exercise 3 Structural Analysis

Sandy Hollow Structural Analysis (Exercise 3).kml contains instructions, a geo-located YouTube video, and geo-located cleavage measurements.

AllUnits_bedding.xls is an Excel table of all bedding measurements provided to students in Exercise 2.

Kk2_cleavage.xls is an Excel table of the cleavage measurements from the Kootenai Formation, Member 2, which are also provided as part of the .kml.

lambert-equal-area-stereonet.pdf is a stereonet that students can print to draft their diagrams.

Sandy Hollow Virtual Field Geology Exercise.zip (Zip Archive 10.5MB May19 20)


Technology Needs

Students should have access to a computer capable of running Google Earth online using a free web browser like Google Chrome or Firefox, a printer, a method of scanning to .pdf, drafting pencils and pens, an eraser, colored pencils, tracing paper, and a thumb tack.

Teaching Notes and Tips

KML and supplementary files for each exercise can be distributed to students in a zipped folder or via Learning Management System course page. Video introductions or live tutorials in addition to those provided here may be helpful, but are not necessary.
This collection of exercises can easily be modified. KML files are editable, so instructors can assess any changes they would like to make and edit the instructions accordingly. For a shorter experience, students can complete only Exercise 1, or Exercise 1 and 2. Exercise 3 depends on completion of Exercise 2. The instructions are written assuming that students will submit assignments to a folder on a LMS page. This text should be modified if a different submission method is preferred.

Assessment

Instructors are encouraged to complete these exercises along with the students. Then, student work can be assessed by comparing the student submissions to the work completed by the instructor. Students should be assessed based on whether they successfully interpreted and logged the stratigraphy (Exercise 1), applied geologic mapping skills and principles of geology to complete the geologic map (Exercise 2), and synthesized structural data to determine whether the cleavage and fold axial plane orientations are similar or different (Exercise 3). Published maps are available for the area, and links are provided below for relevant geological context.

References and Resources

Helmke, E. A., 2008, Structural Analysis of Cleavage at Sandy Hollow, McCartney Mountain Fold-and-Thrust Salient, Southwest Montana [M.Sc. thesis]: Bozeman, Montana State University, 131 p.
Link, P. K. and Hackett, W. R., 1988, Guidebook to the Geology of Central and Southern Idaho, Moscow, Idaho, Idaho Geological Survey, 319 p.


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