Bedrock map of Cliff Island, Casco Bay, Maine

Dykstra Eusden, Bates College


Students collect gps locational and strike and dip data on a day-long fieldtrip to Cliff Island. The data is then used in ArcGIS to make a bedrock geologic map of the island. The final map is exported from Arc and prepared in Adobe InDesign as a tabloid size poster.


Type and level of course
200-level ("sophomore") GIS course taught jointly with environmental studies and geology. One intro geo course or e.s. course as a pre-req. Not required for the geo or e.s. major, but can be used to fulfill a 100- or 300-level geo course.

Geoscience background assumed in this assignment
None, we explain the rocks to the non-geo majors, and have geo majors team up to work with non-geo majors in groups of 2.

GIS/remote sensing skills/background assumed in this assignment
Basic knowledge of ArcMap and ArcCatalog.

Software required for this assignment/activity:
ArcCatalog and ArcMap 9.3 with spatial analyst, DNRGarmin 5.4.1, and Adobe InDesign v. CS4

Time required for students to complete the assignment:
Two weeks including an all day Sunday fieldtrip via ferry to Cliff Island


GIS/remote sensing techniques students learn in this assignment
Students learn how to use the GPS and download data using DNRGarmin. Students learn how to draw polygons and convert them to polylines using the topology tools. Students learn how to plot strike and dip symbols and label them. Students learn basic InDesign skills to make their final map/poster.

Other content/concepts goals for this activity
Students learn how a geologic map is made and displayed.

Higher order thinking skills goals for this activity
Students evaluate the relative ages of the rocks. Students grasp the meaning of "geologic control" with respect to drawing a map.

Description of the activity/assignment

Students collect strike ad dip and gps data on some tilted high-grade Ordovician metasedimentary rocks and a few Mesozoic cross cutting basalt dikeson Cliff Island in Casco Bay, Maine. They then make a map in ArcGIS, finally exporting it to Adobe InDesign to make a "publication" quality bedrock geologic map. The map includes a legend, scale, and a photo gallery of the rocks mapped.

Determining whether students have met the goals

We determine whether students have met the goals based on their finished map, their progress in ArGIS and InDesign work, and their productivity/partcipation in the field collecting the primary data.
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