My Geologic Address: Locating Oneself in Geologic Time and Process
In this exercise students find a location, such as school or home, on a series of geologic maps working from small to large scale. Map keys and map features are consulted in order to compose a "geologic address" from the most specific to the most general descriptor.
Maps are selected by the instructor to represent local, regional, and global scales as well as magnetic, gravitational, and tectonic features.
A location on a local geologic map will yield the time horizon of the bedrock as well as its process of formation. Nearby may be a fault zone, cinder cone, glacial deposit, or other notable geologic feature. A regional map may include a thrust belt, basin, or subduction zone, for example. A global map adds larger scale or more distant phenomena to describe in reference to ones location.
Methods of Geoscience Geologic maps are spatial representations of temporal relationships. They codify patterns of interaction and geologic processes across scales in time and space. Interpreting maps, and recognizing the wealth of data they encode in visual fashion, is crucial to geological reasoning.
Context for Use
The exercise takes 2 or 3 hours, depending upon the number of maps referenced. It is intended to acquaint middle and high school earth science teachers with the varieties of maps used to represent geological phenomena. Familiarity with a standard topographic map and its key is a prerequisite.
Description and Teaching Materials
Materials for this activity are eclectic and selected according to geographic location and instructor interest. The basic map is, of course, a local scale geologic one. Maps need to be accompanied by complete description of rock units.
The end product is a geologic address, shared by the student. The following is an example:
Intersection of the Bolton Fault with the Oswego Canyon
Adjacent to outcrop of pillowed lavas
Atop Columbia River Flood Basalt, Wanapum Unit, Miocene Age
In the Tualatin Mountains, the eastern limit of the
Oregon Coast Range, Pleisto-Pliocene uplift
Cascadia Subduction Zone, west of the Cascade Volcanics
On the North American Plate near its collision boundary with the Juan De Fuca Plate.
Different students will note different features at various level of detail. Explanining and clarifying their descriptions of "my geologic address" draws attention to multiple scales for interpreting geologic events and how maps represent such understanding.
Each instructor needs to assemble a set of maps appropriate to location and expertise. I have used this exercise as an exploration prior to field study and as a synthesis after touring and interpreting local sites.
Teaching Notes and Tips
The jargon on map keys is endless. Encourage students to use short quotes, then unpack technical terms as addresses are shared. Working with partners or in small teams is advisable. Maps can be set up as stations, from local to global, then teams rotated from station to station to find their location and relate it to the maps features.
This exercise is intended to promote conversation and dialogue as students share their geologic addresses. For mty teacher education classes, students come from many school districts and hence their addresses represent a number of different local geologic stories–basin sediment, ice age flooding, volcanic eruptions, landslides. As the scale increases, the descriptions become more similar (Cascade Subduction Zone, for example). I have not developed a scoring rubric.
References and Resources
On-line geologic maps are now a potential resource for this activity.