Scaffolding Temporal Reasoning with Geologic Timelines

Introductory physical geology course for non-majors

There are no requisite skills or concepts. Students should work with a partner with whom they are comfortable since views of human history may have a strong cultural basis.

This activity is the beginning of the unit on geologic time.

The content goal of this activity is for students to recognize how recently humans appeared relative to the vastness of geologic time. Additionally, the events included in the geologic timeline are selected to call attention to how long it took for vertebrates, land plants, and dinosaurs to appear in the geologic record. Students are not expected to memorize these dates, but instead to gain a sense of temporal scale.

Students are expected to commit to a hypothesis regarding the order of events from geologic history. Through discussion with their partner, they must come to a consensus about how they will order and space the events on their physical model. They then must evaluate how their model compares to the scientific consensus model.

Prior to the activity, students participate in an individual clicker question administered to the class. The image file contains a geologic timeline where students are asked to click where they think humans appeared on Earth. Then they are asked where they think dinosaurs appear on Earth. The image file was uploaded to Top Hat, a web-based student response system, which offers click-on-diagram questions. Several other companies offer this style of question. Students were asked the question before the activity to commit to a prediction. This approach is part of the Predict-Observe-Explain inquiry cycle described by White and Gunstone, 1992.

Next, students were asked to discuss their prediction with their partner and come to a consensus on the worksheet about where humans and dinosaurs appear on the timeline. This helps students discuss their naïve views on geologic time and identify common points of confusion. The pairs are then asked to complete the worksheet together, including placing sticky note flags on a meter stick indicating the order and spacing of geologic events. The order and spacing of geologic events are done separately because Libarkin, Kurdziel, and Anderson (2007) identified that college students were generally better at the ordering of geologic events than the timing or scale of those events.

Once the students have placed all of the labeled tags on their meter stick, they receive a piece of paper printed with the accurate order and spacing of scientific consensus model. The students attach this paper to their meter stick and compare where their model is similar and diverges from the scientific model. This approach provides feedback to the students to facilitate changes to their mental model. This constructivist approach stems from Piaget's idea of accommodation.
Geologic Time Worksheet (Microsoft Word 2007 (.docx) 44kB May31 17)

The implementation of this activity is important. Students need to commit themselves to a prediction individually, then with their partner, then use the steps in the activity to iterate and enhance their physical model. Once students have committed the order and spacing of events on their meter stick, they should get a printed poster of the scientific consensus timeline. Print the .jpg on a plotter and laminate it for durability. Use Velcro tabs on the meter sticks and timeline poster to attach them easily. If you choose to do a clicker question with the timeline before and after this activity, an image file is provided.

The activity worksheet was graded for completeness because this particular course required participation, but not perfection, in in-class activity. The instructor reviewed students' responses to question 5, which asks students to describe differences in the order and spacing of their events.
Assessment of individual temporal reasoning was conducted after the activity. Students were individually asked to place the appearance of humans and dinosaurs on a timeline using a clicker question. This showed that some students still retained relatively poor sense of scale for the appearance of dinosaurs, although their conceptual understanding of the recentness of human history was firmly in place.

This activity is based on the Roping Geologic Time activity in the Exemplary Collection by Randy Richardson: https://serc.carleton.edu/NAGTWorkshops/time/activityposter/11585.html The current activity enhances Roping Geologic Time because each student participates with the physical model directly.

The printable .jgp for the timeline that can be attached to a meter stick was designed by Mark Howland, Geology, Norther Illinois University