Teaching About Time

Karen Viskupic, Geosciences Department, Boise State University

I am a geologist at Boise State University working to develop a series of online activities about geochronology in partnership with workshop participant Mark Schmitz. We're collaborating with faculty from Boise State's Department of Educational Technology and the Idaho Digital Learning Academy to create learning objects that can be used individually or in series to teach students about relative dating principles, fossil correlation, the geologic time scale, and numerical dating techniques with a focus on U-Pb geochronology. I have a background in U-Pb geochronology and Mark runs a U-Pb lab, so this focus makes sense for us. The goal of the activities is to help students understand why scientists might want to know when Earth events happened and on how we can figure out when they did. The activities will be used in online Earth Science courses for 8^th and 9^th graders in Idaho, but the material could be used in introductory university classes as well. This is my first experience with developing activities for online use.

Mark and I have also led a geologic time field trip for 5^th graders for the past few years. We talk about relative dating techniques at a field location in Boise and then go to Boise State for a lesson on numerical dating techniques and tour of the U-Pb lab. The lab component of the trip includes having each student "date" a model zircon (Ziploc bag with different colored beads that represent ²³⁸U, ²⁰⁶Pb, O, Si, and Zr) by counting atoms to determine the number of half lives that have passed since the zircon formed. Assessment of the activities asks students to draw and explain what they remember from the trip a few days later. Student drawings cover most aspects of the trip including relationships among rocks observed in the field, graphs of parent/daughter vs. time that show half-lives, groups of different colored beads, and mass spectrometers. We do have students make a timeline of their own life and make a timeline for the Earth, but no student has ever drawn this activity in the assessment.

Activities that ask students to scale Earth's history to a sheet of paper or football field or clothesline are often used, but my sense is that these don't work especially well because all the events at the recent end are still too crowded. If we make the scale bigger (perhaps using Google Earth), then the distances get big and I don't think students have a good sense of long distances either. I think what might work better (and I would love to test this...) is to combine both distance and time in the analogy. For example, if the distance is long (maybe 500 miles), students can choose a mode of transportation (or several with different rates—walk, bike, car, train) and calculate not only the distance to events in Earth's history but also how long it would take to get there. Maybe this wouldn't help at all, but given that we often talk about distances in terms of time (e.g. the airport is 20 minutes away) this type of distance plus time analogy might help students make more sense of the vastness of Earth's history. Maybe?