Teaching about Time

Kathleen Gilbert, Geosciences Department, Wellesley College

I have been teaching labs for the introductory geosciences courses at Wellesley College for the last 10 years. We use a team approach in developing our lab curriculum, which we find very effective. My colleague, Maria Waller, will also be attending this conference. Recently we have been revising and updating our lab curriculum as well as our teaching methods. I am excited to incorporate what we learn from this conference into this process.

Most of our students come to our intro courses with very little geosciences background. Many of them take these courses to fulfill a distribution requirement. However, these courses also serve as the entry into the major, and so we are often conflicted about how to approach teaching many concepts, including geologic time.

We have found that you can't teach the students about time without getting them to understand first that things can change. They have a tough time understanding that a very solid piece of granite could ever break down, that a river could erode a landscape; that things that just seem so present could ever not be there. In addition to having little background in geosciences, our students are also inexperienced and often unfamiliar with much of the natural world.

Much of my own learning and understanding about time has come through work done in the field. Spending time on outcrops that have recorded various events, spending time in modern environments to observe what types of features exist, comparing those modern environments to what I see in the rock record; all have been helpful in my own understanding.

To give the intro students some similar types of exposure, we take them to look at outcrops and glacial deposits, show them videos of modern environments that they may not be familiar with, create simulated field sites within the lab, have them study depositional environments, and work with geological maps.

I find that our field trips are the most effective way for students to begin to adjust their thinking about the earth being static. When the students see differential weathering and cross-cutting relationships, for example, they have a chance to see how a solid piece of bedrock can be altered.

Our activities that focus on teaching deep time deal mainly with unraveling the geologic history of sequences of rock. The students make rock, mineral, and fossil identifications to determine rock formations and depositional environments. We ask them to use these data to make interpretations on how the environment has changed over time. They use the fossil identifications to broadly determine the age ranges for each formation. We have found that the students struggled both with understanding the processes behind the environmental change as well as comprehending the amount of time over which these events occur. The addition of a lab focusing on depositional environments prior to the geologic time lab has been quite effective. We have also found that the students' understanding of the processes involved in this rock sequence improved considerably by showing them photos of the field location before they began the exercise. It's not as good as an actual field trip, but it did work surprisingly well to give them the context that they were missing.

I am very interested to learn from others who have done more with the conceptual part of long periods of time. I am hoping that as I increase my understanding of what methods are effective, I can work with my colleagues to develop labs that will be able to teach these concepts to intro students effectively.