Abstract

Learning about radioactive decay and how rocks are dated is often a challenge for students in introductory geology. Standard laboratory exercises involve studying half-lives by examining changing parent-daughter ratios as an element decays. Several well-known strategies, such as using M&Ms or coins, offer ways to make learning about radiometric dating more fun and relatable. The activity presented here offers a new and unique approach to engage students in learning these concepts as they 'go through the motions' of radioactive decay by playing a variation on the popular lawn game cornhole (aka bean bag toss).

Two-sided bean bags are used as the 'game pieces' of the decay process where the color on one side (e.g., red) reflects the parent material and the color on the other side (e.g., gray) reflects the daughter product. Boxes with dividers that hold the bean bags represent the source mineral crystal (e.g., zircon). Teams of students go through rounds of tossing bean bags into a bucket, where after each round (simulating a half-life), bean bags are placed back into the box in a way that shows the changing ratio of parent to daughter isotopes (by noticing shifts in colors that are 'face up' after successive rounds).

Context

This activity is used in the sequence of labs that focus on dating rocks in introductory non-major geology classes at Georgia State University in downtown Atlanta. The first lab emphasizes relative age dating and has a place-based learning approach. Historic photos of campus buildings are utilized to introduce concepts such as superposition as students arrange photographs in order from oldest to youngest by looking at clues in the images (e.g., hairstyles, cars, and clothing representative of certain decades). The second lab moves into studying absolute age dating and has students go through laboratory activities that build an understanding of the decay process and half-lives. By adding in a kinetic and visual component to the lab, and a popular lawn game played widely in the south, students are more active in building their knowledge. They simulate the decay process and half-lives by tossing bean bags into a bucket and then make observations as to how shifts happen from the parent to daughter isotope all having come from the same material. Calculations students do are based on the ratios they visually 'experience' as part of engaging in this lab exercise.

Why It Works

The approach is effective at engaging students in actively building their knowledge of how radiometric dating works, and breaks down the evaluation of half-lives in a way that allows for visual comparisons as they go. Students still do calculations and study graphs, but they do that alongside the bean bag activity. The gamification of learning about how elements decay through this 'lawn game' strategy is innovative.