Using Melting Ice to Teach Radiometric Dating
Summary
Students are challenged to a Sherlock Holmes-style mystery in which they construct their own decay curves of melting ice to determine time-zero. In the process, the analogies to radiometric dating and some elementary thermodynamics can be discussed.
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Learning Goals
- Explore ice melting as an analogue to radiometric decay.
Context for Use
This activity is appropriate for use in an introductory geology course as a means to discuss the issues of radiometric dating and geologic time.
Description and Teaching Materials
The setup for the activity involves these materials:
- Funnel and Ring Stand
- Medium sized graduated cylinder
- Chopped/Cubed Ice
- Graph Paper for plotting the melting curve
The author's original article has suggestions for a storyline to go along with the activity.
Teaching Notes and Tips
- Large, thin-walled metal funnels are best because of their high thermal conductivity.
- Don't allow too much time between taking the ice out of the freezer and putting it into the apparatus. Some supercooling is desirable.
- Use a large vertical scale on the graphs to produce a steep slope and enable students to easily project the line back to time-zero.
- Start the activity before class begins so that students don't have to deal with the thermal disequilibrium issues at the outset.
- The first couple of data point can be supplied to shorten the activity.
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Assessment
When students have finished plotting their data, they should check their answer for time-zero against the answer provided by the instructor. Student participation is the aim of this exercise.
References and Resources
Wise, 1990 , Using Melting Ice to Teach Radiometric Dating. Journal of Geological Education, 38(1), p. 38-40,69.