Using Melting Ice to Teach Radiometric Dating

Developed by Donald Wise, Franklin and Marshall College. Taken from Wise, 1990 .

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.

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.

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.

Quantiative Skills Addressed

Interpretation of graphical information, Estimation

Geoscience Topics Covered

Time/Earth History