Quantitative Skills > Teaching Resources > Activities > Understanding Radioactivity in Geology: The Basics of Decay

Understanding Radioactivity in Geology: The Basics of Decay

Christina Stringer—University of South Florida, Tampa FL 33620
This activity was developed for Spreadsheets Across the Curriculum ( This site may be offline. ) . National Science Foundation, DUE 0442629.

This activity was selected for the On the Cutting Edge Exemplary Teaching Collection

Resources in this top level collection a) must have scored Exemplary or Very Good in all five review categories, and must also rate as “Exemplary” in at least three of the five categories. The five categories included in the peer review process are

  • Scientific Accuracy
  • Alignment of Learning Goals, Activities, and Assessments
  • Pedagogic Effectiveness
  • Robustness (usability and dependability of all components)
  • Completeness of the ActivitySheet web page

For more information about the peer review process itself, please see http://serc.carleton.edu/NAGTWorkshops/review.html.

This activity has benefited from a review and suggestion process as a part of an activity development workshop.

This activity has benefited from input from faculty educators beyond the author through a review and suggestion process as a part of an activity development workshop. Workshop participants were provided with a set of criteria against which they evaluated each others' activities. After the review, the authors developed a plan for revising their activities based on the feedback they received from their peers. To learn more about this review process, see http://serc.carleton.edu/quantskills/review_processes.html#2006.

This page first made public: Jul 23, 2006


One of a collection of PowerPoint/Excel modules designed to reinforce quantitative skills in geologic context. The module explores the exponential decay of radioactive parents through the analogy with popping popcorn. Students build a spreadsheet to calculate the number of unpopped kernels of popcorn as a function of time starting with the probability that a given kernel will pop during a 10-sec interval. The module introduces the mathematics of the exponential function as a modeling function in both analytical and numerical contexts.

Learning Goals

Students will:
  • Consider a familiar occurrence of exponential decay in a quantitative way.
  • Gain experience in forward modeling of an exponential decay phenomenon.
  • Consider the relationship between the decay constant and the probability that a particular parent atom of a radioactive isotope will convert to its radiogenic daughter atom
  • Gain experience in fitting a trendline to a column of data.

Context for Use

This activity was designed for an upper-division math-in-geology course for geology majors but can easily be used in an introductory undergraduate geoscience class, as well as a high school pre-calculus class.

Description and Teaching Materials

module (PowerPoint 703kB Dec24 06)

Teaching Notes and Tips

The module is intended as a stand-alone resource. It can be used as a lab exercise or handwork assignment, or as the basis of an interactive classroom activity with just-in-time teaching of mathematical problem solving. The problem context and the mathematical content are developed within the module.


The module ends with hand-in questions that the students answer by manipulating the spreadsheets that they prepared while working through the module.

References and Resources