PLAYING THE DATING GAME IN LAB: RELATIVE AND ABSOLUTE AGE DATING IN AN EARTH AND SPACE SCIENCE LAB DESIGNED FOR PRE-SERVICE ELEMENTARY TEACHERS

Geology/Astronomy 106L is a two-hour Earth and space science lab that fulfills part of the science content requirement of elementary education majors at Iowa State University. Taught each semester by graduate teaching assistants in geology, the lab enrolls ~85 students divided into four sections. It complements a two-credit online course taught by two science faculty.

Given the significant amount of content to be covered to fulfill the licensure requirements, most lab sessions cover different topics, with only plate tectonics and rocks and minerals extending over two lab periods. Geologic time is one of the most fundamental concepts to be learned in such a course, but also one of the most challenging for students to understand. The learning objectives for this lab period are: 1. to learn the principles that are used to put events and rocks in a relative sequence, 2. to place in a relative age sequence a series of events and fossil and rock specimens, 3. To use a timeline to place significant events in Earth history, and 4. To apply the concept of half-life to dating rocks and minerals.

We have assembled a series of short exercises that engage the students in activities that address the learning objectives. These include:

1. Applying the principles of relative dating to block diagrams of geologic formations/events created by the students;
2. Using the geologic timescale to determine the age/age-range of fossils from different periods;
3. Flipping pennies to simulate the process of radioactive decay (heads up = parent isotope, tails up = daughter isotope);
4. Calculating the age of rocks or fossils, given the ratio of parent-daughter material and the known half-life of various isotopic systems;
5. Using a Geiger counter to measure radioactivity in selected household objects.

Students like breaking down complicated concepts like half life into more easily understood scenarios and to use the Geiger counter to be able to ‘see’ the radiation of common household objects.