Absolute Dating
This page authored by Emily Pope and Jonathan Payne, Stanford University. Portions of this activity
are based on an original activity by Anne Egger, Stanford University.
Summary
The purpose of this activity is introduce students to the mathematical principles behind radiometric age dating, and to evaluate some applications of absolute dating to geologic problems. In the first part of this activity, students perform an experiment in which they use dice as a proxy for radioactive isotopes, and calculate the rate of decay of their dice collection. Once students have established and modeled the principles of isotope half-lives, they are introduced to actual decay schemes used in geochronology, and use these schemes to answer several questions relating to actual and hypothetical geological problems.
Learning Goals
Upon completion of this exercise students will be able to:
1. Model the statistics used to date rocks with the decay of radioactive isotopes.
2. Distinguish which decay schemes are most effective for dating different kinds of materials.
3. Correlate relative time boundaries established by the fossil record with absolute dates.
1. Model the statistics used to date rocks with the decay of radioactive isotopes.
2. Distinguish which decay schemes are most effective for dating different kinds of materials.
3. Correlate relative time boundaries established by the fossil record with absolute dates.
Context for Use
This activity is designed for an Introduction to Earth History course that uses the extinction of
dinosaurs as a case-study to study major concepts relating to Earth History. However, it is
applicable as an absolute dating project for any introductory Earth History or Earth Science
course.
Before starting this activity, students should have at least a good understanding of relative age dating, and preferably have completed Principles of Biostratigraphy. As this lab is designed for students to work in small groups, it can be used for a large range of class sizes. However, classes are limited in size by the number of dice it is appropriate to have in one classroom, but should be large enough that several groups can collect data which can then be compiled by the whole class.
The first part of this activity (1. and 2.) can be completed in one 1-2 hour class period, the second portion (3.) can be assigned as homework.
Before starting this activity, students should have at least a good understanding of relative age dating, and preferably have completed Principles of Biostratigraphy. As this lab is designed for students to work in small groups, it can be used for a large range of class sizes. However, classes are limited in size by the number of dice it is appropriate to have in one classroom, but should be large enough that several groups can collect data which can then be compiled by the whole class.
The first part of this activity (1. and 2.) can be completed in one 1-2 hour class period, the second portion (3.) can be assigned as homework.
Teaching Materials
Assignment handout: Absolute Dating (Microsoft Word 1MB Feb4 08)
The assignment hand-out explains the problems students must solve, and asks students to answer questions as they progress through the activity.
Additional materials needed: paper, pencil, graph paper, straight edge, and one bucket and about 40-100 dice per group of students.
The assignment hand-out explains the problems students must solve, and asks students to answer questions as they progress through the activity.
Additional materials needed: paper, pencil, graph paper, straight edge, and one bucket and about 40-100 dice per group of students.
Teaching Notes and Tips
Assessment
References and Resources
The following references from the primary literature were used in developing this activity:
- Characteristics of Early Cambrian Fauna from eastern San Bernardino County, California by Jack D. Mount, from Southern California Paleontological Society Special Publications, no. 2, 1980, pp. 19-29
- Swisher et al., 1992, Coeval 40Ar/39Ar Ages of 65.0 Million Years Ago from Chicxulub Crater Melt Rock and Cretaceous-Tertiary Boundary Tektites. Science, 257:954-958.
- Izett et al., 1991, 40Ar/39Ar Age of Cretaceous-Tertiary Boundary Tektites from Haiti. Science, 252:1539-1542.
- Palamarczuk et al., 2002. The Cretaceous/Paleogene boundary in Argentina: New evidence from dinoflagellate, foraminiferal, and radiometric dating. GSA Abstracts with Programs, 34:137.
- Courtillot et al., 2000, Cosmic markers, 40Ar/39Ar dating and paleomagnetism of the KT sections in the Anjar Area of the Deccan large igneous province. Earth and Planetary Science Letters, 182:137-156.
- Pillmore and Miggins, 2000, New 40Ar/39Ar age determinations on the K/T boundary interval; possible constraints on the timing of the K/T event? GSA Abstracts with Programs, 32:452.
- Krogh et al., 1993, Fingerprinting the K/T impact site and determining the time of impact by U-Pb dating of single shocked zircons from distal ejecta. Earth and Planetary Science Letters, 119:425-429.
- Exercise 2:Relative and absolute dating of geologic events by John R. Groves at the University of Northern Iowa
