Radioactive Decay and Geochronology

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Kirsten Menking

Vassar College

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This activity is part of the On the Cutting Edge Exemplary Teaching Activities collection

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This page first made public: May 3, 2006

Summary

Students create a STELLA model of the radioactive decay process. They then learn how the special radioactive series 238U - 206Pb and 237U - 205Pb can be used to determine both the time when a rock initially crystallized and when it underwent a recrystallization, even when the sample being dated was not a closed system.

Learning Goals

The Radioactive Decay exercise has several purposes:

To convey concepts necessary in modeling a system involving exponential growth and decay
To introduce elementary differential equations
To convey the difference between closed and open systems
To introduce if-then-else logical statements
To convey the importance of secular equilibrium, which allows complex isotopic decay systems to be modeled without taking into consideration radioactive daughters.
To explore concordia-discordia diagrams and how a rock containing two isotopic systems can yield both the age of original crystallization and the time of a later metamorphic event.

Context for Use

This activity was developed for a class introducing dynamical systems modeling to upper level undergraduate students.

Teaching Notes and Tips

Instructor Notes (Acrobat (PDF) 44kB Apr10 06)

Teaching Materials

radioactive_decay_lab-student_version.pdf (Acrobat (PDF) 38kB Jun13 05)
Documented_Isotope_Model.stm ( 25kB Jun13 05)
Documented_UPb_Model.v.1.STM ( 589kB Jun13 05)
Documented_UPb_Model.v.2.stm ( 705kB Jun13 05)
PBLOSS.F90 ( 4kB Jun13 05)
U_series.f90 ( 4kB Jun13 05)
fortran_radioactive_decay.pdf (Acrobat (PDF) 8kB Jun13 05)

Assessment

Radioactive_Decay_Lab-Answer_Key.pdf (Acrobat (PDF) 213kB Jun13 05)
assignment_assessment_2.pdf (Acrobat (PDF) 5kB Jun13 05)

References and Resources

The following are readings for this activity:

Dalrymple, G.B., 1991, The Age of the Earth, Stanford, CA: Stanford University Press, p. 79-90, 99-102, 115-119, and 122-124.
Faure, G., 1986, Principles of Isotope Geology, 2nd Edition, New York: John Wiley and Sons, p. 38-45 and p. 283-296.

Contact the Author

Please contact the author with questions or suggestions.

Controlled Vocabulary Terms

Subject: Geoscience:Geology:Geochemistry:Radioisotopes
Resource Type: Activities:Lab Activity, Computer Applications
Special Interest: Quantitative, Data, models, or simulations:Data, Computer-Based, Data, models, or simulations:Models
Grade Level: College Upper (15-16)
Quantitative Skills: Models and Modeling
Ready for Use: Ready to Use
Topics: Time/Earth History, Solid Earth:Geochemistry:Radioisotopes
Theme: Teach the Earth:Course Topics:Geochemistry

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