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Ages of Rocks and the Earth

Kéyah Math Project development team: Nancy Zumoff, Christopher Schaufele, Steven Semken, Tracy Perkins, Lynn Onken, Philippe Laval, David Gonzales, and Andrew Becenti (deceased).
Kéyah Math Project directed by Steven Semken, Arizona State University; and Christopher Schaufele and Nancy Zumoff, Professors of Mathematics, Emeritus.
Archived at Arizona State University School of Earth and Space Exploration.

Summary

This activity introduces students to the mathematics of radiometric dating. Students first apply the rubidium-strontium isotopic system to date rock samples from the San Juan Mountains of southwest Colorado, and then to date a meteorite and estimate the absolute age of the Earth.

Click here to view the full activity on the Kéyah Math Project website.

Learning Goals


Objectives
  • Review the use of radioactive decay as a "natural clock" for dating rocks.
  • Apply the decay equation for the rubidium-strontium isotope system to obtain ages for rock samples from the San Juan Mountains in southwest Colorado.
  • Apply this equation to data from a meteorite to estimate the age of the Earth.

    Mathematical Skills
  • Use basic algebra.
  • Solve exponential equations.
  • Use logarithms.
  • Context for Use

    This activity consists of a set of quantitative problem-solving exercises that can be used as an in-class activity or an assignment in any introductory geology, geography, Earth science, or Earth materials course.

    Description and Teaching Materials

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    Teaching Notes and Tips

    An Instructor's Guide to all Kéyah Math activities is available online from the Instructor Resources page on the Kéyah Math website.

    Assessment

    Students record their work and answers in a word-processor document or a notebook, which can be submitted to the instructor for assessment. Solutions to these problems are available online from the Instructor Resources page on the Kéyah Math website.

    References and Resources

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