Cutting Edge > Rates and Time > Teaching Activities > Dating Students: Relative vs. Numerical Time

Measuring Geologic Time: The Case of Bloody Canyon

Susan Zimmerman
,
Center for AMS, Lawrence Livermore National Lab
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This activity was selected for the On the Cutting Edge Reviewed Teaching Collection

This activity has received positive reviews in a peer review process involving five review categories. The five categories included in the 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 page first made public: Feb 10, 2012

Summary

This activity introduces students to the fundamental ideas of relative versus radiometric dating, using the students themselves as a sample population. In the first half, the students attempt to order the people in the group in a relative sense, using physical observations and their memory-record of historical events. In the second half, the students use increasingly precise estimates of their age (from their birthdays) to check their relative order against their absolute age order. The discussion should include concepts of precision and accuracy, estimation, observation versus inference, and drawing conclusions based on incomplete, inaccurate, or updated information.

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Context

Audience

This exercise will work best with a small group (~20), and is aimed at undergraduates in an introductory course in physical or historical earth science, but may provoke more sophisticated discussions in upper-level courses; a wide-range of student ages is ideal (e.g., community college) but not necessary.

Skills and concepts that students must have mastered

Students should have a some introduction to earth science, including the differences between observations and inferences, concepts of weathering and erosion, and the basics of radiometric dating, but the preliminary presentation and discussions can be tuned to include review or presentation of these concepts.

How the activity is situated in the course

The activity is intended to be a dynamic illustration of the power and pitfalls of measuring geologic time, to get students thinking about how geologists order and date events in earth history, give them a sense of the potential problems, and why dates in earth's history sometimes change.

Goals

Content/concepts goals for this activity

Higher order thinking skills goals for this activity

Other skills goals for this activity

Description of the activity/assignment

In this lab, students are introduced to the difference between relative and absolute dating, using the students themselves as the material to be ordered. Initially, the students are asked to develop physical clues to put themselves in order from youngest to oldest (exposing the inferences we make unconsciously about people's ages), and this will be refined/modified using a list of current events from an appropriate historical period that more and more of the students will remember, depending on their age (among other variables). Absolute age is introduced by having the students order themselves by birth decade, year, month, and day, and comparing the absolute age order to the order worked out in the relative-dating exercise, with a discussion of dating precision and accuracy.

Determining whether students have met the goals


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