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Date a Rock
This lesson shows students that age-dating rocks involves counting atoms and comparing the counts. Students use simulated rock samples, which show a highly magnified selection of 128 atoms, each sample with a different proportion of the atoms of two different elements: a parent radioisotope, and its daughter product. By counting the parent radioactive atoms and knowing the half-life of those atoms, students can figure the number of half-lives since the sample solidified, and therefore the age of the sample.
Intended for grade levels:
  • Middle (6-8)
  • High (9-12)
Type of resource:
  • For the classroom:
    • Lesson plan
Subject:
  • Geological Sciences:
    • Geologic time
Technical requirements:
No specific technical requirements, just a browser required
Cost / Copyright:
No cost
Copyright 2003 ENSI (Evolution and the Nature of Science Institutes). This material may be copied only for noncommercial classroom teaching purposes, and only if this source is clearly cited.
DLESE Catalog ID: DLESE-000-000-004-783
Educational standards:
  • National Science Education Standards (NSES):
    • 5-8:
      • Unifying concepts and processes:
        • Change, constancy, and measurement
        • Evidence, models, and explanation
        • Systems, order, and organization
      • B - Physical science:
        • Properties and changes of properties in matter
      • D - Earth and space science:
        • Earth's history
    • 9-12:
      • Unifying concepts and processes:
        • Change, constancy, and measurement
        • Evidence, models, and explanation
        • Systems, order, and organization
      • B - Physical science:
        • Structure and properties of matter
        • Structure of atoms
Resource contact / Creator / Publisher:
Publisher: Evolution and the Nature of Science Institutes


Author: Karen Kalumuck
San Francisco Exploratorium, Biology Education Director