Discovery of radioactive dating
Like the other kind of dating, geologic dating isn’t always simple.
Activity: Further discussion: Good overview as relates to the Grand Canyon: age dating: Use with this cross section of the Grand Canyon from the USGS’s teaching page: Canyon Have students reconstruct a simple geologic history — which are the oldest rocks shown? Are there any that you can’t tell using the Rule of Superposition?
What’s more, if the whole rock is badly weathered, it will be hard to find an intact mineral grain containing radioactive isotopes.
You might have noticed that many of the oldest age dates come from a mineral called zircon.
Pretty obvious that the dike came after the rocks it cuts through, right?
Absolute age dating: Have students work alone or in pairs to find an article or paper that uses radiometric age dating.
For example, which is older, the bricks in a building or the building itself?