ISP 120

Group Activity 12: Radioisotope Dating

Week 6

All group activities must include a statement signed by all members of your group that each group member fully participated in the activity. To start you should open a new Word document entitled something like "Group Activity 11" and put the names of your group members at the top. Save it to the desktop and save frequently during the hour.

Learning Goals for this Activity

  1. You will understand the basic scientific concepts that underlay radioisotope dating.
  2. You will learn about the essential characteristics of exponential decay.
  3. You will be able to estimate the age of artifacts given the amount of a certain radioisotope with a known half life.
1. (Age of moon)

a.  Rock samples brought back from the moon by Apollo astronauts have approximately 58% of the original amount of Uranium 238 present. Using the fact that Uranium decays at a rate of approximately 7.41% every 500 million years, approximate how old the rocks are.  (Hint.  One way to approach this is to make a table in Excel that looks like

Years After Formation % Uranium 238 present
0 100
500 92.59
1000 ......

Continue the table until the percentage of Uranium 238 is about 58%.)

b. The rocks give an estimate for the age of the moon. What other issues would you need to take into consideration in using this method to date the age of the moon?

 apollo17_schmitt_boulder.jpg (36001 bytes)
2. Some of the most famous Cro-Magnon cave paintings are located in Lascaux, France. On the right is an image from Lascaux. Charcoal found in the cave has approximately 14% of the carbon 14 found in living wood. Estimate the age of the paintings. (Carbon 14 decays approximately 1.202% every 100 years.)