How do Scientist Figure Dates on Fossils?


1) How do fossils form? List at least 2 ways.

2) Why will the fossil record always be an incomplete record of life's history?

3) What is relative dating? Describe how it is done.

4) What are index fossils?

5) What is radioactive dating? How is it done?

Half-life activity (Please do this activity with a partner across from you at your lab table):

1) Place an X in the middle of each of the 100 squares in the 10 x 10 table below.
2) Cut each one of the squares and randomly place them in a plastic cup.
3) Shake the cup up with your hand on top to mix up the squares inside.
4) Spill them onto your lab table with your partner. Squares that overlap need to be separated and spread out so that they do not cover others.
5) Remove all squares with an X showing and put them back into the cup. Count the number of squares you return to the cup and enter that number in the data table.
6) Repeat step 3, 4, & 5 until you run out of squares.
7) Plot a line graph of your data

Data Table
Graph of Results
# of squares returned to the cup


6) How many spills were required to remove half the squares in the cup?

7) How many spills were required to remove 3/4 of the squares from the cup?

8) How many spills did it take to not have any more squares?

9) If each spill represents on year, what is the half-life of the squares?

10) What amount of time would "one spill" represent if the squares were carbon-14?

11) If you multiply the half-life of carbon 14 by the number of spills that it took for you to not have any more squares, what do you get?

12) What is the oldest age of fossils that carbon 14 can date accurately? Explain what you think might be the reason for this.

13) Please complete the following table with your instructors help.

isotope method
What kind of fossils/materialscan be dated with this method
carbon 14-12
potassium 40 - argon
uranium - lead

100 squares for "X"ing and cutting