Section Warm-Up
Just as you know how old you are by the regularly occurring and predictable passing of each year in time, we can know how old Earth materials are by the regular and predictable changes that take place to their internal atomic compositions with time. For example, certain carbon atoms that become incorporated in the bodies of living things change predictably over time after the organism dies.
You are probably familiar with the concept of carbon-14 dating, which is based on this fact and is a method used to assign absolute ages to very old materials found from the past. Specifically, those carbon atoms undergo chemical changes to become nitrogen atoms, and they do so at a known constant rate. By studying the ratio of carbon to nitrogen atoms in a sample, you can use the rate of change to calculate how many years ago the "clock" of change started ticking (or how many years ago the organism died and its carbon atoms started changing to nitrogen atoms). Click the tab below to complete the warm-up activity.
Warm-up Activity
Number of Years Elapsed Since Organism Died |
Percentage of Original Carbon-14 Left in the Organism’s Remains |
0 |
100 |
5,730 |
50 |
11,460 |
25 |
17,190 |
12.5 |
22,920 |
6.25 |
This table shows some data taken from a carbon-14 study. Use the whiteboard on the next tab and the data in the table to draw a graph showing how much of the original carbon is left after each period of time. Place a dot on the appropriate place on the graph for each time period, and then draw a line to connect all the dots. The first dot is drawn in for you. Save your file. You will refer to it later in this section and will learn more about how carbon-14 dating works.
