Tree Ring Cross-Dating Exercise

1. Go to the web page http://tree.ltrr.arizona.edu/skeletonplot/introcrossdate.htm

2. Read the instruction pages.

3. Try counting the rings on the conifer tree ring sample where every tenth ring is marked to see if our count agrees with theirs.

4. Notice how to detect locally absent and false rings.

5. Try cross dating by using skeleton plotting.

1) Begin with 11 rings

2) Set the Sensitivity at 2

3) Set the Absolute Value at 2

4) Leave the rest of the settings at their default values.

5) Click on Restart a New Core

6) For every small tree ring make a mark on the graph. Smaller rings have taller marks. If a sample has fewer than two small rings it may be too difficult to date. Click on Restart a New Core to see a new sample.

7) When you have finished marking your graph, click on Master to see the master chart.

8) With the mouse pointed to the top section of your graph, slide your graph along the master to find the dates that match. For a better match you may want to change the height of all the marks on the master by changing the Abs Value setting.

9) Write your answer for the dating period from the master chart numbers. e.g. 1971 to 1981.

10) Click on Answer to check your answer.

11) Practice makes perfect. Be sure you practice enough to acquire speed and accuracy so you can date real tree rings at the next class.