Download PART 1: DETERMINING RELATIVE AGE OF ROCKS Think about

 PART 1: DETERMINING RELATIVE AGE OF ROCKS Think about what you learned about relative dating in previous lessons. After students have decided how to establish the relative age of each rock unit, they should list them under the block, from most recent at the top of the list to oldest at the bottom. 1. Describe the Principle of Superposition: 2. Describe the Principle of Crosscutting: 3. Using the diagram on the next page list each of the rock layers from oldest to youngest. 4. Identify each of the following rock layers as igneous, metamorphic, or sedimentary. a. Shale b. Limestone c. Basalt d. Sandstone e. Pegamite f. Slate g. Granite PART 3: PUTTING DATES ON ROCKS AND FOSSILS To answer the next series of questions you need to know that:
• the ratio of U-235 to Pb-207 in the pegmatite is 1:1 (50% uranium, 50% lead)
• the ratio of U-235 to Pb-207 in the granite is 1:3.
• the ratio of U-235 to Pb-207 in the the volcanic ash in the siltstone has a ratio
of U-235:Pb-207 of 47:3 (94% of the original U-235 remains)
• the ratio in the basalt is 7:3 (70% of the original U-235 remains.)
Using the same reasoning about proportions as in radiometric dating lab to determine the
ages of each rock layer. Remember the half life of Uranium 235 is 704 million years.
Figure 4 may help you
5. Give the radiometric dates (or ages for the following rock layers):
a. The age of the pegamite is ____________________________
b. The age of the granite is ______________________________
c. The age of the volcanic ash in the siltstone is _______________________
d. The age of the basalt is ________________________________
6. List the three fossil specimens in relative order (from oldest to youngest) and
identify their radiometric dates or date ranges. Hint: A fossil that is found in
datable rock is assumed to be the same age as the rock. A fossil that is found
between two layers or datable rock is given a date range between the ages of
those two rocks.
a. Youngest fossil ___________________ date(s) ________________
b. Middle fossil ___________________ date(s) ________________
c. Oldest fossil ___________________ dates(s) ________________