The teacher should tell the students that there are two basic principles used by geologists to determine the sequence of ages of rocks. Since then, geologists have made many tens of thousands of radiometric age determinations, and they have refined the earlier estimates. This represents Uranium, which emits a series of particles from the nucleus as it decays to Lead Pb- Each of these unstable isotopes has its own characteristic half life. Each time unit was characterized by particular fossils. Objectives of this activity are:
Older fossils cannot be dated by carbon methods and require radiometric dating.
Accuracy of Fossils and Dating Methods
Each team is given a piece of paper marked TIME, on which is written either 2, 4, 6, 8, or 10 minutes. Relative dating is done by observing fossils, as described above, and recording which fossil is younger, which is older. Michael Benton has written over 30 books on dinosaurs and paleobiology. Any geologic feature is younger than anything else that it cuts across. Based on cross-cutting relationships, it was established that the pegmatite is younger than the slate and that the slate is younger than the granite. The Mapping of Geological Structures.