In the lab, I used the law of superposition, the principle of cross-cutting relationships, and index fossils to determine the relative ages of rock layers. Then, I used a mass spectrometer to find the age and identity of an unknown fossil. I learned that radioactive decay can help scientists figure out the age of rocks and minerals. I also learned that dating rock layers and the geologic time scale can help us understand Earth’s history by identifying what was happening to Earth and what lived o
A
Relative dating uses the law of superposition, the principle of cross-cutting relationships, and index fossils to determine the relative ages of rock layers.B
Absolute dating uses tools like a mass spectrometer and natural phenomenon like radioactive decay to determine the ages of rock layers.C
Information from rock layers give clues about what was happening on Earth and what organisms lived at the time the rock layers were formed.