The diagram on the right shows how the original, horizontal rock layers have changed due to tectonic activity. Relative dating puts the sequences of rocks layers into chronological order. Although the layers are no longer horizontal, geologists are able to determine their order.

What does the relative date of a rock tell you?

Relative dating puts geologic events in chronological order without requiring that a specific numerical age be assigned to each event. Second, it is possible to determine the numerical age for fossils or earth materials.

What does the relative age of a rock layer describe?

The relative age of a rock is its age in comparison with other rocks. The intrusion (D) cuts through the three sedimentary rock layers, so it must be younger than those layers. The principle of superposition states that the oldest sedimentary rock units are at the bottom, and the youngest are at the top.