Dating rock layers worksheet
To determine the relative age of different rocks, geologists start with the assumption that unless something has happened, in a sequence of sedimentary rock layers, the newer rock layers will be on top of older ones. This rule is common sense, but it serves as a powerful reference point.Geologists draw on it and other basic principles ( to determine the relative ages of rocks or features such as faults.Changes in the environment cause changes in the rocks. Sometimes, the layers are twisted or tilted because of the movement of the Earth’s tectonic plates. Scientists study these layers to learn more about the Earth’s history.For example, a volcanic eruption may create a layer made of hardened ash. Radiometric dating measures radioactive elements in the rocks.Relative age dating also means paying attention to crosscutting relationships.
If you look at a cliff made from sedimentary rock, you’ll notice distinct layers that may even be different colors.I also like this simple exercise, a spin-off from an activity described on the USGS site above.