Which evidence would confirm that a given rock layer is newer than the layers around it
There are several types of evidence that can be used to confirm that a given rock layer is newer than the layers around it. These include:
1. Law of Superposition: This principle states that in an undisturbed sequence of rock layers, the youngest rocks are at the top, while the oldest rocks are at the bottom. If a rock layer is found to be higher in the sequence than the surrounding layers, it is likely to be younger.
2. Fossil Dating: Fossils can serve as useful markers for relative dating. By comparing the fossils found in different rock layers, scientists can determine the relative age of the layers. If a fossil species is found in a higher rock layer but not in the layers below, it suggests that the higher layer is younger.
3. Cross-cutting relationships: If a rock layer is found to cut across another existing rock layer, it is younger than the layer it cuts through. For example, if a fault cuts through a pre-existing layer, the fault is younger than that layer.
4. Index fossils: Index fossils are specific fossils that lived for a short period of time and had a wide geographic distribution. By finding index fossils in different rock layers, scientists can correlate the ages of those layers in different locations. If an index fossil is found in a higher layer but not in the lower layers, it indicates that the higher layer is younger.
5. Radiometric Dating: Radiometric dating techniques, such as the decay of radioactive isotopes, can provide absolute ages for rocks. If radiometric dating is conducted on the layers and indicates that the rock layer in question is younger than the ones surrounding it, it confirms its relative age.
It is important to note that positive evidence from several of these methods will generally provide stronger confirmation of the relative age of a given rock layer.