Question

determine whether the method listed is an absolute or relative dating method
law of superposition
uranium-lead dating
speciation
fossilization

Explanation:

• Law of Superposition: This is a principle in geology. It states that in undisturbed sedimentary rock layers, the oldest layers are at the bottom and the younger layers are on top. It is used to determine the relative order of rock layers and fossils within them. So, it is a relative dating method.
• Uranium - Lead Dating: This is a radiometric dating method. It is based on the radioactive decay of uranium isotopes (\(^{238}U\) and \(^{235}U\)) into lead isotopes (\(^{206}Pb\) and \(^{207}Pb\)). By measuring the ratio of parent (uranium) to daughter (lead) isotopes in a sample, an absolute age (in years) of the sample (such as a rock or mineral) can be calculated. So, it is an absolute dating method.
• Speciation: Speciation is the process by which new species arise. In the context of dating, when we use the appearance or disappearance of a species in the fossil record to determine the age of a rock layer relative to other layers (e.g., if a certain species is only found in a particular set of layers, we can say that those layers are older or younger than layers with different species assemblages), it is a relative dating method.
• Fossilization: While fossilization is the process of forming fossils, when we use fossils (e.g., index fossils - fossils of organisms that were widespread but existed for a short geological time) to compare the ages of rock layers (if two rock layers have the same index fossil, they are likely to be of similar relative age), it is a relative dating method.

Answer:

• Law of Superposition: Relative
• Uranium - Lead Dating: Absolute
• Speciation: Relative
• Fossilization: Relative