Does radiometric dating tell us past
However, note that because of the "principle of cross-cutting relationships", careful examination of the contact between the cave infill and the surrounding rock will reveal the true relative age relationships, as will the "principle of inclusion" if fragments of the surrounding rock are found within the infill.
Cave deposits also often have distinctive structures of their own (e.g., spelothems like stalactites and stalagmites), so it is not likely that someone could mistake them for a successional sequence of rock units. Each of them is a testable hypothesis about the relationships between rock units and their characteristics.
Using the decays of uranium and thorium, our galaxy has been found to be between 10 and 20 billion years old and the earth has been found to be 4.6 billion years old. Within experimental error, this estimate agrees with the 15 billion year estimate of the age of the Universe.As an example of how they are used, radiometric dates from geologically simple, fossiliferous Cretaceous rocks in western North America are compared to the geological time scale.To get to that point, there is also a historical discussion and description of non-radiometric dating methods.For example, the principle of superposition is based, fundamentally, on gravity.In order for a layer of material to be deposited, something has to be beneath it to support it.
These are often characterised as the norm, rather than the exception.