In geology, the age of rock layers can be determined through a principle known as the Law of Superposition. This principle states that in any undisturbed sequence of rock layers, the youngest rocks are found at the top and the oldest rocks are found at the bottom. Geologists also use techniques such as radiometric dating to more accurately determine the absolute age of rock layers. Radiometric dating relies on the decay of radioactive isotopes within the rocks to calculate how long ago the rocks formed. This method allows geologists to assign numerical ages to rock layers and establish a timeline of Earth's history. In addition to relative and absolute dating methods, geologists also examine the fossil record within rock layers to further refine the age interpretation. By identifying index fossils that are known to have existed during specific time periods, geologists can correlate rock layers from different locations and establish a more detailed chronology of Earth's geological history. Overall, the interpretation of the age of rock layers is a complex process that involves a combination of principles and techniques in order to piece together the puzzle of Earth's past.