Relative dating is the science of determining the relative order of past events (i.e., the age of an object in comparison to another), without necessarily determining their
absolute age, (i.e. estimated age). In geology
rock or
superficial deposits,
fossils and
lithologies can be used to correlate one
stratigraphic column with another. Prior to the discovery of
radiometric dating which provided a means of
absolute dating in the early 20th century,
archaeologists and
geologists used this technique to determine ages of materials. Though relative dating can only determine the
sequential order in which a series of events occurred, not
when they occur, it remains a useful technique especially in materials lacking radioactive isotopes. Relative dating by
biostratigraphy is the preferred method in
paleontology, and is in some respects more accurate (Stanley, 167–69). The
Law of Superposition, which states that older layers will be deeper in a site than more recent layers, was the summary outcome of 'relative dating' as observed in geology from the 17th century to the early 20th century.