Using relative dating principles
Relative dating does not provide actual numerical dates for the rocks.Fossils are important for working out the relative ages of sedimentary rocks.Throughout the history of life, different organisms have appeared, flourished and become extinct.Many of these organisms have left their remains as fossils in sedimentary rocks.Free 5-day trial Discover how geologists study the layers in sedimentary rock to establish relative age.Learn how inclusions and unconformities can tell us stories about the geologic past.Relative dating is used to arrange geological events, and the rocks they leave behind, in a sequence.
The regular order of occurrence of fossils in rock layers was discovered around 1800 by William Smith.
In a way this field, called geochronology, is some of the purest detective work earth scientists do.
There are two basic approaches: relative age dating, and absolute age dating.
To determine the relative age of different rocks, geologists start with the assumption that unless something has happened, in a sequence of sedimentary rock layers, the newer rock layers will be on top of older ones. This rule is common sense, but it serves as a powerful reference point.
Geologists draw on it and other basic principles ( to determine the relative ages of rocks or features such as faults.