You may not associate geology with time, but the former greatly depends on the latter.In this lesson we'll discuss both absolute and relative time, and how they work together to give us a detailed history of Earth.Geologists establish the age of rocks in two ways: numerical dating and relative dating.Numerical dating determines the actual ages of rocks through the study of radioactive decay.

This term means that older artefacts are usually found below younger items.

Relative dating cannot establish absolute age, but it can establish whether one rock is older or younger than another.

Relative dating requires an extensive knowledge of stratigraphic succession, a fancy term for the way rock strata are built up and changed by geologic processes.

For example, 60 million years is a measure of absolute time. These are numerical representations of time, and they give us specific points of reference.

We have a long record of events in absolute time but much of that occurred before humans were on Earth to write it down.