Minnesota DNR-Lands and Minerals Division. Geology is the study of the history of the earth, which includes its rocks and fossils. Geologists study this history to find out how the earth looked in the past and how it has changed.
Geologists are earth detectives.
They piece together small bits of information to create the story of the earth. Geologists try to understand how rocks were created and destroyed. The events which shaped the earth are put in order, from oldest to youngest, to understand how the earth changed over time. Geologists break time down into geologic time units called eras . Each era contains smaller time units called periods .