GeoTime

Geotime is the way that scientists look at the history of the Earth. It's like putting a timeline on the earth, so that scientists can figure out when different kinds of rocks were formed, when volcanoes and mountains were formed, and when different kinds of plants and animals arrived. For example, geologists might be able to tell that a certain type of rock formed around 250 million years ago because they can look at maps of the Earth from that time to see what kinds of rocks were around.