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.Here is an easy-to understand analogy for your students: relative age dating is like saying that your grandfather is older than you.
To determine the ages of these specimens, scientists need an isotope with a very long half-life.
Geologists have studied the order in which fossils appeared and disappeared through time and rocks. Fossils can help to match rocks of the same age, even when you find those rocks a long way apart.
This matching process is called correlation, which has been an important process in constructing geological timescales.
We know the oldest rocks are at the bottom and the youngest are at the top, but we want some actual dates. Drag and drop the rock sample from each layer onto the dating method you think will tell us its age.
You can help us choose the best absolute dating method for each rock. To learn more about the dating methods, select the image from the lab.