To establish the age of a rock or a fossil, researchers use some type of clock to determine the date it was formed. Geologists commonly use radiometric dating methods, based on the natural radioactive decay of certain elements such as potassium and carbon, as reliable clocks to date ancient events.

What are two ways to date rocks?

​There are two main ways to determine the age of a rock, these are Relative dating and Absolute dating. Relative dating is used to determine the relative order of past events by comparing the age of one object to another.

What is the youngest rock layer?

The law of superposition states that rock strata (layers) farthest from the ground surface are the oldest (formed first) and rock strata (layers) closest to the ground surface are the youngest (formed most recently). A fossil is the remains or traces of plants and animals that lived long ago.