Often when geologists examine rock outcrops like the one illustrated above they are interested in not only the types of rocks present, but the order in which they formed.
When they put events in chronological order like they use Relative Dating.
Relative age dating also means paying attention to crosscutting relationships.
Say for example that a volcanic dike, or a fault, cuts across several sedimentary layers, or maybe through another volcanic rock type.
What’s more, if the whole rock is badly weathered, it will be hard to find an intact mineral grain containing radioactive isotopes.
You might have noticed that many of the oldest age dates come from a mineral called zircon.
For example, lets put the following movies in order of relative age from oldest to youngest: Twilight, Finding Nemo, the Avengers, the Hunger Games.I also like this simple exercise, a spin-off from an activity described on the USGS site above.Take students on a neighborhood walk and see what you can observe about age dates around you.We don't need to know what year any of these movies came out to place them in order of relative age.Nemo is the oldest, followed by Twilight, Hunger Games, and the Avengers Again, we have not stated anything about the actual age of these movies, we've just put them in order relative to one another.