What is the difference between radiological and relative dating
Pretty obvious that the dike came after the rocks it cuts through, right?
With absolute age dating, you get a real age in actual years.
It’s based either on fossils which are recognized to represent a particular interval of time, or on radioactive decay of specific isotopes. Based on the Rule of Superposition, certain organisms clearly lived before others, during certain geologic times.
After all, a dinosaur wouldn’t be caught dead next to a trilobite.
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.
For example, which is older, the bricks in a building or the building itself?
You might have noticed that many of the oldest age dates come from a mineral called zircon.
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.
The narrower a range of time that an animal lived, the better it is as an index of a specific time.
No bones about it, fossils are important age markers.