Relative and absolute dating of geologic events
Relative age dating also means paying attention to crosscutting relationships.
No bones about it, fossils are important age markers.Here is an easy-to understand analogy for your students: relative age dating is like saying that your grandfather is older than you.Absolute age dating is like saying you are 15 years old and your grandfather is 77 years old.Look for “absolute” ages such as cornerstones, dates carved into fresh concrete, or dates stamped on manhole covers.Absolute age dating: Have students work alone or in pairs to find an article or paper that uses radiometric age 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.
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.
Applying the principles of relative dating to these rock exposures (also called "outcrops"), we can reconstruct the sequence of events that created the geologic features which we see.
Events can be the deposition of a sedimentary layer, the eruption of a lava flow, the intrusion of magma to form a batholith, a fault (break) in the rock that shifts one side relative to the other side (and causes an earthquake), a fold that bends and distorts rock layers, or any number of other geologic processes.
That’s because zircon is super tough – it resists weathering. Each radioactive isotope works best for particular applications.