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.How much of your life do you spend thinking about time? Time comes in different forms in geology, mainly absolute and relative.They are both important in terms of Earth's history and its geological timeline, and they work together in concert to build the planet's geological record.These artifacts can be placed in order, but requires external information to determine which end of the series is younger or older.
We have a long record of events in absolute time but much of that occurred before humans were on Earth to write it down.
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.
According to the laws of superposition, a strategic layer that is higher has been deposited more recently.
The oldest strata are at the bottom of the sequence.