Chart of a few different isotope half lifes: In reality, geologists tend to mix and match relative and absolute age dates to piece together a geologic history.
If a rock has been partially melted, or otherwise metamorphosed, that causes complications for radiometric (absolute) age dating as well.
Abstract The complex geologic development of the Sigsbee Escarpment in the Southern Green Canyon area has been studied in great det ail using a comprehensive suite of geophysical and geotechnical data.
Integration of these data led to the recognition of certain geologic indicators that assist, either directly, or indirectly, in "filling the gaps" in the geologic history of the Atlantis area.
Here is an easy-to understand analogy for your students: relative age dating is like saying that your grandfather is older than you.