the older method required two samples for dating and could produce imprecise dates if the argon was not fully extracted. like the other kind of dating, geologic dating isn’t always simple. the best methods for finding the absolute dates of different rock layers. are able to recognise fossils that are characteristic of various rock layers. each volcanic eruption produces a new deposit of ash and rock.
How do we know the ages of fossils and fossil-bearing rocks?
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, you get a real age in actual years. these include radiometric dating of volcanic layers above or below the fossils or by comparisons to similar rocks and fossils of known ages. rocks (made from mud, sand, gravel or fossil shells) and volcanic lava flows are laid down in layers or beds. determine the relative age of different rocks, geologists start with the assumption that unless something has happened, in a sequence of sedimentary rock layers, the newer rock layers will be on top of older ones.