Radiometric age dating activity
Read the pages listed below, which are available online through Library Reserves.But the most accurate forms of absolute age dating are radiometric methods. Sedimentary rocks in particular are notoriously radioactive-free zones.This method works because some unstable (radioactive) isotopes of some elements decay at a known rate into daughter products. Half-life simply means the amount of time it takes for half of a remaining particular isotope to decay to a daughter product. Good discussion from the US Geological Survey: geochronolgists just measure the ratio of the remaining parent atom to the amount of daughter and voila, they know how long the molecule has been hanging out decaying. So to date those, geologists look for layers like volcanic ash that might be sandwiched between the sedimentary layers, and that tend to have radioactive elements.In this activity, you will be able to combine your knowledge of relative dating methods (learned in Activity 7) with the absolute dating method to determine more accurately the geologic history of a region.
These schematic columnar sections contain the stratigraphic sequence for the Transvaal Basin in Africa and the Nabberu Basin and Hamersley Basin in Western Australia.
Here is an easy-to understand analogy for your students: relative age dating is like saying that your grandfather is older than you.