Radiometric age dating activity


The discovery of radioactivity and its application to dating rocks is perhaps one of the greatest scientific achievements affecting the Earth Sciences.With the discovery of radioactive isotopes more then one hundred years ago, scientists quickly realized that the radioactive decay of materials found in rocks could be used to date the rocks and consequently change the "relative" geologic time scale into an "absolute" time scale.It’s based either on fossils which are recognized to represent a particular interval of time, or on radioactive decay of specific isotopes. Based on the Rule of Superposition, certain organisms clearly lived before others, during certain geologic times.After all, a dinosaur wouldn’t be caught dead next to a trilobite.This site stores nothing other than an automatically generated session ID in the cookie; no other information is captured.In general, only the information that you provide, or the choices you make while visiting a web site, can be stored in a cookie.Relative age dating also means paying attention to crosscutting relationships.



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.