The video segment comes with follow-up discussion questions and printable essays for the classroom.
With absolute age dating, you get a real age in actual years.
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.
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.
What’s more, if the whole rock is badly weathered, it will be hard to find an intact mineral grain containing radioactive isotopes.
Related teaching materials and games are also linked on the website.
Montana's Office of Public Education offers a lesson plan which teaches students about radiometric dating using information provided online about American Indian bison bones and prehistoric kill sites.The activity calls for students to simulate half-life properties of isotopes using bags of beads as "rocks and fossils." Appropriate for grades 5 to 8, the activity assigns parent isotopes to different color beads and asks students to solve problems such as arranging the "fossils" in age from youngest to oldest and finding the two "fossils" which are closest in age.The college also offers a game that simulates radioactive decay using dice.Absolute age dating is like saying you are 15 years old and your grandfather is 77 years old.To 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. This rule is common sense, but it serves as a powerful reference point.The plan guides students through the radiometric analysis of prehistoric evidence, radiometric terminology and half-lives of carbon 14.