Relative dating interactive
No bones about it, fossils are important age markers.But the most accurate forms of absolute age dating are radiometric methods. Sedimentary rocks in particular are notoriously radioactive-free zones.You might have noticed that many of the oldest age dates come from a mineral called zircon.That’s because zircon is super tough – it resists weathering. Each radioactive isotope works best for particular applications.The Keyword(s) and Warm-up are completed during the first five to ten minutes of class.Each student should have a planner with a daily record of the topic covered and classwork.There are two basic approaches: relative age dating, and absolute age dating.Here is an easy-to understand analogy for your students: relative age dating is like saying that your grandfather is older than you.
What’s more, if the whole rock is badly weathered, it will be hard to find an intact mineral grain containing radioactive isotopes.The half-life of carbon 14, for example, is 5,730 years.On the other hand, the half-life of the isotope potassium 40 as it decays to argon is 1.26 billion years.So carbon 14 is used to date materials that aren’t that old geologically, say in the tens of thousands of years, while potassium-argon dating can be used to determine the ages of much older materials, in the millions and billions year range.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.Take students on a neighborhood walk and see what you can observe about age dates around you.For example, which is older, the bricks in a building or the building itself?Geologists draw on it and other basic principles ( to determine the relative ages of rocks or features such as faults.Relative age dating also means paying attention to crosscutting relationships.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.