Relative age dating superposition
Unlike people, you can’t really guess the age of a rock from looking at it.
Yet, you’ve heard the news: Earth is 4.6 billion years old. That corn cob found in an ancient Native American fire pit is 1,000 years old. Geologic age dating—assigning an age to materials—is an entire discipline of its own.
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 is like saying you are 15 years old and your grandfather is 77 years old.
But the most accurate forms of absolute age dating are radiometric methods. Sedimentary rocks in particular are notoriously radioactive-free zones.
Take students on a neighborhood walk and see what you can observe about age dates around you.Pretty obvious that the dike came after the rocks it cuts through, right?With absolute age dating, you get a real age in actual years.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.If a rock has been partially melted, or otherwise metamorphosed, that causes complications for radiometric (absolute) age dating as well.