Absolute and relative rock dating
For example, which is older, the bricks in a building or the building itself?
Are there repairs or cracks in the sidewalk that came after the sidewalk was built?
Unlike people, you can’t really guess the age of a rock from looking at it.
Take students on a neighborhood walk and see what you can observe about age dates around you.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.Like the other kind of dating, geologic dating isn’t always simple.Activity: Further discussion: Good overview as relates to the Grand Canyon: age dating: Use with this cross section of the Grand Canyon from the USGS’s teaching page: Canyon Have students reconstruct a simple geologic history — which are the oldest rocks shown? Are there any that you can’t tell using the Rule of Superposition?