Principles of relative dating in geology
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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.
The narrower a range of time that an animal lived, the better it is as an index of a specific time.
No bones about it, fossils are important age markers.
Students can watch the lessons on their own schedule and transfer their credit recommendations to thousands of colleges and universities.Look for “absolute” ages such as cornerstones, dates carved into fresh concrete, or dates stamped on manhole covers.Absolute age dating: Have students work alone or in pairs to find an article or paper that uses radiometric age dating.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.
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I also like this simple exercise, a spin-off from an activity described on the USGS site above.