basic dating rules - Radiometric dating volcanic ash

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.

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.

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