Radioactive isotopes in dating fossils
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.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.What’s more, if the whole rock is badly weathered, it will be hard to find an intact mineral grain containing radioactive isotopes.You might have noticed that many of the oldest age dates come from a mineral called zircon.Though still heavily used, relative dating is now augmented by several modern dating techniques.Radiocarbon dating involves determining the age of an ancient fossil or specimen by measuring its carbon-14 content.
Green plants absorb the carbon dioxide, so the population of carbon-14 molecules is continually replenished until the plant dies.
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.