Fossils are dated using various scientific techniques, most often by measuring the amounts of particular radioactive elements present.
Radioactive Dating Methods Explained
Radioactive dating methods are crucial for determining the age of rocks and fossils. These methods rely on the predictable decay of radioactive isotopes.
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Radiocarbon Dating: This technique is used for dating organic materials (like bones or wood) up to around 50,000 years old. It measures the amount of carbon-14 remaining in the sample. Because carbon-14 decays at a known rate, scientists can calculate how long ago the organism died.
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Potassium-Argon Dating: This method is applied to older samples, typically rocks that are millions or billions of years old. It measures the decay of potassium-40 into argon-40. Since argon is a gas that escapes from molten rock but accumulates as the rock solidifies, the ratio of potassium-40 to argon-40 indicates the rock's age.
Different Dating Techniques Summarized
The following table summarizes common dating techniques.
| Dating Method | Materials Dated | Age Range | Principle |
|---|---|---|---|
| Radiocarbon Dating | Organic materials (bones, wood, etc.) | Up to 50,000 years | Measures the decay of carbon-14. |
| Potassium-Argon Dating | Rocks | Millions/Billions+ | Measures the decay of potassium-40 into argon-40. |
Why Use Radioactive Elements?
- Predictable Decay: Radioactive elements decay at a constant, known rate.
- Isotopic Abundance: The initial amount of radioactive isotopes can be estimated or inferred.
- Wide Applicability: Different radioactive elements are suitable for dating materials of varying ages. As the reference states, scientists "measure the amounts of particular radioactive elements—often radiocarbon or potassium—present to determine when a rock was formed, or when an animal or plant died."
