Radiometric Dating
What is the evidence? Measurements of the radioactive decay of unstable isotopes of elements (such as carbon, uranium, potassium, and hafnium) contained in rocks
What does it tell us? Absolute age—the date at which a material formed or a process occurred
Key limitations: Different radiometric dating methods have different limitations. For example, zircons, which are very stable minerals highly resistant to weathering, can be dated by measuring the decay of uranium-238 into lead-206. However, the date obtained is for the zircon mineral itself, not the sedimentary rock it is found in. The age of a sample could also have been “reset” by later events (such as impacts) and therefore not reflect the original age at which it formed.
Example: Dating Planets
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Zircons in the Jack Hills in Western Australia have been dated to be 4.4 billion years old. The video describes how scientists determine the age of rocks.
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