Scientists can determine the absolute age of rocks and fossils primarily through two methods:
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Radiometric Dating: This method relies on the decay of radioactive isotopes within the minerals of rocks and fossils. By measuring the ratio of parent isotopes to daughter isotopes and knowing the half-life of the parent, scientists can calculate the age of the sample. Common isotopes used in radiometric dating include Carbon-14 (for organic material), Uranium-238 (for older rocks), and Potassium-40.
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Dendrochronology: This technique involves counting the growth rings of trees, which can provide annual records of age. By analyzing these rings, scientists can determine the absolute age of wood samples and can even correlate them with climatic events. This method is particularly useful for dating relatively recent geological and archaeological samples.
Both methods provide critical insights into the timing of geological events and the age of fossils, helping researchers understand the history and evolution of life on Earth.