Radiometric Dating |
Author: Guillermo Rocha Edited for the web: Guillermo Rocha |
Radiometric dating uses the predictable decay rates of unstable isotopes (parent atoms) into stable isotopes (daughter atoms) to determine the age of rocks, fossils, and other materials, acting as a natural "atomic clock". The process involves measuring the ratio of parent to daughter atoms and applying the isotope's known half-life to calculate the time since the material formed or solidified. Key methods include Uranium-Lead dating for ancient rocks, Potassium-Argon dating for volcanic rocks, and Carbon-14 dating for recent organic materials. |
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HOW IT WORKS?
Radioactive Decay: Radioactive isotopes, or parent atoms, are unstable and naturally decay into stable isotopes, or daughter atoms, at a constant, predictable rate. |
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| The Half-Life: This decay rate is measured as the "half-life," which is the time it takes for half of the parent atoms in a sample to decay into daughter atoms. |
| The "Atomic Clock" starts when an igneous rock forms from magma or a living organism dies, the radioactive clock starts with 100% parent atoms and 0% daughter atoms. |
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HOW DO ATOMS CAN MEASURE HOW MUCH HAS ELAPSED?
HOW DO ATOMS CAN MEASURE HOW MUCH HAS ELAPSED?
By measuring the ratio of the remaining parent atoms to the newly formed daughter atoms in a sample, scientists can determine how many half-lives have passed since the material's formation. | |
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Calculating Age: Knowing the half-life for the specific isotope, scientists can then calculate the age of the material. | |
COMMON METHODS AND APPLICATIONS
COMMON METHODS AND APPLICATIONS
The Uranium-Lead (U-Pb) Dating is used for dating ancient rocks and minerals, including dating rocks as old as the solar system. Also, the Rubidium-Strontium (Rb-Sr) Dating is another method used for dating older rocks and minerals. | |
The Potassium-Argon (K-Ar) Dating is used for dating volcanic rocks and minerals. When a volcanic rock cools, any existing argon gas escapes, and the argon present must have come from the decay of potassium, providing a reliable "clock". | |
The Radiocarbon (Carbon-14) Dating is used for dating organic materials like bone, wood, and charcoal up to about 50,000 years old. Carbon-14, an isotope of carbon, decays into nitrogen-14. | |
Radiometric Dating has many advantages: unlike other methods that provide relative ages, radiometric dating provides an absolute (or numerical) age for a sample. Also these dates can be cross-checked by using different isotopes can be used within the same rock to provide cross-checks and increase accuracy, as seen with the Uranium-Lead system. Radiometric dating is highly reliable and tested. Scientists have extensively tested radiometric dating, and its results are extremely consistent with other dating methods, stellar evolution models, and astronomical observations. |
