By: Isabella Chen
I’m pretty sure all of us have gone through the dinosaur/fossil faze when we were younger. Unless you’re like Ross Geller, and never grew out of it (just kidding, no shame to those who are paleontologists). We were handed down that information pretty easily like the name/type of dinosaur, diet, size, and age. Now, paleontologists can learn a lot from the bones/remains of dinosaurs and fossils, but determining the age can be a bit difficult. That’s why this method called Radiometric Dating/Decay helped determine the actual age of a rock.
Radiometric Dating is a dating technique that calculates an age of geologic materials by measuring the presence of a short-life radioactive element. Some of the elements involved in this technique are Uranium-234, Carbon-14, and Potassium-40. Certain elements are more reactive to certain rocks, but I will explain that later. There are 3 types of radiometric decay: beta decay, beta-plus decay, and alpha decay.
Beta Decay is when a neutron turns into a proton. There is no charge, but then it goes into having a positive charge, meaning that a negative charge would then have to be released. The mass does not change, since an electron has almost no mass. The atomic number does go up by 1. An element to use for example is Carbon-14 (atomic number 6) becoming Nitrogen-14 (atomic number 7). Beta-plus Decay is when an electron is added, changing the proton into a neutron. So the atomic number would go down by 1. An example would be Potassium-40 (atomic number 19) becoming Argon-40 (atomic number 18). Alpha Decay is when the nucleus spits out an alpha particle. An alpha particle consists of 2 protons and 2 neutrons. The atomic number decreases by 2 and the mass decreases by 4. An example would be Uranium-234 decays to Thorium-230. All radiometric decay happens under the same rate and same type of mathematical expression, exponential curve. They use the method called half-life. The half-life of radiometric material is transformed into stable isotopes. On top of that, the half-life is constant forever.
Back to certain elements being more reactive to certain rocks. You can use a parent/daughter pair to date something as old as 6 or 7 half-lives. So for example Uranium-235 and Lead-206 have a half-life of up to 4.5 billion years, meaning it can help date a rock that is 4.3 billions years old.
Overall, Radiometric Dating is super helpful for scientists to help determine the absolute age of rocks/fossils, and is the reason why we have dates for our geologic time scale. Radiometric dating also provides the rates of evolutionary changes. To see if anything significant had happened and allow scientists to hypothesize on certain events leading up to the evolutionary change. For students in OnRamps Earth, Wind, and Fire, we should thank scientists for creating the dating technique Radiometric Dating, as it allows us students to be successful in understanding the age of Earth, and what was once living on this planet before humans existed.
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