Final answer:
Radiometric chronometric dating techniques include radiocarbon dating for organic materials, uranium-lead dating for igneous rocks, and potassium-argon dating for older volcanic rocks, all of which are based on the known decay rates of radioactive isotopes.
Step-by-step explanation:
Three radiometric chronometric dating techniques used by geologists to determine numerical ages for rocks, minerals, and fossils include:
- Radiocarbon dating: This method utilizes the radioactive isotope carbon-14 to date organic materials. As living organisms cease to intake carbon when they die, the carbon-14 within them begins to decay at a known rate. By measuring the remaining carbon-14, scientists can determine when the organism died, effective for samples between 300 and 50,000 years old.
- Uranium-lead dating: This technique is often used to date zircon crystals in igneous rocks and involves measuring the decay of uranium isotopes into lead. The long half-lives of these isotopes make it suitable for dating geological formations that are millions to billions of years old.
- Potassium-argon dating: Ideal for dating older volcanic rock, this method measures the ratio of potassium-40 to argon-40. As potassium-40 decays into argon-40 at a known rate, this technique can determine the rock's formation age.
These radiometric dating techniques are based on the rate of decay of radioactive isotopes and are crucial tools for establishing absolute ages for geological and archaeological findings.