Science
Dinosaurs & Paleontology
Conceptual
11–13 yrs
Radiometric Dating
放射性测年法
Description
Explain how radiometric dating works — radioactive isotopes decay at a known rate (half-life), so measuring the ratio of parent to daughter isotope in a rock or fossil gives an absolute age; distinguish between carbon-14 (useful up to ~50,000 years) and uranium-lead (useful for millions to billions of years)
Mastery Evidence
- Defines half-life as the time for half the radioactive parent isotope to decay to the daughter isotope
- Explains that the parent:daughter ratio in a sample gives an estimate of absolute age
- Distinguishes carbon-14 (for recent organic material) from uranium-lead or potassium-argon (for deep geological time), explaining why carbon-14 cannot be used for dinosaur bones
Assessment Prompt
If your child was told a dinosaur bone was dated using uranium-lead radiometric dating, could they explain what that means — what is decaying, why the rate of decay is useful, and roughly why scientists don't use carbon-14 for 70-million-year-old bones?
