Radiometric dating
Also called: Radioactive dating · Topic: Continental Drift, Sea-floor Spreading and Plate Tectonics · NCERT: Class 11, Ch 4 "Distribution of Oceans and Continents"
Meaning
Radiometric dating finds the age of a rock from radioactive elements inside it, such as uranium and potassium. These elements break down (decay) at a steady, known rate, like a natural clock. By measuring how much has decayed, scientists can work out how old the rock is. This allowed rocks on different continents to be matched by age. It also showed that ocean-floor rocks are much younger than continental rocks.
Example
Radiometric dating showed that a belt of 2,000-million-year-old rocks on the coast of Brazil matches rocks of the same age in western Africa. This supports the idea that the two continents were once joined.
Don't confuse with
- Palaeomagnetism: Palaeomagnetism reads the direction of the earth's magnetic field locked in a rock when it formed. Radiometric dating tells the rock's age.
Related concepts
- Jigsaw fit of continents
- Rocks of the same age across oceans
- Tillite
- Fossil evidence for continental drift
- Mesosaurus