Dating rocks and fossils using radioisotopes

Carbon-14 has a half-life of 5,730 ± 40 years, meaning that every 5,700 years or so the object loses half its carbon-14.Samples from the past 70,000 years made of wood, charcoal, peat, bone, antler or one of many other carbonates may be dated using this technique.Carbon-14, or radiocarbon, is a naturally occurring radioactive isotope that forms when cosmic rays in the upper atmosphere strike nitrogen molecules, which then oxidize to become carbon dioxide.

dating rocks and fossils using radioisotopes-11dating rocks and fossils using radioisotopes-32

For example, fission track dating measures the microscopic marks left in crystals by subatomic particles from decaying isotopes.

Another example is luminescence dating, which measures the energy from radioactive decay that is trapped inside nearby crystals.

Carbon-14 is also passed onto the animals that eat those plants.

After death the amount of carbon-14 in the organic specimen decreases very regularly as the molecules decay.

These rates of decay are known, so if you can measure the proportion of parent and daughter isotopes in rocks now, you can calculate when the rocks were formed.

Because of their unique decay rates, different elements are used for dating different age ranges.

The atoms of some chemical elements have different forms, called isotopes.

These break down over time in a process scientists call radioactive decay.

Though still heavily used, relative dating is now augmented by several modern dating techniques.

Radiocarbon dating involves determining the age of an ancient fossil or specimen by measuring its carbon-14 content.

When ‘parent’ uranium-238 decays, for example, it produces subatomic particles, energy and ‘daughter’ lead-206.