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Radiometric Dating

Radiometric methods can date much older inorganic materials by using the decay of radioactive isotopes. By measuring the ratio of parent to daughter isotopes and calculating the half-life of the parent isotope, scientists can measure the age of the material.

Core Issue:

The Bible suggests that the earth is only a few thousand years old, yet radiometric dating suggests that organic materials are billions of years old.

Methods

Examples

Item Measured Age Dating Method Additional Information
Mt. Vesuvius eruption 1,950 years old K-Ar Dated rocks from the 79 CE eruption
Hominid fossils (Sterkfontein, South Africa) 3.4-3.7 million years old U-Pb Dated flowstones associated with Australopithecus fossils
Oldest known rock on Earth (Canada) 4.03 billion years old U-Pb Nuvvuagittuq greenstone belt in Quebec
Martian meteorite ALH84001 4.09 billion years old Rb-Sr Meteorite found in Antarctica, believed to be from Mars
Moon rocks (Apollo missions) 3.16-4.54 billion years old Multiple methods Various samples collected during Apollo missions
Acasta Gneiss (Canada) 4.03 billion years old U-Pb One of the oldest known intact crustal fragments on Earth
Allende meteorite 4.567 billion years old Pb-Pb One of the most studied meteorites, fell in Mexico in 1969
Murchison meteorite 4.565 billion years old Rb-Sr Carbonaceous chondrite that fell in Australia in 1969
Pre-solar grains Up to 7 billion years old Various methods Microscopic grains found in meteorites, older than the solar system
A Concordia diagram

A Concordia diagram from Cornell showing the decay of parent uranium/lead isotopes to daughter uranium/lead isotopes.
The chart also shows known half-life decay rates in Ga's (billions of years).

Radiometric dating of a rock

A real-world example of a Concordia diagram. Radiometric data taken from Geochron.
The chart shows that this sandstone most likely formed between 2.8 and 3.1 billion years ago.