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But when we date the rocks using the rubidium and strontium isotopes, we get an age of 1.143 billion years.This is the same age that we get for the basalt layers deep below the walls of the eastern Grand Canyon.4 How could both lavas—one at the top and one at the bottom of the Canyon—be the same age based on these parent and daughter isotopes?There are similar problems with the other radioactive “clocks.” For example, consider the dating of Grand Canyon’s basalts (rocks formed by lava cooling at the earth’s surface).

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professional dating profile sample - Radioactive dating sample problems

One solution is that both the recent and early lava flows inherited the same rubidium-strontium chemistry—not age—from the same source, deep in the earth’s upper mantle.

This source already had both rubidium and strontium.

Radiometric dating measures the decay of radioactive atoms to determine the age of a rock sample.

It is founded on unprovable assumptions such as 1) there has been no contamination and 2) the decay rate has remained constant.

Similarly, as molten lava rises through a conduit from deep inside the earth to be erupted through a volcano, pieces of the conduit wallrocks and their isotopes can mix into the lava and contaminate it.

Because of such contamination, the less than 50-year-old lava flows at Mt.Obviously, these eruptions took place very recently, after the Canyon’s layers were deposited ().These basalts yield ages of up to 1 million years based on the amounts of potassium and argon isotopes in the rocks.No geologists were present when most rocks formed, so they cannot test whether the original rocks already contained daughter isotopes alongside their parent radioisotopes.For example, with regard to the volcanic lavas that erupted, flowed, and cooled to form rocks in the unobserved past, evolutionary geologists simply assume that none of the daughter argon-40 atoms was in the lava rocks.By dating rocks of known ages which give highly inflated ages, geologists have shown this method can’t give reliable absolute ages.

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