Radioactive dating sample problems

They also measure the sand grains in the bottom bowl (the daughter isotope, such as lead-206 or argon-40, respectively).

Based on these observations and the known rate of radioactive decay, they estimate the time it has taken for the daughter isotope to accumulate in the rock.

After all, textbooks, media, and museums glibly present ages of millions of years as fact.

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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?

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.

Ra, a common isotope of radium, has a half-life of 1620 years.

Knowing this, calculate the first order rate constant for the decay of radium-226 and the fraction of a sample of this isotope remaining after 100 years.

Though they are very tiny, polonium radiohalos have a huge message that cannot be ignored.

They point to a catastrophic origin for granites, consistent with the biblical timeframe for earth history and God’s judgment during the Flood.

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.

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.

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