How does radiometric dating work
An hour glass is only useful if it is not disturbed.But after rocks crystallize from molten magma, they can be heated and cooled; they can be affected by metamorphic events and groundwater.He explores the geology of the area so he can understand the geological history, and where his particular sample fits into the sequence of geological events.He checks out the ages other geologists have assigned to the different rocks in the region.That’s because we did not observe what happened in the past when the rock formed.Neither can we travel into the past to make the necessary measurements. This is the fatal problem that essentially makes radioactive dating useless as a primary method for determining age. They may assume that different minerals in the rock originally had the same isotopic ratios to start with.In other words, the hourglass only works when we know its initial condition.
Other minerals may have grown inside the rock much later, during a time when the area was heated and metamorphosed.These geologic events can cause elements to be gained and lost to the rock.It’s like cracking the hourglass and having some of the sand leak out, or other sand leak in.Apart from the fatal problem of not knowing the initial conditions, there is another problem that is just as deadly.We don’t know what happened to the rock during its ‘lifetime’.