Radioactive decay and dating updating arraycollection
Zircons are nearly perfect clocks because we can be relatively certain that when the crystal formed, no lead was present and that means that when we discover ancient zircons in rocks today, we can be relatively confident that any lead present is the result of radioactive decay.
At the same time, the amount of the element that it decays into (in this case lead-207), will increase accordingly, as shown below. At what point on the graph would you expect the ratio of uranium to lead to be about 39 to 61?Now imagine that you have a rock sample that contains 39% uranium-235 and 61% lead-207. At around 1000 million years (i.e., one billion years), as shown on the graph at right above.Thus, you would calculate that your rock is about a billion years old.To see how it works, we'll start at the beginning, using uranium as an example: At left, a zircon crystal in a thin section cut from granite. Crystal structure image adapted fromadapted from Materialscientist CC Attribution-Share Alike 3.0 Unported Tens to hundreds of thousands of years before a major volcanic eruption, magma builds up beneath the surface of the Earth.In the magma, crystals of zirconium silicate (called zircons), as well as other crystals, form.
Radioactive decay Radioisotopic dating relies on the process of radioactive decay, in which the nuclei of radioactive atoms emit particles.