Radioisotope dating audio
Radioactive decay Radioisotopic dating relies on the process of radioactive decay, in which the nuclei of radioactive atoms emit particles.
This releases energy (in the form of radiation) and often transforms one element into another.
For practice, use the graph above to estimate the age of a rock sample that contains 10% uranium and 90% lead.
The example above describes uranium/lead decay, which happens very slowly; however, different radioactive elements have different half-lives. This allows scientists to date events that are more or less ancient.
These zircon crystals are tiny just a tenth of a millimeter long but they are the key to uranium-lead dating.
If these crystals were pure, they would contain just zirconium, silica, and oxygen; however, uranium happens to have a similar arrangement of outer electrons to zirconium, and so as zircons form, "mistakes" are sometimes made, and uranium is substituted for zirconium.
This suite of techniques allows scientists to figure out the dates that ancient rock strata were laid down and hence, provides information about geologic processes, as well as evolutionary processes that acted upon the organisms preserved as fossils in interleaved strata.When the eruption occurs, zircons are released in the ash and lava, which then become rocks like rhyolite.Geologists hunt for these particular sorts of rock to date the volcanic eruption in which the rock formed.Thus, when a geologist dates a rock using uranium-lead dating, he or she is actually getting an estimate on the age of its zircon crystals, which formed "shortly" before the volcanic eruption.
Of course, in this case "shortly" is meant in terms of geologic timescales.Slightly different dating techniques are used with different radioactive elements, but the same basic logic of estimating backwards based on radioactive decay remains the same.