The carbon-14 it contained at the time of death decays over a long period of time.
By measuring the amount of carbon-14 left in dead organic material the approximate time since it died can be worked out.
Another role of isotopic geochemistry that is of great importance in geology is radiometric age dating. Beginning with studies in the 1950s, a much better chronology and record of Pleistocene climatic events have evolved through analyses of deep-sea sediments, particularly from the oxygen isotope record of the shells of microorganisms that lived in the oceans.
In August of 1993, with geologist Dr Steven Austin and others from the Institute for Creation Research, I climbed into the crater of Mount St Helens to view the lava dome.
Scientific knowledge of Earth’s geologic history has advanced significantly since the development of radiometric dating, a method of age determination based on the principle that radioactive atoms in geologic materials decay at constant, known rates to daughter atoms.It sits directly over the volcanic vent at the south end of the huge horseshoe-shaped crater that was blasted out of the mountain by the spectacular eruption on .From the crater, the dome appears as a huge steaming mound of dark, block-like rubble.The results showed that Ötzi died over 5000 years ago, sometime between 33 BC. Uranium has a very long half-life and so by measuring how much uranium is left in a rock its approximate age can be worked out. In 1905, shortly after the discovery of radioactivity, the American chemist Bertram Boltwood suggested that lead is one of the disintegration products of uranium, in which case the older a uranium-bearing mineral the greater should be its proportional part of lead.There's a small amount of radioactive carbon-14 in all living organisms.When they die no new carbon-14 is taken in by the dead organism.It's this resetting process that gives us the ability to date rocks that formed at different times in earth history.A commonly used radiometric dating technique relies on the breakdown of potassium (Ar in an igneous rock can tell us the amount of time that has passed since the rock crystallized.Dacite lava is too thick to flow very far, so it simply piled up around the vent, forming the mountain-like dome, which now plugs the volcanic orifice.Radioactive elements were incorporated into the Earth when the Solar System formed.Radioactive decay occurs at a constant rate, specific to each radioactive isotope.Since the 1950s, geologists have used radioactive elements as natural "clocks" for determining numerical ages of certain types of rocks. "Forms" means the moment an igneous rock solidifies from magma, a sedimentary rock layer is deposited, or a rock heated by metamorphism cools off....calculation was based on the assumption that the substance of the Earth is inert and thus incapable of producing new heat.