There are many natural phenomena which evolutionary geologists say require many thousands or even millions of years to bring about. However, creationists have long held that most geologic processes can take place quickly if the conditions are right. Some of these phenomena include formation of the Precambrian granite "basement" rocks of the earth's crust, radioactive decay, canyon formation, petrified forest formation, coal formation, the rapid laying down of several successive sedimentary layers, formation of clastic dikes, formation of vast fossil graveyards, and stalagmite and stalactite formation.
Evidence for the rapid formation of the granite basement rocks of the continents has come from the study of polonium radiohalos.1 Polonium is one of several elements in the uranium radioactive decay chain which ends in lead. Polonium decays by emitting alpha particles (helium nuclei) with kinetic energies characteristic of polonium. The alpha particles penetrate the surrounding rock, eventually coming to rest and converting into helium gas by picking up two electrons from the environment. The rock is discolored at the location the alpha particle comes to rest. After enough alpha particles have been emitted, a sphere of discoloration results. Cross sections of the sphere appear as a ring that is called a radiohalo. Eventually the decay products of polonium will be converted into lead. The lead formed can be analyzed for its isotopic composition. Different elements give different halo patterns and different lead isotope products.