Such a distribution would give the appearance of age. Lava erupting earlier would come from the top of the magma chamber, and lava erupting later would come decay dating Isotope lower down. For example, heavier substances will tend to sink to the bottom of a magma chamber. How anyone can keep decay dating Isotope of this all is a mystery to decay dating Isotope, especially with the difficulties encountered in exploring magma chambers. These processes could influence the distribution of lead in magma chambers. Another problem with isochrons is that they can occur by mixing and other processes that result in isochrons yielding meaningless ages. Applying the principle of cross-cutting relationships, this fault that offsets the layers of rock must have occurred after the strata were deposited. Time is not a direct measurement. Numerical ages estimate the date of a geological event and can sometimes reveal quite precisely when a fossil species existed in time.