Final answer:
Radiometric dating calculates the numerical age of rocks and fossils using the decay of radioactive isotopes, while relative dating establishes the sequence of events without exact ages. Isotopic analysis of elements like rubidium and strontium assists in precise age determination that refines the geological time scale.
Step-by-step explanation:
Geologists employ various methods to date rocks and geological events. Radiometric dating is a technique used to determine the numerical age of a material. It is based on the decay rate of radioactive isotopes within rocks and fossils. To calculate an age, geologists first establish the half-life of the isotope in question and then measure the ratio of parent isotopes to daughter products in the sample. With this information, they apply a standard radiometric age equation to arrive at the age of the rock or mineral.
Relative dating, on the other hand, is a method used to determine the sequence of events without necessarily providing a numerical age. Techniques such as stratigraphy and the study of layering in sedimentary rocks are used to establish relative chronology. Relative dating is also useful for determining the rate of speciation of early organisms by examining fossils within different layers of rock.
For absolute age determinations, isotopes such as rubidium and strontium are analyzed to find the age of rocks, as seen in samples from places like Isua in Greenland. Knowing the decay constant and the ratio of isotopes allows geologists to accurately pinpoint the age of rock formations, contributing to our understanding of the geological time scale and the history of the Earth.