The abundance and variety of fossils in Phanerozoic rocks have allowed geologists to decipher in considerable detail the past 600 million years or so of the Earth’s history.

facts about radiometric dating-19

Three basic approaches are used to determine the age of the Earth.

The first is to search for and date the oldest rocks exposed on the surface of the Earth.

The best evidence is contained in the Earth’s incomplete and complex but accurate stratigraphic record — a record that has been the subject of nearly two centuries of study.

Slowly and painstakingly, geologists have assembled this record into the generalized geologic time scale shown in Figure 1.

All the major continents contain a core of very old rocks fringed by younger rocks.

These cores, called Precambrian shields, are all that remain of the Earth’s oldest crust.efore analyzing the arguments advanced by creation “scientists” for a very young Earth, I here summarize briefly the evidence that has convinced scientists that the Earth is 4.5 to 4.6 billion years old.There can be no doubt about the Earth’s antiquity; the evidence is abundant, conclusive, and readily available to all who care to examine it.This was done by observing the relative age sequence of rock units in a given area and determining, from stratigraphic relations, which rock units are younger, which are older, and what assemblages of fossils are contained in each unit.Using fossils to correlate from area to area, geologists have been able to work out a relative worldwide order of rock formations and to divide the rock record and geologic time into the eras, periods, and epochs shown in Figure 1.Before reviewing briefly the evidence for the age of the Earth, I emphasize that the formation of the Solar System and the Earth was not an instantaneous event but occurred over a finite period as a result of processes set in motion when the universe formed.