There is no independent natural clock against which those assumptions can be tested.For example, the amount of cratering on the moon, based on currently observed cratering rates, would suggest that the moon is quite old.For example, a geologist may examine a cutting where the rocks appear as shown in Figure 1.Here he can see that some curved sedimentary rocks have been cut vertically by a sheet of volcanic rock called a dyke.There are more than 80 such technologies that are claimed to work.
Although age indicators are called ‘clocks’ they aren’t, because all ages result from calculations that necessarily involve making assumptions about the past.
by Tas Walker A geologist works out the relative age of a rock by carefully studying where the rock is found in the field.
The field relationships, as they are called, are of primary importance and all radiometric dates are evaluated against them.
It is clear that the sedimentary rock was deposited and folded before the dyke was squeezed into place.
By looking at other outcrops in the area, our geologist is able to draw a geological map which records how the rocks are related to each other in the field.