Radio dating rocks
The field relationships, as they are called, are of primary importance and all radiometric dates are evaluated against them.For example, a geologist may examine a cutting where the rocks appear as shown in Figure 1.Thus, he already ‘knows’ that the igneous dyke must be younger than 200 million years and older than 30 million years.(Creationists do not agree with these ages of millions of years because of the assumptions they are based on.) Because of his interest in the volcanic dyke, he collects a sample, being careful to select rock that looks fresh and unaltered.Here he can see that some curved sedimentary rocks have been cut vertically by a sheet of volcanic rock called a dyke.It is clear that the sedimentary rock was deposited and folded before the dyke was squeezed into place.
All rocks and minerals contain tiny amounts of these radioactive elements.C and counting the amount of each) allows one to date the death of the once-living things.Perhaps you have heard of Ice Man, a man living in the Alps who died and was entombed in glacial ice until recently when the ice moved and melted.He assumes therefore that Sedimentary Rocks A are the same age as the other rocks in the region, which have already been dated by other geologists.In the same way, by identifying fossils, he may have related Sedimentary Rocks B with some other rocks.