RADIOACTIVE ISOTOPES ARE UNSTABLE VERSIONS OF NORMAL ELEMENTS.BECAUSE THEY ARE UNSTABLE THEY GIVE OFF RADIATION TO TRY TO BECOME NORMAL.THE MORE STABLE FORM IT TURNS INTO IS CALLED THE DAUGHTER ELEMENT.One argument in favor of the absolute dating methods presented in the preceding articles is that they should work in principle.The first method of finding the absolute age of an object is by examining tree rings.If we looked at a cross-section ofa tree or log we would notice that all through it are concentric circles radiating out from the center to the bark. Each ring is also different, and the thickness of each ring is representative of the length of the growing season.Based on the known rates of deposition, we may therefore at least say that the depths of marine sediment found on the sea floor are consistent with the ages of the igneous rocks beneath them as produced by radiometric dating.
VARVES ARE LAYERS OF LIGHT AND DARK SEDIMENT THAT SHOW YEARLY CYCLES. Each spring or summer when the glacier was melting the glacier deposits a ton of sediment it was carrying into strems of water that are melting off of it.Now if we estimate the age of the sea floor like that, then we get a good agreement with the dates produced by radiometric methods.It is hard to think that this is a coincidence; it is also hard to think of any mechanism that could produce this agreement other than that the rocks are as old as radiometric methods tell us.So if our methods of radiometric dating are correct, then we would predict that rocks dated to the same age would have the same polarity, which they do.If this does not completely prove that radiometric dating is correct, it does at least show that (barring a wildly improbable coincidence) there is at least a one-to-one relationship between the dates produced by radiometric methods and the true dates, and so it must be taken as an argument in favor of these methods.
When the meltwater reaches a lake the heaiest sediments (sand and silt) sink to the bottom quickly and eventually formed thick layers of light colored rock.