The oldest and most widely used dating method in archaeology is typological dating.
An artefact is dated on the basis of knowledge about the age of other similar artefacts.
Once we have dated a sufficient number of rocks and found out whether they have normal or reverse polarity, we can likewise build up a timeline for the occurrence of the reversals.
Four main methods have been used in Willandra archaeology.
This well known method was the first technique that became available for accurate dating of old materials.
So if we are presented with an undated rock, and we find a really distinctive pattern of paleomagnetic reversals within it, we may be able to identify the one time at which such a sequence of magnetic reversals took place.
The reader will observe that it is necessary to be able to date some rocks, in fact a lot of rocks, before paleomagnetic dating can be brought into play.
After the second half-life has elapsed, yet another 50% of the remaining parent isotope will decay into daughter isotopes, and so on.
For all practical purposes, the original isotope is considered extinct after 6 half-life intervals. A small portion of a meteorite is vaporized in the device forming ions.
Simply counting the number of rings will give one a fairly good idea of the age of the tree.
Periods of heavy rain and lots of sunshine will make larger gaps of growth in the rings, while periods of drought might make it difficult to count individual rings. When a given quantity of an isotope is created (in a supernovae, for example), after the half-life has expired, 50% of the parent isotope will have decomposed into daughter isotopes.
In this article we shall discuss how we can use the paleomagnetism in rocks to attach dates to them (paleomagnetic dating).