Age Determination

Relative Age Determination - Narrows down the time frames by use of:

1.  Stratafications - The oldest rocks are on the bottom.

2.  Fossils

3.  Unconformities - Erosional contact
A)  non-conformity:  presence of rock that does not match up with surrounding rocks, usually igneous.
B)  angular unconformity:  the horizontal sedimentary rocks have been deformed to sit at an angle.
C)  disconformity:  a very large time span missing between 2 layers of rock

Absolute Age Determination - Tells a precise time frame for a layer of rock by use of the Radioactive Isotopes included in rock make-up:

The parent isotopes decay to become stable daughter products.  Absolute Age Determination compares the amount of parent/daughter cells to find out the age using already known half-lives.  It does not work on sedimentary rocks.