Geologic assessment of active tectonism depends on two key measures: the age and the amount of deformation of a given stratigraphic unit.
The amount of deformation can normally be measured with greater accuracy than the age.
Adequate age control is thus a limiting factor in studies of active tectonism.
About 26 dating techniques can be applied to dating deposits and deformation of late Cenozoic age (past few million years).
is, as mentioned earlier, the technique of piecing together the informational content of separated outcrops.
When information derived from two outcrops is integrated, the time interval they represent is probably greater than that of each alone.
Relative-dating techniques are nearly always applicable but are not precise and require calibration.
However, as previously noted, times of volcanism and metamorphism, which are both critical parts of global processes, cannot be correlated by fossil content.That only worked for sedimentary rocks, and only some of those.Rocks of Precambrian age had only the rarest wisps of fossils.A hundred years ago, our ideas about the ages of rocks and the age of the Earth were vague. Judging from the amount of rocks there are, plus the imperceptible rates of the processes forming them—erosion, burial, fossilization, uplift—the geologic record must represent untold millions of years of time.It is that insight, first expressed in 1785, that made James Hutton the father of geology.