4 rules of relative dating
Metamorphic rocks may also be radiometrically dated.
However, radiometric dating generally yields the age of metamorphism, not the age of the original rock.
Relative dating techniques provide geologists abundant evidence of the incredible vastness of geologic time and ancient age of many rocks and formations.
However, in order to place absolute dates on the relative time scale, other dating methods must be considered.
Geologists generally know the age of a rock by determining the age of the group of rocks, or formation, that it is found in.
Though relative dating can only determine the sequential order in which a series of events occurred, not when they occurred, it remains a useful technique.For example, shells, wood, and other material found in the shoreline deposits of Utah’s prehistoric Lake Bonneville have yielded absolute dates using this method.These distinct shorelines also make excellent relative dating tools.Faunal Succession: Similar to the law of superposition is the law of faunal succession, which states that groups of fossil animals and plants occur throughout the geologic record in a distinct and identifiable order.Following this law, sedimentary rocks can be “dated” by their characteristic fossil content.
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Development of the geologic time scale and dating of formations and rocks relies upon two fundamentally different ways of telling time: relative and absolute.