Relative dating sequence of events
With out individual time stamps the process of dating these structures could become extremely difficult.
To deal with many of these problems geologists utilize two types of geologic time: relative time and absolute time.
Inclusions: Inclusions, which are fragments of older rock within a younger igneous rock or coarse-grained sedimentary rock, also facilitate relative dating.
Inclusions are useful at contacts with igneous rock bodies where magma moving upward through the crust has dislodged and engulfed pieces of the older surrounding rock.
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.
Relative time places events or formations in order based on their position within the rock record relative to one another using six principles of relative dating.
Some rock-forming minerals contain naturally occurring radioactive isotopes with very long half-lives unaffected by chemical or physical conditions that exist after the rock is formed.This means that a quartz sandstone deposited 500 million years ago will look very similar to a quartz sandstone deposited 50 years ago.Making this processes even more difficult is the fact that due to plate tectonics some rock layers have been uplifted into mountains and eroded while others have subsided to form basins and be buried by younger sediments.Geologists generally know the age of a rock by determining the age of the group of rocks, or formation, that it is found in.The age of formations is marked on a geologic calendar known as the geologic time scale.