If the rock layers are no longer horizontal, this is because of changes in the environment that occurred after the formation of the sedimentary rock.
The law of superposition states that for any selected rock layer, the layer above is typically younger than it is and the layer below is generally older than it is.
By studying relative dating, you prepare yourself to make your own insights about different kinds of ancient environments and biomes on the APES exam.
Relative dating is the process of establishing a sequence of historical events and relative ages of rocks by looking at sedimentary rock formations and their features.
Index fossils are incredibly useful in relative dating.
Because of their boom-and-bust qualities, the presence of an index fossil can be used to assign a relative age to sedimentary rocks in which the fossil occurs.
That is, they become abundant, and then their sensitivity to environmental changes causes them to become extinct.
Since many plants and animals have large habitats, this can be very useful in helping to date sediment layers of interest.
Fossils are any preserved remains or traces of an organism that previously lived.
Unlike absolute dating, relative dating does not assign specific years to individual events.
Instead, it seeks to establish which actions occurred where in a sequence of geologic events.
However, since environments change over time, this is not a perfect way of determining geologic age.