Dating a prehistoric find
Despite seeming like a relatively stable place, the Earth's surface has changed dramatically over the past 4.6 billion years.
Younger layers are deposited on top of older layers (principle of superposition).
The principle states that any geologic features that cut across strata must have formed after the rocks they cut through (Figures 2 and 3).
According to the principle of original horizontality, these strata must have been deposited horizontally and then titled vertically after they were deposited.
In addition to being tilted horizontally, the layers have been faulted (dashed lines on figure).
Applying the principle of cross-cutting relationships, this fault that offsets the layers of rock must have occurred after the strata were deposited.