Sedimentary rocks are formed particle by particle. Over time, layers of particles are piled one on top of the other.
Therefore, in any sequence of layered rocks, a given layer
must be older than any layer on top of it. This is known as
the law of superposition. This law is fundamental to the
interpretation of Earth's history because it indicates the
relative ages of rock layers and the fossils in them. What
evidence would support the law of superposition?
a. An earthquake occurs so that the rock layers are
disturbed.
b. Sedimentary rock gradually turns into another type of
rock.
c. Fossils in higher layers are not as advanced and
complex as the fossils in lower layers of sedimentary
rock.
d. Radiometric dating shows that fossils in lower layers
are older than fossils in higher layers of sedimentary
rock.