Sedimentary rock layer B exists between two other layers of sedimentary rock, layers A and C. The ordering of layers A and C has not been altered since disposition, and the layers have not been overturned. Base on this information, what can be concluded with certainty?

The information presented indicates that C is the oldest layer; it was deposited first. Layer B is above C so it is younger than C. Layer A is the last to be deposited so it is the youngest of the three layers.

Tectonic forces can sometimes disturb the natural order in which rocks have been deposited; they can be uplifted and overturned. When rock layers have been disturbed over time and does not show the correct sequence of deposition, it is known as an unconformity.