Final answer:
The Cliffs of the Niobrara Formation were created by the deposition of chalk from coccolithophore skeletons in a Cretaceous sea, not by volcanic eruptions or glaciation.
Step-by-step explanation:
The Cliffs of the Niobrara Formation in western Kansas were formed by deposits from the Cretaceous period, specifically due to the accumulation of calcium carbonate (chalk) from the 'skeletons' of coccolithophore organisms in a Cretaceous sea.
This process of formation differs from mechanisms such as Paleozoic volcanic eruptions, Cretaceous glaciation, or the erosional forces seen at the Vermillion Cliffs. These deposits are similar to the well-known white cliffs of Dover and show the common process of sedimentary deposition in a marine environment.