Neptunism: The ocean rocks

How do rocks form?

Neptunism is a theory that suggests all rocks formed in a primeval ocean through sedimentation. Proponents claimed this could explain why we find different types of rock in different layers of the earth. Volcanic phenomena were dismissed as being newer in earth's history and not relevant for understanding most rocks we can observe.

While intriguing, this theory did not stand the test of time as other types of rock formation were shown to be significant.