Neptunism is a discredited and obsolete scientific theory of geology proposed by Abraham Werner in the late 18th century that proposed rocks formed from the crystallisation of minerals in the early Earth's oceans. It was named after Neptune, the ancient Roman name for the ancient Greek god of the sea, Poseidon. There was considerable debate between its proponents and those favouring a rival theory known as Plutonism which gave a significant role to volcanic origins, and in modified form replac… (More on Neptunism)