July 6, 2022

In geology, Neptunism is a discarded and obsolete scientific theory, proposed by Abraham Werner at the end of the 18th century, which attributed the origin of rocks to the crystallization of minerals in the oceans,[1] in an early period after creation. . The theory got its name from Neptune, the ancient Latin name for the Greek god of the seas: Poseidon. Immediately after its publication, the new proposal sparked a heated debate between Werner's supporters and those who believed in plutonism, an antagonistic theory that attributed the origin of geological material to the action of volcanoes. Plutonism, suitably adapted, would replace Neptunism as the dominant theoretical line; especially when, at the beginning of the 19th century, the concept of uniformity seemed to respond better to the discoveries made in the area of ​​geology. Many rock-forming processes are now known, and the process that generates sedimentary rock is considered to be quite similar to those described by proponents of Neptunism.

Historical development

In the mid-eighteenth century, the study of fossils led geologists and naturalists to question the scientific validity of Natural History raised in the book of Genesis. Georges-Louis Leclerc de Buffon dated the origin of the earth to 75,000 years ago —although he admitted that this figure could fall short— and documented a series of historical changes through different geological epochs. Abraham Gottlob Werner was then a mining inspector and professor of mining and mineralogy at the mining academy of Freiberg, (Saxony), the most important center for the study of geology during the 18th century. With his Brief Classification and Description of Rocks (1787) and his lectures, he established a new model of geological classification that was based on the sequences of superimposed layers instead of on the types of minerals, as had been conventional until now. . He based his conception of rock formation through a sequence of historical processes on the assumption that the originally water-covered planet had been formed by sedimentation on the seafloor. In this way, the planet had been formed from its core, from older and harder rocks – such as granite – to the weaker superficial layers, in which a large number of fossils were found. The worldwide flood described in the Bible had repeated the same process, adding new layers of light rocks on top of a more solid core. The influence of the volcanoes, therefore, was limited to a small addition of surface material, while the true generative process of the rock was carried out underwater.

The controversy between Neptunism and Plutonism/volcanism

An opposing theory, known as plutonism (or volcanism), held that rocks originated through high-temperature processes. This idea, first proposed by Anton Moro (1687-1750), was based on his studies of volcanic islands, and was assimilated by James Hutton in his uniformitarian theory, which described the origin of rocks as a constant process of erosion of the elements and regeneration of the material through pressure and temperature. The Neptunists differed from the Plutonists in their interpretation of the origin of basalt: For the former, the mineral was a sedimentary material that was partially composed of fossils, so it could not be of volcanic origin. Hutton was correct in stating that basalt did not contain fossils, as well as being impermeable, hard and crystalline. He found certain geological formations in which strata of basalt cut through layers of other minerals, reinforcing his assumption that the mineral originated from molten rock beneath the earth's crust. The debate did not stop at the