History of geology

The Geology, which is the study of the terrestrial phenomena underground and these resultants like the irruption of the volcano, the presence of metals, the earthquakes, interested the men since the Antiquité. Besides one finds illustrations of a volcanic interruptive phenomenon to the Neolithic with the execution of a mural of a Volcan at two tops, probably the Mont Hassan, with Çatal Hüyük (Turkey) and going back to.

Antiquity

Several theories, or mix the religious beliefs and observations are born at that time, in Occident, in ancient India, China. The mineralogy and of the volcanicity do not have for old the any report/ratio, while the bad interpretation of the presence of Fossile S, by Théophraste, a disciple of Aristote, will remain in commonly allowed until the scientific revolution of the XVIIe century. The work of this old Greek scientist, translated into Latin and in other languages, was used as reference during nearly two thousand years.

The appearance and the development of the Christianisme, will not support this science which are either of the manifestations of the anger of God, or like works of Satan. In addition the right interpretation of the fossils, by contradicting the Genesis, was not at all in sight. Let us recall finally that the Christians, as the people Indo-European placed the Enfer S, a world of flame, in the center of the Earth.

Emergence of the modern theories

In China, the scholar Shen Kuo (1031 - 1095) observed marine fossils in the various geological layers of the mountain have-hang You Shan which is to several hundred kilometers of the sea nearest. He deduced from it correctly that these mountains were at one time located at the sea level:
“I saw shells of bivalves in a horizontal layer, crossing a cliff. This lays down fossils was at one time given at the seaside, although the sea is now to several hundred kilometers more in the East. ”
But its assumption gained Europe later only many centuries. He also thought that the fossil plants were evidence of changes occurred in the climate.

In Europe

Large humanistic the Georg Bauer known as Georgius Agricola (1494 - 1555) summarized mining and metallurgical knowledge of its time in its more famous Re work “metallica libri xii” which appeared in a posthumous way in 1556. This last comprises also an appendix entitled Buch von den Lebewesen unter Tage (Book of the underground creatures). It treats in particular wind energy and hydrodynamics, transport and cast iron of the Minerai S and extraction of various layers, and thus constitutes a true metallurgy treaty. Actually, the work of Agricola which perhaps interests more geology was published in 1544 pennies the title In 1544 Of ortu and causis subterraneorum ; it there criticized the old assumptions and posed the first foundations of what was going to become later the physical Géologie. At the dawn of the XVIIe century, Jean-Etienne Guettard and Nicolas Desmarest surveyed the center of the France and recorded their observations on a geological map, underlining the volcanic origin of this area.

Geology ran up a long time against the dogma of the Église Catholique concerning the age of the Earth. Indeed, it concept-key of geology is the lasted , and the first scientific observations contradicted directly biblical teaching such as it is in the first chapter of the Old Testament, treating Genèse; it is known as there that the Earth was created in six days.

The Scot James Hutton (1726 - 1797) is regarded as the founding father of modern geology. In 1785, it off presented an article entitled Theory the Earth; however year observable Investigation off the Laws in the Composition, Dissolution and Restoration off Land upon the Earth which was published in 1788 in the “Transactions off the Royal Society off Edinburgh”. This article, in a practically unchanged form, constitutes the first chapter of its work published in 1795 in two volumes, heading Theory off the Earth, with Proofs and Illustrations (Theory of the Earth, with Preuves and Illustrations). One can consider that it acts-there of the first modern treaty of geology since Hutton exposes to it the principles of Uniformitarisme and of Plutonisme. The new geological theory that Hutton proposes implies that the Earth must be much older than than one supposed before. Indeed, time that the mountains put to erode, and the time which put the sediments to form of new rocks under the sea, which in their turn will be raised and emerged, cannot amount to millenia, but must amount of tens or hundreds of million years. Hutton was without question an enquiring brilliance, but it presented its written ideas in a too confused and too complicated way so that its brilliant work was immediately included/understood. It is his/her friend, the Scottish mathematician John Playfair (1748 - 1819), which made of it a talk clear and accessible to many people in its book Illustrations off the Huttonian Theory off the Earth , appeared in 1802. It is thanks to this digest of Playfair that the theory of Hutton was known and finally accepted by a growing number of geologists, among which will appear the Scot Charles Lyell. The successors of Hutton were known under the name of plutonists , because they thought that the rocks were formed by a deposit of lava produced under ground in Volcan S. They were opposed in that to the neptunists which thought that the rocks had been formed in a large ocean whose level dropped during time. Although defending essentially of the theses neptunists, Georges Vat (1769 - 1832) and Alexandre Brongniart (1770 - 1840) postulated in 1811 them also a very large age for the Earth. Their theory was inspired by the discovery of Vat of fossils of elephant S with Paris. To support their thesis, they formulated the stratigraphic principle according to which superimposed geological layers represent a succession in time. However, it should be noted that they were not the first to state apparently the basic principle of the Stratigraphie, since they were, without their knowledge, preceded by Nicolas Stenon (1638-1686) and by William Smith (1769 - 1839) which drew some of the first geological maps and began the scheduling of the geological layers of England and of Scotland by examining the fossils which was contained there.

Sir Charles Lyell (1797 - 1875) published the first edition of its Principes of Geology in 1830, qu' it updated by new editions until its death in 1875. He thought rightly that the geological processes were slow and had taken place during all the Histoire of the Earth, and continued same manner at the present time. This theory, the Actualisme, is to be opposed to the Catastrophisme according to which the terrestrial characteristics were formed and evolved/moved thanks to a succession of catastrophic events. Although the observations contradict this idea, the creationnists always now refuse to refute the biblical writings. It should be noted that work of Lyell, and the principles of relative chronology well-known and developed well at the time, led Charles Darwin (1809 - 1882) to publish in 1859 its monumental, and crucial work for the ideas philosophical, entitled The Origin off Species (the origin of the species) and later, in 1871, its not less important work concerning the ancestors of humanity ( The Descent off Man, and Selection in Relation to Sex ). The observation of fossils in the summit meeting of the Andes and their base pushed this author to be wondered about the continuation of the events which had been able well to lead to this disparate distribution.

At the 19th century, geology thus leant seriously on the thorny question of the age of the Earth. The estimates oscillated between hardly a hundred and thousand years until several billion years. The geological community could, however, mean itself on the fact that the Earth was at least to have several hundreds of million years. At that time the physicists, and in particular the very influential Lord Kelvin, hardly accepted this estimate. Indeed, using the laws of the Thermodynamic , Lord Kelvin had calculated that the Earth, while cooling gradually since its formation, was to be at most fifty thousand years old. This result is unattackable if one omits to consider, as Kelvin did it, of the internal energy sources to the Earth other than heat resulting from the gravific contraction. It is the discovery of the radioactivity, in 1896, by Henri Becquerel and Pierre and Marie Curie who made change the things and put the estimates of the physicists of the age of the Earth in agreement with those of the geologists, by them specifying later well more than do not allow it stratigraphy.

A new projection, called “revolutionist” by certain geologists, took place in geology in the years 1960. It is of the development and acceptance by the scientific community of the Plate tectonics . This one consists of a revitalization of the theory of the continental drift, proposed as of 1912 by the German meteorologist Alfred Wegener (1880 - 1930), but rejected from the start by the major part of the geologists (DuToit in South Africa and Holmes in Scotland constitutes notable exceptions) and the totality of the geophysicists. Actually, the theory of Wegener sinned by two weak points:

  1. with the geodetic methods of the time, it was impossible to highlight the drift of two continents one compared to the other
  2. nobody did not manage to explain the forces able to drive continents through the subjacent medium resisting.

The elements which finally suggested, with Canadian William Jason Morgan and with French Xavier Pichon, the concept of rigid plates transported by movements of convection in the great depths of the Earth to the way in which people and objects on the travelators are conveyed are:

  • paleomagnetic measurements,
  • the cartography of the underwater funds for commercial and military needs,
  • recognition of the médio-oceanic dorsals and that of the expansion of the oceanic funds,
  • the cartography of the seismic epicentres on a worldwide scale.

The forces able to make move whole continents thus find their origin in the great reserve of heat inside the Earth.

The theory of the plate tectonics has the advantage of gathering geologists, geophysicists and geodesists in the same company of which the goal is to know our planet better and better. The geologists contribute to it by their observations on the ground, the seismologists by the study which they make of the mechanisms producing the earthquakes, the geodesists by the increasingly precise determination of the undulations geoid and gravimetric anomalies attached there, and geodynamicians by a mathematical modeling of the currents of convection inside the Earth. But it should not be forgotten that it is at present always about a theory which presents many gaps and weaknesses, even if its essential points seem definitively acquired. In addition, in spite of the passion of the young geologists for this theory, many which is those will always have, was this only to earn their living in a service geological or an unspecified company of prospection, to make “geology of dad”, i.e. to take samples of rock on the ground, to know to draw up and interpret geological maps with the local scales or regional and, possibly, to be capable to make use of measuring instruments which the geophysicists place at their disposal.

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