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Geology (from Greek γη- (ge-,
"the earth") and λογος (logos, "reason")) is the science and study of the earth, its history, and the processes that shape
it. The word was first used in this sense by Jean-André de Luc
in the year 1778 and introduced by Horace-Bénédict de Saussure in the year 1779 as a fixed
term. [An older sense of the word is first mentioned by Richard de
Bury in 1473. He used it to distinguish between earthly and theological
jurisprudence.]
Geology is also sometimes used about similar studies of other bodies of the solar system. However, specialised terms
such as selenology (studies of the Moon), areology (of Mars), etc., are also in use.
History
Georg Agricola (1494-1555) wrote the first systematic treatise about
mining and smelting works, De re
metallica libri XII, with an appendix Buch von den Lebewesen unter Tage (book of the creatures beneath the earth).
He covered subjects like wind energy, hydrodynamic power, melting cookers,
transport of ores, extraction of soda, sulfur and alum, and administrative issues. The book was
published in 1556.
James Hutton is often viewed as the first modern geologist. In 1785 he presented a paper entitled Theory of the Earth to the Royal Society of Edinburgh. In his paper, he explained
his theory that the Earth must be much older than had previously been supposed, in order to allow enough time for mountains to be
eroded, and for the sediment to form
new rocks at the bottom of the sea, which were then raised up to dry land.
Followers of Hutton were known as plutonists because they believed that some rocks were formed by vulcanism which is the deposition of lava from volcanoes, as opposed to the neptunists, who believed that
all rocks had settled out of a large ocean whose level gradually dropped over time.
William Smith (1769-1839) drew some of the
first geological maps and began the process of ordering rock strata (layers)
by examining the fossils contained in them.
Sir Charles Lyell first published his famous book,
Principles of Geology, in 1830 and continued to publish new revisions until he died
in 1875. He successfully promoted the doctrine of uniformitarianism. This theory states that slow geological processes occurred throughout the earth's
history, and are still occurring today. In contrast, catastrophism is the
theory that Earth's features formed in single, catastrophic events and remained unchanged thereafter. (Hutton believed in
uniformitarianism, but the idea was not widely accepted at the time.)
The theory of continental drift was proposed by Alfred Wegener in 1912 and by Arthur
Holmes, but wasn't broadly accepted until the 1960s when the theory of plate tectonics was developed.
See also: Timeline of geology
Fields
There are many different fields within the discipline of Geology, and it would be hard to list all of them. Some include,
however: geochemistry, hydrogeology (or geohydrology), petroleum geology, economic geology, soil science, climatology, biogeology, geodetics and geophysics.
Subdisciplines within geology proper include structural
geology, sedimentology and stratigraphy, mineralogy (study of minerals), petrology (study of rocks), geomorphology (study of landforms), seismology (also a
field in geophysics) and volcanology (the study of volcanoes).
There is also engineering geology, which supports civil
engineering, especially geotechnical
engineering, and geological engineering. The difference between geological engineering and engineering geology is
real: geological engineers are licensed as engineers, engineering geologists are licensed as geologists.
Regional Geology
National Geology
- Geology of the United
States of America
- Geology of
California
- Geology of the Grand Canyon
area
See also
External link
- James Hutton's Theory of the Earth
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