A geologic period is a subdivision of geologic time that divides an era into smaller timeframes. The equivalent term used to demarcate rock layers and the fossil record is the system; thus the rocks of the Devonian System were laid down during the Devonian Period. While paleontologists often refer to faunal stages rather than geologic periods, they are often used in popular presentations of paleontology. Such references include the book and movieJurassic Park. The table and timeline of geologic periods presented here is in accordance with the dates and nomenclature proposed by the International Commission on Stratigraphy. ... A geologic era is a subdivision of geologic time that is a separate classification that divides the Phanerozoic Eon into three parts timeframes. ... Rock Layers are formed by constant build up of sediment. ... It has been suggested that this article or section be merged into Fossil. ... Faunal stages are a subdivision of geologic time used primarily by paleontologists who study fossils rather than by geologists who study rock formations. ... Paleontology, palaeontology or palæontology (see spelling differences) is the study of the history and development of life on Earth, including that of ancient plants and animals, based on the fossil record (evidence of their prehistoric existence as typically preserved in sedimentary rocks). ... A chained book in the Bodleian Library at Oxford University A Chinese bamboo book, in a collection at the University of California, Riverside. ... Film is a term that encompasses individual motion pictures, the field of film as an art form, and the motion picture industry. ... Jurassic Park is a novel written by Michael Crichton that was published in 1990. ...
As illustrated in the article on the geologic time scale, most periods are subdivided into smaller units called epochs. In 2004 the International Union of Geological Sciences (I.U.G.S.) recognized the Ediacaran period of the Neoproterozoic era, the first such newly-designated period in 130 years. // For other uses, see time scale. ... Look up epoch in Wiktionary, the free dictionary. ... IUGS logo The International Union of Geological Sciences (IUGS) is an international non-governmental organization devoted to international cooperation in the field of geology. ... The Ediacaran Period is the last geological period of the Neoproterozoic Era, just before the Cambrian. ... The Neoproterozoic is the geological era from 1000 Ma to 542 Ma (million years ago). ...
Some Geologists still designate a third period, or "sub-era", of the Cenozoic Era called the Quaternary, comprising the last two epochs of the Neogene Period and extending up to the present.
The periods are generally named after the regions where rocks of the period in question are well exposed; for example, the Permianperiod is named after the European province of Perm in Russia.
This major branch of geology is geared to the analysis, exploration, and exploitation of geological materials of use to humans, such as fuels, metals and non-metallic minerals, water, and geothermal energy.
The scope of environmental geology is exceptionally broad, comprising as it does physical sciences such as geochemistry and hydrology, as well as biological and social sciences, and engineering.
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