geolgy

[Fr. géologie, from Gr. geō, for geios = belonging to the earth; ge = the earth, and logos a discourse.] 1. The science which investigates the bygone his tory of the earth with the view of accounting for its present condition. It inquires into the succe ive changes which have taken place in the organic and inorganic kingdoms of nature, seeks out the causes of these changes, and traces the influence which they have exerted in modifying the surface and the external appearance of the earth. It is the province of physical and political geography to describe what the earth now is, geology attempts to furnish the reason why. (1) Hist of Geology : Though it is only during the present century that geology has started up into the vigor of manhood, yet its birth took place ages ago. Isolated geological observations or hypotheses occur abundantly in ancient literature. "As for the earth, out of it cometh bread; and under it is turned up as it were fire" (Job xxviii. 5); an anticipation of the Huttonian hypothesis. Egypt, according to Hero dot us, is the gift of the Nile, that is, the river brought down the silt which constitutes the fertile soil of the Delta and other parts of Lower Egypt. Though there is a mixture of erroneous hypotheses in the statements attributed to Pythag. or as, in Ovid's Metamorphoses , bk. xv., other parts would have done no discredit to Sir Charles Lyell. Pythagoras himself lived, it is thought, about 580 B. C., but the views handed down by Ovid were probably those of Pythagoreans in the August an age rather than those of Pythagoras. The best geologist of antiquity was the geographer Strabo, who lived in the first century A. D. For the long controversy regarding the nature of fo ils, and if they were organic when they were entombed, see Fo il. Modern geology began with Werner, who was a Profe or in the School of Mines, at Freiberg, in 1995 2. Lower Silurian: (3) Trenton, (2) Chazy, (1) Calcifer 1. Cam brian. SUB-DIVISIONS. Saxony, in 1775. He believed that a series of uni- versal formations had been deposited in succe ion ous. from a chaotic fluid. Basalt was supposed to have had the same origin, but to this view various conti- Eozoic (dawn of life), Azoic (lifele ). nental observers were opposed. Hutton published in 1788 his Theory of the Earth , developed in a sep- arate work in 1795. He a umed no causes but those now existing. He showed that geology and cosmogony were different. "In the economy of the world," he said, "he could find no trace of a begin ning, no prospect of an end." He held basalt, granite, ., to be of igneous origin. The Wesner- ians were called Neptunists, their opponents Vulcan- ists. In 1798 Cuvier published his O emens Fo iles, which gave a great impulse to paleontology. [(2).] (2) The forces or causes in operation: After in quirers had outgrown the belief in fo ils produced by the plastic power of nature or all entombed simultaneously by the Noachian deluge, the belief was entertained that there had been a series of creations and catastrophes, the latter causing the universal destruction of all preexisting species. The belief was also entertained that some external causes, say the forces producing earthquake and volcanic action, were more potent in former times than now. This Prof. Huxley calls Catastrophism, which he defines to be any form of geological spec- ulation which, in order to account for the phenom- ena, supposes the operation of forces different in their nature or immeasurably different in power from those which are at present in action in the universe. Sir Roderick Murchison was of this school with many continental geologists. 9. Quaternary: Pleistocene; 8. Tertiary : English Crag, Upper Mola e, Rupelian and Tongrian of Belgium; 7. Cretaceous: Upper Chalk, Lower Chalk, Chalk Marl, Gault, Neocomian, Lower Greensand; 6. Jura- Trias : Wealden, Purbeck, Portland, Kim me ridge, Oxford Oölites, Lower or Bath Oölite, Lower Lias, Marlstone, Upper Lias, Kö en beds, Dachstein beds; Alpine Trias, in Keuper, Muschelkalk, Bunter-Sand stein; 5. Carboniferous: Magnesian Limestone, Lower Red Sand The doctrine of the third school of geologists is called by Prof. Huxley Evolutionism; it accepts nearly the whole of Uniformitarianism, except the part referring to the development of organic life. In his later years Sir Chas. Lyell became an evolutionist. [DARWIN ISM, EVOLUTION, .] (3) Geologic time : Both the uniformitarian and the evolutionist believe that they may draw to any extent on what may be called the bank of time, which will be found "ready to discount any quantity of hypothetical paper." Sir Wm. Thomson holds that any such drafts must be limited "within some such period of time millions of years;" and another natural philosopher con siders the time at call only about sixty millions of years. Prof. Huxley believes the nece ity for these limitations is not proved, though perhaps one, two, or three hundred millions of years might be enough to account for geological phenomena. With regard to the subdivision of the time, long or short, at the geologist's command, the sedimen tary strata having been laid down by water, the relative thickne of each stratum will measure the proportion of geologic time required for its deposition. IMG:content-0421.png:[blocks in formation] 9. Quaternary or Post Tertiary: (3) Recent, (2) Cham plain, (1) Glacial. 8. Tertiary Era : (4) Pliocene, (3) Miocene, (2) Oligocene, (1) Eocene. 7. Cretaceous Era : (4) Laramie, (3) Colorado, (2) Dakota, (1) Lower. 6. Jura-Trias: (b) Jura ic: (3) Purbeck, (2) Oülite (1) Lias. (a) Tria ic: (4) Rhætic, (3) Upper, (2) Middle, (1) Lower. 5. Carboniferous Era : (3) Permian, (2) Carboniferous (1) Sub-carboniferous.: 4. Devonian Era: (5) Cat skill and Chemung, (4) Port age, (3) Hamilton, (2) Corniferous, (1) Oriskany. 3. Upper Silurian : (3) Lower Helderberg, (2) Onondaga, (1) Niagara. stone, or Rothliegendes, Upper Coal Measures, Lower Coal Measures, Millstone Grit, Lower Carboniferous, Mountain Limestone; 4. Devonían: Old Red Sandstone Cat skill Red Sandstone, Chemung, Portage, Gene see Slate, Hamilton beds, Mar cell us Shale, Upper Helderberg, Schoharie, Grit, Oriskany Sandstone; 3. Upper Silurian: Lower Helderberg, Onondaga Salt Group, Salina beds, Water Lime, Niagara Group, Wenlock Group, Clinton Group, Medina Sandstone (Upper Llandovery); 2. Lower Silurian : Hudson River beds, Cincinnati Group, Lower Llandovery, Utica Shales, Trenton Limestone, Chazy Limestone, Calciferous Sand rock, Magnesian Limestone, Lower, Middle and Upper Cam brian; 1. Archœan: Lauren tian, Huronian. Caradoc Limestone, Black River Limestone, (5) Other rocks : For these, see IGNEOUS ROCKS, VOLCANIC Rocks. (6) Fo ils : For these, see FOSSILS; see also PALEONTOLOGY. (7) Applied geology: Geology applied to industrial or other practical purposes; as, for instance, to mining, drainage, railway tunneling, .