| 释义 | phreatic, a.|frɪˈætɪk|
[ad. F. phréatique (G. A. Daubrée Les Eaux Souterraines (1887) I. ii. 19), f. Gr. ϕρέαρ, ϕρέατ- well, cistern + -ic.]
1. Of, pertaining to, or designating water below the water-table, esp. that which is capable of movement.
1891R. J. Hinton Irrigation in U.S.: Progress Rep. for 1890 (U.S. 51st Congress, 2nd Sess. Senate Ex. Doc. No. 53) 42 At the point at which most of them leave the mountain ranges there commences an enormous phreatic absorption of the volume of flow that has descended from the summit above. 1892R. Hay Final Geol. Rep. (U.S. 52nd Congress, 1st Sess. Senate Ex. Doc. No. 41) iii. 8 Prof. Hill has given definitions of the technical words used by him, and to his list may be added the new word phreatic, which is a very convenient term for underground waters which can be, or which it is hoped may be, reached by wells or other sub-ground works. [Note] This word was first used in American hydro-geologic investigation by the Artesian and Underflow Office in 1890. 1892–314th Rep. U.S. Geol. Surv. ii. 16 ‘Phreatic water’. [Note] This term was coined by Hay, in the course of the recent artesian and underflow investigation.., as a convenient designation for ‘underground waters which can be, or which it is hoped may be, reached by wells or other subground works’. 1917Econ. Geol. XII. 494 Daubrée (1887, p. 19) invented ‘phreatic’ from a Greek expression for ‘well’... Originally..the word meant seepage water and particularly that below the water-table. It was so used by Hay (1892, p. 8) and McGee (1894, pp. 16, 42)... Suess (1909, p. 655) appears to have included in ‘phreatic water’ that of connate origin as well as seepage water... The writer believes that the history of the word and practical expediency should make ‘phreatic’ mean the infiltered waters which are bounded above by the water-table. 1954Times Lit. Suppl. 5 Feb. 93/2 Theories of their [sc. caves'] formation are classed as ‘vadose’ or ‘phreatic’ according as it is held that caves are formed above the water-table or below it. 1966Davis & DeWiest Hydrogeol. ii. 42 The zone of phreatic water merges at depth into a zone of dense rock with some water in pores, although the pores are not interconnected so that water will not migrate. 1973Nature 9 Nov. 77/2 After the solutional formation of a cavity beneath the water table, incision and reduction of local base level produced lowering of the phreatic surface. 1977A. Hallam Planet Earth 108 Where the top of the zone of saturation of an aquifer is a free-water surface it is known as the water table (or phreatic surface).
2. Of, pertaining to, or designating a volcanic explosion caused by the sudden heating and volatilization of underground water when it comes into contact with hot magma or rock.
1909H. B. C. & W. J. Sollas tr. Suess's Face of Earth IV. xvi. 568 Phreatic explosions. When juvenile hydrogen encounters an unlimited quantity of vadose water, we witness a spectacle such as was presented by Krakatoa in 1883... In this case the effect may have been due to phreatic water in the neighbourhood of the sea, but when phreatic water is confined in the fissures of a limestone formation, the explosion shatters the limestone. 1926R. A. Daly Our Mobile Earth iv. 158 Not all explosions are due to the pressure of magmatic gas... In the year 1888 the side of the Japanese cone, Bandai-San, was ripped out... The cavity, technically called a ‘phreatic caldera’, is about two miles long. Ibid., The 1924 explosion at Kilauea was of phreatic character. 1964New Scientist 5 Mar. 585/2 The co-existence and maintenance of such ‘phreatic’ activity (here ascribable to sea water suddenly flashed into steam by contact with hot lava in a vent) with the contrasting fire-fountains, characteristic of ‘Strombolian’ volcanic activity.., calls for somewhat unusual conditions. 1975Fielder & Wilson Volcanoes of Earth, Moon & Mars iv. 53/2 In a phreatic eruption, horizontal surges carry low density loads outwards from the eruptive centre. 1976P. Francis Volcanoes iv. 143 This steam sometimes blasts its way up to the surface through the lava, causing what is known as a phreatic explosion. |
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