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magma|ˈmægmə|
[a. L. magma (sense 1), Gr. µάγµα, f. root of µάσσειν to knead.]
†1. The dregs that remain from a semi-liquid substance after the more liquid part has been removed by pressure or evaporation. Obs.
c1420Pallad. on Husb. xi. 351 Taak aloen & mirre & magma with Saffron [L. crocomagma lees of saffron], of yche yliche. a1648Digby Closet Open. (1677) 18 You may squeze out the clear juyce and hang the Magma in a bag in the bung. 1694Salmon Bate's Dispens. (1713) 38/2 By another Distillation, reduce the Magma at bottom, to the Consistency of Honey. 1730Stack in Phil. Trans. XXXVI. 271 The Eggs..resemble a Magma of a brown Colour. 1737Bracken Farriery Impr. (1756) I. 310 Apply the Magma (or Herbs after they are squeezed out of the Liquor) to the Wound. 1856Mayne Expos. Lex., Magma,..a squeezed mass of a certain consistence.
2. ‘Any crude mixture of mineral or organic matters, in a thin pasty state’ (Ure Dict. Arts 1839).
1681tr. Willis' Rem. Med. Wks. Vocab., Magma, the blended dross and fæces of several metals, as also of chymical extractions. 1782Kirwan in Phil. Trans. LXXIII. 17 [They] afford no crystals, but only a magma or mother liquor. 1806Hatchett ibid. XCVI. 111 It formed with sulphuric acid a thick black magma. 1838T. Thomson Chem. Org. Bodies 688 A concentrated solution of potash forms with bird-lime a whitish magma, which becomes brown by evaporation. 1854J. Scoffern in Orr's Circ. Sci., Chem. 24 A magma of dark-coloured sugar. 1875H. C. Wood Therap. (1879) 93 It..should be so moist as to constitute a magma. 1894Huxley Wks. IX. 8 Our earth may once have formed part of a nebulous cosmic magma.
3. Geol.
a. One of two or more supposed strata of fluid or semi-fluid matter lying beneath the solid crust of the earth. In mod. use: A hot, fluid or semi-fluid material beneath the earth's crust from which igneous rocks are believed to be formed by cooling and solidification and which erupts as lava.
b. The amorphous basis of certain porphyritic rocks.
1865Haughton Man. Geol. 3 According to Durocher..the first and second layers of the globe are composed of totally different materials. The outer layer, which he calls the Acid Magma, corresponds with the granites; and the inner or second layer, which he calls the Basic Magma, corresponds with the trap rocks and the greenstones. 1869Phillips Vesuv. xii. 336 Whether these rocks..constitute practically a solid basis, or float in a magma of slow fluidity. 1874Dawkins in Ess. Owen's Coll. Manchester V. 148 Two distinct layers or magmas beneath the stratified rocks. 1882Geikie Text-bk. Geol. ii. ii. iii. 87 Many crystalline rocks consist..of a magma or paste, in which the crystalline particles are..embedded. 1897― Anc. Volcanoes Gt. Brit. I. 12 There will thus be a constant pressure of the molten magma into the roots of volcanoes. 1944A. Holmes Princ. Physical Geol. iii. 28 A volcano is essentially a rift or vent through which magma (molten rock material highly charged with gases) from the depths is erupted at the surface. 1955Sci. News Let. 19 Mar. 187/3 The liquefied material forms a fluid mass, called magma, that is lighter than the overlying rocks and tends to rise at an opening. Magma is called lava when it reaches the earth's surface. 1971I. G. Gass et al. Understanding Earth xxi. 310/2 At the close of volcanism, the magma in these chambers will also solidify to coarse-grained rocks having the same composition as the lavas which previously were being erupted.
4. Pharmacy. An ointment or confection of a softish consistence. (Syd. Soc. Lex. 1889.)
1855Dunglison Med. Lex. (ed. 12), Magma..also, a salve of a certain consistence.
5. fig.
1928R. A. S. Macalister Archæol. of Ireland iv. 219 A conglomerate of lazy abbreviations..studded in a repulsive magma of exotic gibberish. 1933H. G. Wells Shape of Things to Come iii. §1. 261 The need for a planned ‘renucleation’ in the social magma that arose out of this dissolution.
6. attrib., as (sense 3) magma reservoir.
1909A. Harker Nat. Hist. Igneous Rocks ii. 36 At the depth at which we suppose a large magma-reservoir to be situated the conditions would be quite different. 1971I. G. Gass et al. Understanding Earth xxi. 303/1 Because these volcanoes are large and their volcanic history is long, the magma reservoirs beneath them..have fractionated, giving rise to diversified lava assemblages.
Hence magˈmatic a., of or pertaining to the magma (sense 3).
1890in Cent. Dict. 1903Geikie Text-bk. Geol. (ed. 4) II. 808 (heading) Magmatic ores. 1910Encycl. Brit. III. 513/2 The modifications of the granite are ascribed to magmatic segregation (chemical and physical processes which occasioned diffusion of certain components towards the cooling surfaces). 1933Geogr. Jrnl. LXXXI. 332 Magmatic movement, however caused, has been a factor in the formation of the Rift Valleys. 1957G. E. Hutchinson Treat. Limnol. I. i. 33 Intermittent volcanic activity..repeatedly drew off material from the magmatic reservoir. 1971I. G. Gass et al. Understanding Earth i. 24/1 Quartz and nepheline if brought into contact at magmatic temperatures react to give albite.
Add: magˈmatically adv., as regards magma; from or by means of magma.
1947Jrnl. Geol. LV. 330/1 A group of basic intrusions in the Baker quadrangle are all believed to be magmatically related and hence of a single intrusive cycle. 1977A. Hallam Planet Earth 112 Magmatically derived water, meteoric water..sea water and water contained in deep sedimentary formations have all been found in the cores of porphyry copper deposits. 1988Nature 28 Apr. 779/1 A cause of controversy is the hypothesis that this accretionary plate boundary is segmented into adjacent but separate spreading cells, each driven magmatically but possibly by different plumes. |