| 释义 |
unˈdation
[ad. L. type *undātio, f. L. undāre to rise in waves. Cf. OF. undation, -acion.]
A waving; an undulation. Obs. rare exc. in b.
1656Blount Glossogr., Undation, a flowing or rising of waves. 1668Culpepper & Cole Barthol. Anat. ii. vi. 101 A certain Undation or waving towards one side according to the carriage of the right Ventricle.
b. undation theory Geol. [tr. Du. undatietheorie (1932)], the theory that selective internal heating of the earth's mantle causes large wave-like folds to appear in the crust.
1932R. W. van Bemmelen in Natuurk. Tijdschr. Nederlandsch. Indië XCII. 93 The geologic history of the western part of the Sunda arc has been examined according to the Undation Theory. 1950P. H. Kuenen Marine Geol. ii. 146 In his undation theory, van Bemmelen (1939) postulates a primary salsima layer formerly enveloping the whole earth and now forming the floor of the oceans. 1975Nature 3 Apr. 386/1 The..hypothesis bears some resemblance to the minority view of Van Bemmelen..and others, whose ‘undation theory’ proposes that selective high radioactive heating in the mantle produces warping of the overlying crust followed by lateral spreading under gravity. |