单词 | polarity epoch |
释义 | > as lemmaspolarity epoch polarity epoch n. Geology a long period of time (typically of the order of 100,000 to 10,000,000 years) over which the earth's magnetic field is predominantly of one polarity. ΚΠ 1963 Nature 15 June 1050/1 If the more recent polarity epochs are equal or nearly equal in length, the data of the present study strongly indicate that the epochs must be either ½ or 1 million years long. 1997 J. J. Lowe & M. J. C. Walker Reconstructing Quaternary Environments (ed. 2) 278 Polarity epochs..are interrupted by a large number of polarity reversals of shorter duration (104 to 105 years) which are termed polarity events. < as lemmas |
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