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The Brunhes–Matuyama reversal, named after Bernard Brunhes and Motonori Matuyama, was a geologic event, approximately 781,000 years ago, when the Earth's magnetic field last underwent reversal.〔(【引用サイトリンク】url=http://www.stratigraphy.org/upload/QuaternaryChart1.JPG )〕 Opinions vary as to the abruptness of the reversal: it may have occurred over several thousand years, or much more quickly, perhaps within a human lifetime. The apparent duration at any particular location varied from 1,200 to 10,000 years depending on geomagnetic latitude and local effects of non-dipole components of the Earth's field during the transition.〔 The Brunhes–Matuyama reversal is a Global Boundary Stratotype Section and Point (GBSSP), selected by the International Commission on Stratigraphy as a marker for the beginning of the Middle Pleistocene, also known as the Ionian Stage.〔(【引用サイトリンク】url=http://www.stratigraphy.org/GSSP/index.html )〕 It is useful in dating ocean sediment cores and subaerially erupted volcanics. ==See also== *Geomagnetic reversal * Jaramillo reversal 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Brunhes–Matuyama reversal」の詳細全文を読む スポンサード リンク
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