溶岩流から推論された地磁場逆転の構造的および時間的要件
Brad S Singer1, Kenneth A Hoffman, Robert S Coe
1Department of Geology and Geophysics, University of Wisconsin, Madison, Wisconsin 53706, USA. bsinger@geology.wisc.edu
Nature
|April 1, 2005
まとめ
地球の磁場逆転は,地球外核のジオダイナモの変化と関連しています. 新しい年代測定法によると,不安定性は極性転換の1万8000年前から始まり,コアプロセスの理解に影響を及ぼしました.
科学分野:
- 地質物理学 地質物理学とは地質物理学です.
- 地球科学 地球科学 地球科学
- パレオマグネティズム (古磁気学) とは
背景:
- 地球の磁場逆転は,外核のジオダイナモプロセスによって引き起こされます.
- 逆転に先立つフィールド変化のタイミングと形態論を理解することは,コアとマントルの性質を制限するために重要です.
- 古代磁気記録はしばしば断片的であり,逆転プロセスのタイムラインを複雑にします.
研究 の 目的:
- 最新のマトゥヤマ-ブルンヘスの磁場逆転のタイムラインを精錬するために.
- 磁場極性変化の前およびその間におけるジオダイナモ過程を調査する.
- コアダイナミクス,コア内部の影響,および逆転の開始の間の関係を評価する.
主な方法:
- タヒチ,チリ,ラ・パルマ,マウイの火山岩の40Ar/39Ar年代測定を用いた.
- Matuyama-Brunhes逆転の放射線年代と天文年代を比較した.
- 移行フィールド状態と強度の変化を特定するために,古磁気データを分析しました.
主要な成果:
- 795 ± 7 kyrの日付のタヒチからの溶岩は,受け入れられた逆転年齢よりも古い.
- マウイとラ・パルマ (776 ± 2 キル) の移行ラバは,天文学的逆転年齢と一致しています.
- 古い溶岩は,極性スイッチを約18,000年前に先行した最初のジオダイナモの不安定性を記録している可能性が高い.
結論:
- ジオダイナモの不安定性の発生は,実際の磁気極性逆転に先行する.
- 磁気流が内核から逃れ,安定効果を弱めるには,かなりの時間がかかります.
- これらの発見は,地球の磁場逆転を制御する複雑なプロセスに関する新しい洞察を提供します.
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