古磁場強度の変動は,メソプロテロゾイクの中核核化を示唆している
A J Biggin1, E J Piispa2, L J Pesonen3
1Department of Earth, Ocean and Ecological Sciences, University of Liverpool, Liverpool L69 7ZE, UK.
Nature
|October 10, 2015
まとめ
地球の内核は 約15億年前から 成長し始め 惑星の進化の重要な瞬間となりました この発見は古磁気データを基に 地球の熱史の単純なモデルを 支持しています
科学分野:
- 地理学
- 惑星科学
- 古磁気学
背景:
- 地球の内核は 液体鉄の固化によって成長します
- 内核核形成の時期の推定は,熱伝導率の値が異なるため,幅広く異なる (約50億〜20億年前).
- 内部核の形成は惑星の熱進化と地力学に影響を及ぼします
研究 の 目的:
- 地球の内核の核形成のタイミングを 精査する
- 地磁場強さの長期変動を調査する
- 地球の熱進化の特定のモデルを支持する証拠を提供するためです.
主な方法:
- 拡張されたプレカンブリア紀の古磁気強度データベースの分析
- 古磁気データを選択するための新しい信頼性基準の適用.
- 地磁場強度と地質学的時間尺度における変動性の検討.
主要な成果:
- この研究は,プレカンブリア時代の二極性に対する強度に基づく支持を提供します.
- 地磁気力の非常に長期的な変動の確固たる証拠が見つかりました.
- 平均的な磁場強度と変動性は10億年から15億年前に顕著に増加した.
結論:
- 観測された地磁場強度の変化は 内部核の形成が 10億年から15億年前に起こったことを強く示唆しています
- このタイミングは,控えめなコア熱伝導値をサポートします.
- この発見は地球における 単純な熱進化モデルと一致しています
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