The rotational stability of a convecting Earth: the Earth's figure and TPW over the last 100 Myr
The rotational stability of a convecting Earth: the Earth's figure and TPW over the last 100 Myr
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DOI：
10.1111/j.1365-246x.2011.05174.x
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发表时间：
2011-11-01
影响因子：
2.8
通讯作者：
Morrow, E.
中科院分区：
文献类型：
--
作者：
Chan, N. -H.;Mitrovica, J. X.;Morrow, E.
过去100年的古地磁记录表明，地球自转轴相对于地表地理(或真极移，TPW)的重新定位被限制在距离其当前位置不到6度的范围内。考虑到地球自转稳定性的正则理论通常预测地幔对流应该驱动极的更大位移，这种有限的TPW是意想不到的。我们认为，根据早期的工作，减弱的TPW是板块俯冲和深地幔超强羽流在非洲和太平洋下方上升导致的地球形状稳定、过度扁平的结果。特别是，我们表明，TPW记录与对流引起的对地球惯性张量的扰动是一致的，后者是过去100Myr中过剩扁平化的20%或更少；如果地球岩石圈在如此长的时间尺度上保持任何显著的弹性强度，这个上限将更高。这一推断的地球形状的稳定性对于我们理解深部地幔结构和地球的长期、全球尺度的演化具有重要的意义。
Palaeomagnetic records spanning the last 100 Myr indicate that the reorientation of the Earth's rotation axis relative to the surface geography (or true polar wander, TPW) has been confined to a range less than 6 degrees from its present location. This limited TPW is unexpected given that a canonical theory for the rotational stability of the Earth generally predicts that mantle convection should drive larger displacements of the pole. We argue, following earlier work, that the muted TPW is a consequence of the stable, excess flattening of the Earth's figure driven by plate subduction and deep mantle superplumes rising beneath Africa and the Pacific. In particular, we show that the TPW record is consistent with convection-induced perturbations to the Earth's inertia tensor of order 20 per cent or less of the excess flattening over the last 100 Myr; this upper bound will be higher if the Earth's lithosphere retains any significant elastic strength over such long timescales. This inferred stability of the Earth's figure has important implications for our understanding of deep mantle structure and the long-term, global-scale evolution of the Earth.