Science. 1987 Sep 4;237(4819):1140-7. doi: 10.1126/science.237.4819.1140.
True polar wander, the shifting of the entire mantle relative to the earth's spin axis, has been reanalyzed. Over the last 200 million years, true polar wander has been fast (approximately 5 centimeters per year) most of the time, except for a remarkable standstill from 170 to 110 million years ago. This standstill correlates with a decrease in the reversal frequency of the geomagnetic field and episodes of continental breakup. Conversely, true polar wander is high when reversal frequency increases. It is proposed that intermittent convection modulates the thickness of a thermal boundary layer at the base of the mantle and consequently the core-to-mantle heat flux. Emission of hot thermals from the boundary layer leads to increases in mantle convection and true polar wander. In conjunction, cold thermals released from a boundary layer at the top of the liquid core eventually lead to reversals. Changes in the locations of subduction zones may also affect true polar wander. Exceptional volcanism and mass extinctions at the Cretaceous-Tertiary and Permo-Triassic boundaries may be related to thermals released after two unusually long periods with no magnetic reversals. These environmental catastrophes may therefore be a consequence of thermal and chemical couplings in the earth's multilayer heat engine rather than have an extraterrestrial cause.
真正的极移，即整个地幔相对于地球自转轴的移动，已经被重新分析。在过去的 2 亿年中，真正的极移大部分时间都很快（大约每年 5 厘米），除了在 1.7 亿至 1.1 亿年前的一段显著的停顿。这种停顿与地磁场反转频率的降低和大陆分裂事件相关。相反，当反转频率增加时，真正的极移就会很高。有人提出，间歇性对流会调节地幔底部热边界层的厚度，从而影响地核-地幔热通量。边界层中热流的释放会导致地幔对流和真正的极移增加。同时，从液态核心顶部边界层释放的冷流最终会导致反转。俯冲带位置的变化也可能影响真正的极移。白垩纪-第三纪和二叠纪-三叠纪边界的异常火山活动和大规模灭绝可能与两次异常长的无磁场反转期后释放的热流有关。因此，这些环境灾难可能是地球多层热机中的热和化学耦合的结果，而不是外星原因造成的。
