Heterogeneity and time dependence in 3D spherical mantle convection models with continental drift
Heterogeneity and time dependence in 3D spherical mantle convection models with continental drift
复制标题
DOI：
10.1016/j.epsl.2005.01.041
复制
发表时间：
2005-04
影响因子：
5.3
通讯作者：
B. Phillips;H. Bunge
中科院分区：
文献类型：
--
作者：
B. Phillips;H. Bunge
大陆之间的反馈和通过热覆盖的大规模地幔流动一直被推测为大陆漂移和威尔逊旋回的机制。古地磁学提供了大陆在1亿~ 2亿年时间尺度上大规模位移（约10，000 km）的证据，相当于整个地幔对流的内在翻转。在这里，我们在充满活力的三维球形对流模型中模拟大陆运动，重点是大陆大小，地幔加热模式和下地幔粘度的强烈增加的影响。覆盖地球表面30%，10%和3%的大陆（代表前超大陆盘古大陆，今天的亚洲和南极洲，分别）被引入到简单的端元地幔对流模型，其特征是纯核心或内部加热，均匀或分层地幔粘度。超大陆促进温度异常的最大规模（球谐度1和2），主要是通过组织的长波对流平面形状固有的模型与高粘度下地幔。底部加热可以通过在大陆下方聚集羽流来促进长波不均匀性。然而，在等粘模型中，无论加热模式如何，远离大陆的小尺度结构仍然存在。超大陆对长波长不均匀性的反应是沿着速度在10亿年时间尺度上变化的大圆路径运动。较小的大陆无法促进长波长结构，由此产生的运动受到时间尺度为1亿年的速度爆发的控制。大陆板块的速度比海洋板块的速度大约小1.23倍，这一观测结果可能有助于解释所观测到的主要大陆板块和海洋板块速度的差异。
Feedback between continents and large-scale mantle flow through thermal blanketing has long been surmised as a mechanism for continental drift and Wilson cycles. Paleomagnetism provides evidence for extensive continental displacements (∼ 10,000 km) on time scales of 100–200 million years, comparable to an intrinsic overturn in whole mantle convection. Here we model continental motions in vigorous 3D spherical convection models, focusing on the effects of continent size, mantle heating mode, and a strong increase in lower mantle viscosity. Continents covering 30%, 10%, and 3% of Earth's surface (representative of the former supercontinent Pangea, present-day Asia, and Antarctica, respectively) are introduced into simple end member mantle convection models characterized by pure core or internal heating, and uniform or layered mantle viscosity. Supercontinents promote temperature anomalies on the largest scales (spherical harmonic degrees 1 and 2), primarily through the organization of the long-wavelength convective planform inherent in models with a high-viscosity lower mantle. Bottom heating can promote long-wavelength heterogeneity by clustering plumes beneath the continent. However, in isoviscous models small-scale structure persists away from the continent regardless of the heating mode. Supercontinents respond to long-wavelength heterogeneity by following great circle paths with variations in velocity on time scales of 1 billion years. Smaller continents are unable to promote long-wavelength structure, and the resulting motions are governed by bursts in velocity on time scales of the order of 100 million years. Continental velocities are roughly a factor of ∼ 3 smaller than those in oceanic regions, an observation that may help explain the observed difference in the speed of predominantly continental or oceanic plates.