Collaborative Research: The Asthenosphere and Mantle Dynamics

地球上发生的大部分变化可以追溯到两种能量来源之一：1)来自太阳的能量和2)来自地球内部的能量。内部能量如何塑造地球表面直接关系到对板块构造动力学的理解。板块构造学与量子力学和相对论并称为20世纪三大科学革命之一。作为一种理论，它仍然是一种运动学理论，因为它描述了地球表面板块的运动，但没有直接将运动与驱动运动的力联系起来。在地质和地球物理学界，将板块构造理论从运动学理论扩展到动力学理论一直是一个巨大的挑战。从板块构造作为一种运动学理论开始，人们就怀疑板块构造的动力学与板块下方一个低粘度带——软流层的存在有关。映射，量化，并寻求将概念理解的几个因素，这些因素与这种长期怀疑的联系是这项工作的主题。更具体地说，在接下来的一年周期中，该团队将：A)测试软流圈结构的变化可以驱动最近在地球上发现的5000 -1亿年前发生的板块运动的快速变化的假设；B)探索板块构造与地表储层和地球深层内部之间挥发物循环之间的相互作用（例如，深水循环可以通过其在岩石融化中的作用影响软流圈的性质）。研究人员将探索低粘度软流圈对地幔动力学的影响。数值地幔对流实验将用于绘制低粘度软流圈和板块边界破坏对维持板块-构造模式的地幔对流的综合影响。一个具体的目标将是确定允许板块运动快速变化的条件，就像最近对地球白垩纪的推断一样。数值工作将被理论尺度分析所加强。该分析将深入了解与板块边缘、软流层和大块地幔耗散相关的板块运动阻力之间的能量平衡。这将允许pi将动态建模与瞬时流动研究联系起来，从而隔离板块过程和整体地幔之间的耗散平衡。这种联系将给他们的结果和预测带来额外的观测限制。该分析还将扩展到模拟地球内部的深层挥发性循环（水和碳）以及地质时期地球表面到内部的挥发性交换。相对于软流圈在维持板块构造方面的作用，这一研究引入的关键反馈来自挥发物影响上地幔融化的能力，这可以显著改变软流圈的结构。

The majority of changes that occur on our planet can be tracked back to one of two energy sources: 1) Energy from the sun and 2) Energy from the Earth's interior. How interior energy shapes the Earth's surface links directly to understanding the dynamics of plate tectonics. Plate tectonics stands as one of the three major scientific revolutions of the 20th century, along with quantum mechanics and relativity. As a theory it remains a kinematic one in that it describes the motion of plates at the Earth's surface but does not connect the motions directly to the forces that drive the motion. Extending plate tectonics theory from a kinematic one to a dynamic one has been a something of a grand challenge in the geological and geophysical communities. From the inception of plate tectonics as a kinematic theory, it has been suspected that the dynamics of plate tectonics is connected to the existence of a low viscosity zone below plates - the asthenosphere. Mapping, quantifying, and seeking to bring conceptual understanding to several of the factors that tie into this long suspected connection is the theme of this work. More specifically, over the next one year cycle, the team will: A) Test the hypothesis that changes in asthenosphere structure can drive rapid changes in plate motion of the type recently identified to have occurred on the Earth 50-100 Million years ago and B) Explore the interaction between plate tectonics and the cycling of volatiles between surface reservoirs and the Earth's deep interior (e.g., deep water cycling can effect the nature of the asthenosphere through its role on rock melting).The investigators will explore the effects of a low viscosity asthenosphere on mantle dynamics. Numerical mantle convection experiments will be used to map the combined effects of a low-viscosity asthenosphere and plate boundary failure on maintaining a plate-tectonic mode of mantle convection. A specific goal will be to identify conditions that allow for rapid changes in plate motions, as have recently been inferred for the Earth's Cretaceous. Numerical work will be augmented with theoretical scaling analysis. The analysis will provide insight into energetic balances between the resistance to plate motion associated with dissipation at plate margins, within the asthenosphere, and in the bulk mantle. This will allow the PIs to link dynamic modeling to instantaneous flow studies that isolate the balance of dissipation between plate processes and the bulk mantle. That link will bring added observational constraints to bear on their results and predictions. The analysis will also be extended to model deep volatile cycling (water and carbon) within the Earth and volatile exchange from the surface to the interior of our planet over geologic time. The key feedback this introduces, relative to the role of the asthenosphere on maintaining plate tectonics, comes from the ability of volatiles to effect melting in the upper mantle, which can significantly alter the structure of the asthenosphere.