CAREER: Investigating fast motion of the Indian plate with geodynamic models

板块构造学是一种解释大陆漂移的理论，它解释说，大陆漂移是地球外表面分裂成板块的结果，这些板块在地质时间内相互移动和滑动。板块中最年轻的部分是由世界上火山山脊的海底扩张产生的--S大洋，它取代了板块中较老的部分，这些板块通过一种被称为俯冲的过程重新循环回到地球内部。当这一理论在20世纪60年代的S时期形成时，它是一场与生物学进化论和物理学量子力学相媲美的地球科学革命，因为它为统一理解地球的构造作用和火山作用提供了一个概念框架。然而，这一最初的理论仅仅是一套描述板块运动运动学的规则。以下问题突显了我们缺乏更深层次的理解：板块构造是如何工作的？板块构造学什么时候开始的？为什么地球会有板块构造？这些问题的答案对于更多地了解地球的演化--S的大陆、海洋、大气，甚至生命本身--至关重要。这个项目将研究印度板块在7000万至4500万年前(Ma)异常快速运动的动力学原因，当时印度板块漂移的速度比典型俯冲板块的速度快1.5-2倍。通过试图理解如此异常快的板块速度，我们对板块构造如何工作以及地球如何演化的知识将会得到改善。该项目的一个重要方面是它的创新教育部分，这是一个全国性的地球动力学REU试点方案，旨在加强地球动力学领域高素质的准博士学生的申请库，并增加代表不足群体的成员的参与。该项目每年夏天将支持四名本科生研究人员，其中一名由SIO的Pi-Stegman主持，另外三名由全国各地的参与机构主持。所有REU参与者将致力于一个吸引人的、设计良好的项目，直接推动整个项目的研究和教育目标，包括他们在夏季的工作为其贡献的后续出版物的作者。这一倡议通过加强全国计算地球动力学小组之间的联系为社区建设提供了一个框架，通过提高成功吸引和招收高素质博士生的能力实现了互惠互利。从67 Ma开始，印度板块达到了超过16厘米/年的峰值速度，几乎是俯冲板块典型速度(&amp；#8764；6-8厘米/年)的两倍，然后以超过10-12厘米/年的速度保持到52 Ma。这一引人注目的事件的开始恰逢德干烟柱头部的到来，人们认为它产生了一场被称为德干圈闭的巨大火山喷发。该项目将建立在最近发现的一种新的板块推动力--烟柱推力(Cande和Stegman，2011)的基础上，除了作用于该系统的板块拉力和脊推力之外，该推动力可能还可以解释印度的快速运动。目前的观察表明，地幔热柱既影响板块运动，也影响板块边界形成的位置，但如何以及为什么形成板块边界的潜在物理过程尚不清楚。地幔对流的数值模型将被用来系统地研究印度的运动，并将受到各种地球物理和地质观测的限制。此外，还将利用地球动力学模型定量研究羽流推力作用的物理机制。最后，该项目将研究使垂直头能够在短时间间隔(5-10Myr)内促进板块边界重组的物理机制，塞舌尔微板块在70-60 Ma之间的构造历史表明，这可以用来增加对隆起和水平力平衡演化的时空约束。该项目的成果将以一种尚未实现的方式提高对板块构造进行建模的能力：作为一个具有自我一致演变的板块驱动力的全动态、依赖时间的3D系统。

Plate tectonics is the theory that explains continental drift as the result of Earth's outer surface being broken into plates that move and slide past each other over geological time. The youngest portion of the plates are generated by seafloor spreading at volcanic ridges in the world?s oceans which replaces the older portions of the plates that get recycled back into the Earth's interior through a process known as subduction. When this theory was formulated during the 1960's, it was a scientific revolution for Earth sciences on par with the theory of evolution for biology and quantum mechanics for physics, as it provides a conceptual framework for understanding Earth's tectonism and volcanism in a unifying way. However, this initial theory was merely a descriptive set of rules for the kinematics of plate motion. Our lack of a deeper understanding is highlighted by questions such as: How does plate tectonics work? When did plate tectonics begin? And Why does Earth have plate tectonics? The answers to these questions are central for learning more about the evolution of Earth?s continents, oceans, atmosphere, and even life itself. This project will investigate the dynamical causes for unusually rapid motion of the Indian plate observed between 70 and 45 Million years ago (Ma), when the Indian plate was recorded to have drifted 1.5-2 times faster than the typical speed of subducting plates. By attempting to understand such an anomalously fast plate speed, our knowledge of how plate tectonics works, and how Earth has evolved, will be improved. A significant aspect of this project is its innovative educational component, a pilot-scale nationwide REU program in geodynamics aimed to strengthen the applicant pool of highly qualified prospective PhD students within geodynamics and increase participation from members of underrepresented groups. This program will support four undergraduate researchers each summer with one hosted by PI-Stegman at SIO and three others hosted by participating institutions across the nation. All REU participants will work on an engaging, well-designed project that directly advances the research and educational objectives of the overall project,including authorship of subsequent publications to which their work over the summer contributed. This initiative provides a framework for community building by strengthening ties between computational geodynamics groups nationally, by offering the mutual benefit of an enhanced ability to successfully attract and recruit highly qualified PhD students.Beginning at 67 Ma, the Indian plate achieved peak velocities in excess of 16 cm/yr, or nearly double the typical velocity of subducting plates (∼6-8 cm/yr), and then sustained speeds in excess 10-12 cm/yr until 52 Ma. The start of this remarkable event is coincident with the arrival of the Deccan plume head that is thought to have produced an enormous volcanic eruption known as the Deccan traps. This project will build upon the recent discovery of a new plate driving force, the plume-push force (Cande and Stegman, 2011), which may play a role in explaining the fast motion of India in addition to slab-pull and ridge-push forces acting on the system. Current observations suggest mantle plumes influence both plate motions as well as where plate boundaries form, but the underlying physical process for how and why is not yet known. Numerical models of mantle convection will be employed to systematically investigate the motion of India, and will be constrained by a diverse suite of geophysical and geological observations. Furthermore, the physical mechanism through which the plume-push force acts will be quantitatively investigated with geodynamic models. Lastly, this project will investigate the physical mechanism that allows a plumehead to facilitate plate boundary reorganizations over short intervals of time (5-10 Myr), as indicated by the tectonic history of the Seychelles microplate between 70-60 Ma which can be used to add spatial-temporal constraints on the uplift and horizontal force-balance evolution. The outcomes of this project will advance the capability to model plate tectonics in a way yet to be achieved: as a fully-dynamic, time-dependent 3D system with self-consistently evolving plate driving forces.