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

职业：利用地球动力学模型研究印度板块的快速运动

• 批准号: 1255040
• 负责人: Dave Stegman
• 金额: $ 72.5万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-07-01 至 2019-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1255040&HistoricalAwards=false
• 关键词: CAREER; Investigating; fast; motion; Indian

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.

板块构造学理论解释了大陆漂移是地球外表面破碎成板块在地质时期相互移动和滑过的结果。板块中最年轻的部分是由世界海洋火山脊处的海底扩张产生的，它取代了板块中较老的部分，这些较老的部分通过称为俯冲的过程再循环回地球内部。当这一理论在 20 世纪 60 年代提出时，它是地球科学的一场科学革命，与生物学的进化论和物理学的量子力学一样，因为它为以统一的方式理解地球的构造运动和火山活动提供了概念框架。然而，这个最初的理论仅仅是板块运动运动学的一组描述性规则。诸如以下问题凸显了我们缺乏更深入的理解：板块构造如何运作？板块构造何时开始？为什么地球有板块构造？这些问题的答案对于更多地了解地球大陆、海洋、大气甚至生命本身的演化至关重要。该项目将调查 70 至 4500 万年前（Ma）期间观察到的印度板块异常快速运动的动力学原因，当时印度板块的漂移速度被记录为俯冲板块典型速度的 1.5-2 倍。通过尝试了解如此异常快的板块速度，我们对板块构造如何运作以及地球如何演化的了解将会得到提高。 该项目的一个重要方面是其创新的教育组成部分，这是一个全国性 REU 地球动力学试点项目，旨在加强地球动力学领域高素质未来博士生的申请人库，并增加代表性不足群体成员的参与。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 参与者都将致力于一个引人入胜、精心设计的项目，该项目将直接推进整个项目的研究和教育目标，包括他们在夏季的工作所贡献的后续出版物的作者身份。该倡议通过加强全国计算地球动力学团体之间的联系，通过提供成功吸引和招募高素质博士生的增强能力的互惠互利，为社区建设提供了一个框架。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的两倍（∼6-8 厘米/年），然后 持续速度超过每年 10-12 厘米，直到 52 Ma。这一非凡事件的开始与德干羽流头的到来同时发生，人们认为德干羽流头产生了被称为德干火山圈的巨大火山喷发。该项目将建立在最近发现的一种新的板块驱动力——羽流推力（Cande and Stegman, 2011）的基础上，除了作用在系统上的板片拉力和山脊推力之外，它可能在解释印度的快速运动方面发挥作用。目前的观察表明，地幔柱会影响板块运动以及板块边界的形成位置，但其潜在的物理过程如何以及为何尚不清楚。地幔对流的数值模型将用于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约束。此外，羽流推力作用的物理机制将通过地球动力学模型进行定量研究。最后，该项目将研究允许羽流在短时间间隔（5-10 Myr）内促进板块边界重组的物理机制，如塞舌尔微板块在 70-60 Ma 之间的构造历史所示，可用于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板块构造建模的能力：作为一个完全动态、与时间相关的 3D 系统，具有自我一致演化的板块驱动力。