EAR-PF: Mantle Convection Modeling as a Test of Pacific Absolute Plate Motion

Daniel Woodworth 博士获得了 NSF EAR 博士后奖学金，在 Jonny Wu 博士的指导下在休斯顿大学开展研究和教育项目。该研究将评估太平洋盆地岩石圈的运动模型，岩石圈是地球最外层的坚固层，由整个地壳和上地幔组成。岩石圈被分成板块——作为单个单元移动的部分。位于太平洋大部分区域下方的太平洋板块是其中最大的板块。但由于它被海洋覆盖，重建它相对于地球其他部分的运动具有挑战性。已经开发了几种竞争模型。伍德沃斯博士将把地幔的结构与每个板块运动模型预测的结构进行比较。区分太平洋板块运动模型将使科学家能够更好地了解构造板块如何以及为何运动。随附的教育计划将重点关注西班牙裔社区的 STEM 推广，包括开发介绍地球物理概念的西班牙语-英语双语主动学习模块。该研究将测试夏威夷热点轨道上西北走向的皇帝海山链和西北走向的夏威夷链之间约 60° 夏威夷-皇帝弯曲 (HEB) 形成前后的太平洋板块运动模型。著名的早期太平洋绝对板块运动（APM）模型将 HEB 归因于板块运动相对于固定热点的变化，这与固定热点近似一致，固定热点近似已用于定义近似绝对参考系。然而，最近的分析认为，HEB 相反反映了热点运动的变化，而板块运动没有发生大的变化，这表明热点运动是快速的。该项目将使用这些端元 APM 来使用并行前向对流代码 TERRA 驱动整个地幔循环模型，并将预测的地幔结构、合成大地水准面和动态地形与观测结果进行比较。本研究的目的是确定（1）HEB 时太平洋板块运动的恒定或变化是否能更好地解释目前的观测结果，从而（2）热点和板块运动的特征时间尺度是否有足够的差异，使得热点运动相对于板块运动可以被认为可以忽略不计。此外，通过检查由局部板块运动驱动的全球地幔对流模型的预测，它探索了局部岩石圈规模的过程与地幔规模的过程之间的关系。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Dr. Daniel Woodworth has been awarded an NSF EAR Postdoctoral Fellowship to conduct research and education projects at the University of Houston under the mentorship of Dr. Jonny Wu. The study will evaluate models of the motion of the lithosphere, Earth’s outermost strong layer, consisting of the entire crust plus the upper mantle, in the Pacific Ocean basin. The lithosphere is divided into plates – segments that move as single units. The Pacific Plate, which underlies much of the Pacific Ocean, is the largest of these. But because it is covered by ocean, reconstructing its movement relative to the rest of Earth is challenging. Several competing models have been developed. Dr. Woodworth will compare the structure of the mantle with that predicted by each model of plate motion. Distinguishing between models of Pacific Plate motion will allow scientists to better understand how and why tectonic plates move. The accompanying educational plan will focus on STEM outreach to the Hispanic community, including developing Spanish-English bilingual active learning modules that introduce geophysical concepts.The study will test models of Pacific Plate motion before and after the formation of the ~60° Hawaiian-Emperor Bend (HEB) between the north-northwest trending Emperor Seamount Chain and the west-northwest trending Hawaiian Chain in the track of the Hawaiian Hotspot. Prominent early Pacific absolute plate motion (APM) models attributed the HEB to a change in plate motion relative to a stationary hotspot, consistent with the fixed-hotspot approximation, which had been used to define an approximate absolute reference frame. However, more recent analyses have argued that the HEB instead reflects a change in hotspot motion without a large change in plate motion, suggesting rapid hotspot motion. This project will use these endmember APMs to drive whole-mantle circulation models using the parallel forward convection code TERRA and compare the predicted mantle structures, synthetic geoids, and dynamic topography to observations. The objectives of this study are to determine (1) whether constant or changing Pacific Plate motion at the time of HEB better explains present observations and thus (2) whether the characteristic temporal scales of hotspot and plate motion are sufficiently different such that hotspot motion may be considered negligible relative to plate motion. Further, by examining the predictions of global mantle convection models driven by local plate motion it explores the relationship between processes operating at the scale of the local lithosphere and processes at the scale of the mantle.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.