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

Daniel Woodworth博士被授予NSF EAR博士后奖学金，在休斯敦大学Jonny Wu博士的指导下进行研究和教育项目。这项研究将评估岩石圈运动的模型。岩石圈是地球最外层的坚固层，由整个地壳加上上地幔组成，位于太平洋盆地。岩石圈被划分成板块——作为单个单元运动的板块。位于太平洋下部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是具有挑战性的。已经开发了几种相互竞争的模型。伍德沃斯博士将把地幔的结构与每个板块运动模型所预测的结构进行比较。区分太平洋板块运动的不同模型将使科学家更好地理解板块运动的方式和原因。配套的教育计划将侧重于STEM向西班牙裔社区的推广，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。该研究将在夏威夷热点的轨道上测试~60°夏威夷-皇帝弯曲（HEB）形成前后的太平洋板块运动模型，该弯曲位于西北偏北走向的皇帝海山链和西北偏西走向的夏威夷链之间。早期著名的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，固定热点近似被用来定义一个近似的绝对参考框架。然而，最近的分析认为，HEB反而反映了热点运动的变化，而没有板块运动的大变化，表明热点运动迅速。该项目将使用这些端元APMs来驱动使用平行正流式代码TERRA的全地幔环流模型，并将预测的地幔结构、合成大地面线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时太平洋板块的恒定运动或变化运动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足够不同，以至于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，探讨了在局部岩石圈尺度上运行的过程与在地幔尺度上运行的过程之间的关系。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识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.