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

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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.