CSEDI Collaborative Research: Deciphering the LLSVP-plume relationship

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Much of our view of mantle evolution is shaped by our current knowledge of mantle convection and plume dynamics; examples include hotspot volcanism--including large igneous provinces--and mantle mixing. By gaining a deeper understanding of how, where, and why plumes form, and their composition and their relationship to the deep interior's large low shear wave velocity structures (LLSVPs) under Africa and the Pacific, the PIs will make a significant step towards understanding the dynamical and geochemical evolution of the mantle. Their efforts should provide a basis to better understand the three-dimensional flow structure surrounding LLSVPs and where, how, and why plumes form. This may help answer the question: How is the relationship between plumes and LLSVPs reflected in hotspot lavas such as those found in Hawaii? The new research directions will enrich cross-fertilization between the fields of mantle dynamics and geochemistry and contribute to the growing body of work on mantle plumes and LLSVPs. The PIs are engaged in a number of activities aimed at education and training at all levels. The PIs have and will continue to engage undergraduate students, including those from underrepresented groups in their research activities. As part of this proposal the PIs aim to augment the content associated with related Wikipedia entries and develop a series of educational films to post on specifically dedicated YouTube channels. The lab lends itself to site visits by elementary, middle school and high school students. PI Lithgow-Bertelloni intends to continue providing lab tours and opportunities for elementary and middle-school children to be involved in simple experiments.Amongst the most enigmatic aspects of the Earth's deep interior are the anomalous large low shear wave velocity provinces (LLSVPs) under Africa and the Pacific. The origin, composition, and dynamics of these provinces remain controversial. For example, it has been suggested that plumes predominantly form at the edges of LLSVPs and that entrained material from LLSVPs explains the distinct chemical asymmetries found at certain hotspots. The PIs are proposing an experimental fluid dynamical study to explore how three proposed LLSVP structures control and interact with mantle plumes. These three structures represent the range of LLSVP formation hypotheses so far proposed: a) purely thermal; b) dense and deformable; c) undeformable and uncoupled. They will use state-of-the-art visualization tools, including scanning particle image velocimetry and thermometry to measure the three-dimensional temperature and flow fields, laser induced fluorescence, and Lagrangian analysis tools to locate plumes and quantify entrainment to very high spatial and temporal resolutions. The PIs seek to test both location control and whether entrainment at the edges explains the observed chemical asymmetry in hotspot lavas.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.