Seismology is by far our most important tool for studying Earth's deep interior. Surface recordings of seismic waves generated by Earthquakes are combined to image the three-dimensional variations in seismic velocities. With additional inforation from mineral physics, these images can be interpreted in terms of thermal and compositional anomalies allowing us to study deep dyanmic processes that are vital to life on Earth. For several decades, seismology has imaged two continent-sized structures in the deepest mantle underneath the Pacific and Africa. These two structures rise hundreds of kilomteres above the core-mantle boundary and show velocity reductions of a few percent. Despite being imaged consistently over the years, their material properties and origins remain enigmatic. Are they chemically distinct, stable over geological time scales and the hosts of hidden geochemical reservoirs? Or are they hot superplumes that are passively swept over the core's surface due to subducting slabs? Distinguishing between both end-member scenarios is imporant as these structures may significantly alter the cooling efficiency of the mantle and thus the thermal history of the Earth. In this contribution, I shall explain why we need to get a grip on the nature of these continental-size structures and detail the progress we have made over recent years. Paricularly I shall emphasize that seismic velocities are not able to provide definitive answers, but that we need to include additional observations and collaborations across disciplines, drawing in knowledge from geodynamics, seismology, geodesy, and mineral physics. Finally I shall demonstrate how we are slowly converging on scenarios with a balance between thermal and chemical anomalies, allowing us to put some constraints on what these structures are made off.

Continent-sized structures at the bottom of the mantle: how we use seismology to investigate what they are made off 
Paula Koelemeijer. Dept. Earth Sciences, Royal Holoway, University of London, UK

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.

Continent-sized structures at the bottom of the mantle: how we use seismology to investigate what they are made off Paula Koelemeijer. Dept. Earth Sciences, Royal Holoway, University of London, UK