Claire Richardson: The Mysterious, Massive Structures in Earth's Deep Mantle

WSU Physics Colloquium: 16 January 2025

Claire Richardson: The Mysterious, Massive Structures in Earth's Deep Mantle

For over a century, seismologists have measured and modeled earthquake waves to determine Earth's interior structure. Early work by Inge Lehmann, Beno Gutenberg, and Andrija Mohorovičić revealed global internal physical discontinuities, ultimately yielding the basic layer-cake structure of the crust,
mantle, and inner and outer core that we see in textbooks. These fundamental discoveries were made from extremely sparse seismic data, and this simple layered model has been and continues to be the
first-order understanding of the interior of the Earth. In the 1980s, however, seismologists discovered anomalous waveforms that suggested the existence of two very large structures sitting nearly antipodal on the core-mantle boundary (CMB). These structures, characterized by lower-than-average wave speeds relative to the ambient mantle rock, are referred to as Large Low-Velocity Provinces (LLVPs). Since the initial discovery of the LLVPs, the quantity of data has skyrocketed, theoretical modeling frameworks have advanced profoundly, and computational resources have proliferated. These three factors have fundamentally transformed our understanding of Earth’s deep interior. At the CMB, a boundary layer delineating an even more extreme change in physical properties than between the crust and the atmosphere, they have revealed a tremendously complex landscape dominated by the LLVPs. In this talk, I will give an overview of the discovery of the LLVPs and present the current
knowledge and interpretations of the physical nature of the CMB. I’ll also discuss open questions and active areas of multidisciplinary research to improve our understanding of LLVPs as we continue to unravel the mysteries of this complex region of our planet.