Earth’s mantle is far from a uniform reservoir; it is a complex archive of our planet’s formation and evolution. From the lithosphere to the core-mantle boundary, heterogeneities provide critical clues to mantle convection, differentiation, and recycling. This session explores the nature and origins of enigmatic discontinuities and anomalies of multiple scales throughout the mantle and transition zone.

We invite contributions that utilize innovative approaches in seismology, geodynamics, geochemistry, and mineral physics to test competing hypotheses for the origin of these structures: Are they signatures of subducted crust, volatile-induced melting, or primordial reservoirs? We particularly welcome studies that introduce new observational frameworks or multi-disciplinary approaches to distinguish between thermal and compositional origins. By integrating perspectives across Earth and other rocky planets, this session aims to showcase discoveries that redefine our understanding of deep-Earth dynamics and the long-term evolution of planetary interiors.