Displaced and Faded - How Thermodynamics and Kinetics Collude to Complicate Seismic Structures in Earth's Mantle

Explore how thermodynamics and kinetics combine to create complex seismic structures in Earth's mantle through this 57-minute lecture from the University of Liverpool's Earth Sciences department. Discover why Earth's 410 km discontinuity exhibits varying seismic expressions, from sharp, high-amplitude interfaces to broad weak signals that equilibrium thermodynamics alone cannot fully explain. Learn about laboratory findings showing that the olivine ⇔ wadsleyite transition is strongly rate-limited, suggesting kinetics significantly influence seismic structures despite uncertainties in growth and nucleation spanning several orders of magnitude. Examine how researchers embed growth-controlled kinetic models into compressible geodynamic simulations of mantle plumes and slabs to quantify kinetic effects on seismic structures. Understand the different behaviors of plumes versus slabs: plumes follow smooth, monotonic trends where sluggish kinetics broaden and uplift the 410 while faster kinetics sharpen it, whereas slabs display thresholded behavior with moderately-slow kinetics generating metastable wedges and broad phase transition zones. Investigate kinetic thresholds of approximately less than 1 1/Ma that separate metastable slab ponding regimes from equilibrated slab penetrating ones, providing direct links between kinetic rates and seismic signatures in subduction zones. Gain insights into how these findings reconcile observed lateral variability in 410 topography and sharpness across hotspots and subduction zones, establishing the 410 as a sensitive seismological probe of phase transition kinetics and demonstrating the essential role of incorporating kinetics into compressible geodynamic simulations for connecting mineral-scale processes to mantle-scale dynamics.