Editors’ Highlights are summaries of recent papers by AGU’s journal editors.
Source: Geochemistry, Geophysics, Geosystems
Throughout Earth’s history, heat flow from the core into the base of the mantle should have occasionally destabilized the bottom boundary and launched thermal plumes. Whether these plumes reach the surface and cause the formation of large igneous provinces and hotspots depends on their ability to cross the mantle transition zone, 410-660 kilometers deep. This is known to depend on the interaction of the thermal buoyancy of the plume with the density changes associated with a series of mineralogical phase transitions that mantle rocks experience in this depth range. Plumes plainly reach the surface at present-day mantle temperatures, leading to events like continental flood basalts and persistent hotspots, such as Hawaii. But, what about in the past, when the mantle was thought to be significantly hotter? Numerical models of mantle convection have struggled to address this question because it requires self-consistent consideration of the mineralogical phase equilibria, the latent heat of the phase transitions, and the density of the various minerals.
Li et al. [2025] introduce an update to the popular convection software ASPECT that allows the authors to look at the interaction of mantle plumes with the transition zone across a wide range of mantle temperatures. The essential innovation is that the equation expressing conservation of energy in the model is formulated with entropy rather than temperature as an independent variable. Combined with the HeFESTO thermodynamic model, which predicts not only where the phase transitions take place but how entropy and density change across them, this model properly handles the thermochemical and buoyancy effects of the mantle phase transitions.
The authors conclude that there was an early era when most plumes would have stagnated at the transition zone, followed by a transition, perhaps between 1.5 and 0.75 billion years ago, when it became more common for plumes to break through and reach the surface. Given the ability of large igneous events to strongly perturb the biosphere through massive volcanic outgassing, this result will influence thinking not only about mantle circulation but also the magnitude of perturbations experienced at the surface over time.
Citation: Li, R., Dannberg, J., Gassmöller, R., Lithgow-Bertelloni, C., & Stixrude, L. (2025). How phase transitions impact changes in mantle convection style throughout Earth’s history: From stalled plumes to surface dynamics. Geochemistry, Geophysics, Geosystems, 26, e2024GC011600. https://doi.org/10.1029/2024GC011600
—Paul Asimow, Editor, Geochemistry, Geophysics, Geosystems