UCLA

The long-term carbon cycle on million-year timescales is shaped by planetary interior evolution, which governs CO2 outgassing, volatile recycling, topography, and ocean-floor bathymetry. Because marine sediments and lithified carbonates represent the largest hydrosphere-accessible carbon sink through much of Earth history, changes in bathymetry, continental flooding, and ocean basin geometry may strongly influence ocean-atmosphere chemistry. This dissertation investigates how solid-Earth evolution controls bathymetry, ocean basins, and the long-term carbon cycle across Earth history and rocky ocean-world analogs.First, I reconstruct bathymetry over the last 80 Myr and evaluate its carbon-cycle consequences using an Earth system model of intermediate-complexity (EMIC). These results show that evolving seafloor geometry significantly affects ocean chemistry and carbon partitioning. Faster tectonics produces shallower pelagic oceans and greater continental flooding, reducing deep-ocean carbon sequestration. However, pelagic bathymetry and shallow shelf area can evolve independently, producing competing effects on carbon storage under different climatic and sea-level states.Second, I develop slabmodellib, a kinematic subduction framework that reconstructs slab histories from plate-motion and seafloor-age models, incorporates slab deflection at the ringwoodite–bridgmanite phase transition, and computes the resulting non-hydrostatic geoid and dynamic topography. Applied to the last 80 Myr, the model shows that mantle-driven topography and geoid anomalies reorganize coastline length and seafloor area without a simple linear relationship. Dynamic topography generally supports shallow shelves, reduces intermediate-depth seafloor, and has smaller effects on deep-ocean area, implying that mantle flow can alter carbon-cycle boundary conditions by redistributing shelf and pelagic carbon sinks.Finally, I develop ExoCcycle, a graph-theory community-detection framework for objectively defining ocean basins from single or stacked scalar fields on a sphere. By applying Louvain, Leiden, and Girvan-Newman methods to bathymetry and related fields, ExoCcycle identifies consistent basin boundaries for paleo reconstructions and statistically constrained exoplanet topographies. This enables basin-scale data aggregation, model assimilation, and objective spatial domains for reduced-order carbon-cycle and volatile-cycle models.Together, these results show that the solid Earth influences the long-term carbon cycle not only through volcanic forcing and recycling, but also by shaping the geometry, depth distribution, and connectivity of ocean basins on Earth and other rocky ocean worlds.