Mantle Convection at Earth-like Vigor: Thermal Plumes Reconcile Hot–spot Observations

Hot–spots are anomalous regions of magmatism that cannot be directly associated with plate tectonic processes. They are widely regarded as the surface expression of hot, columnar plumes, upwelling from deep within Earth’s 2900–km thick mantle. Hot–spots have variable life–spans, magmatic productivity and fixity. This suggests that a wide– range of upwelling structures co–exist within Earth’s mantle, a view supported by both geochemical and seismic evidence. However, to date, numerical convection studies have failed to reproduce such behavior, predicting either very stable or highly time–dependent plumes. Here, we present results from a global 3–D spherical mantle convection model that better reconcile hot–spot observations. The major modification from previous work is that, owing to a highly–efficient multi–resolution solution algorithm, our model more accurately replicates the dynamical regime of Earth’s mantle, which convects at a Rayleigh number of order 10. We discover strong upwellings that extend from the core–mantle boundary to the surface. These show a broad range of behavior; some drift slowly, while others are more mobile and ephemeral, displaying variable life–spans, intensities and migration velocities. Such behavior is consistent with observations on Earth, indicating that it is essential to simulate Earth’s mantle at the correct Rayleigh number and in the appropriate geometry to reproduce Earth–like dynamics. Thermal processes alone are sufficient to explain the principal features of upwellings on Earth.