4D physical models of migrating mid-ocean ridges: Implications for shallow mantle flow, melt distribution and seafloor topography

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Plate tectonics and planetary convection in the form of mid-ocean ridge spreading, plate subduction and mantle plumes drive the natural mass/energy cycling of the solid earth-hydrosphere-atmosphere system over geological time scales and provides important context for present day global climate change. It is estimated that roughly half of the carbon provided to the hydrosphere/ atmosphere from magmatic processes generated by these geological drivers is attributed to plate spreading of the world's 80,000 km long mid-ocean ridge system. This project will use a physical laboratory apparatus to develop improved models of convective mantle flow driving plate motion and magmatic production beneath mid-ocean ridges by characterizing the essential processes not only in 3-dimensions but also their time evolution. Previous models that attempt to connect mantle flow, magma production and mass/energy flux to Earth's oceans/atmosphere have typically only been conducted in two-dimensions. The combination of recent geological and geophysical data and model upgrades clearly show that 2D model representations are insufficient. The project includes support for a graduate student and research opportunities for undergraduates from under-represented groups including local native american students through the Research Experience for Undergraduates program at the University of Rhode Island. Physical models will also provide a visually accessible experience of deep earth processes for university, school and public outreach audiences.This project will design and construct geodynamic models that build and expand on established and tested laboratory apparatus for exploring the essential four-dimensional processes related to mid-ocean spreading ridges. While numerical models suffer from resolution issues and are approximations to a set of governing equations with errors that are usually entirely unknown, physical models are particularly useful as they permit high resolution 3D physics with a natural time dependency in regions of interest (e.g. in the melt generation regions beneath ridges) and allow model boundary artifacts to be minimized. The project will investigate both basic ridge geometries and models with more complex attributes such as mid-ocean ridge migration and its role on upper mantle dynamics, seafloor topography, and mid-ocean ridge magmatic processes. This new lab apparatus will investigate several previously proposed but untested models: (1) asymmetric upwelling of the upper mantle below the leading tectonic plate, (2) asymmetric distribution of seamounts across migrating mid-ocean ridge systems, (3) magmatic segmentation and melt scavenging of offset mid-ocean ridges, and (4) enhanced upwelling at ridge-transform intersections. The design of the migrating ridge apparatus will allow transform offsets, spreading rates, and migration vectors that can scale to the full spectrum of known mid-ocean ridge systems. The laboratory model and suite of modeling results will provide a unique test of the 4D character of mid-ocean ridges and provide insight into geodynamic and melting processes at mid-ocean spreading centers. Results are expected to have important implications for understanding fundamental mantle processes and how these influence mass/energy fluxes to the hydrosphere/atmosphere systems on geologic time scales. These models will also provide important benchmarks for related fields, such as mantle properties, seismic tomography and estimates of absolute plate motions.