The dynamic life of an oceanic plate
Abstract As the Earth's primary mode of planetary cooling, the oceanic plate is created at mid-ocean ridges, transported across the planet's surface, and destroyed at subduction zones. The evolution of its buoyancy and rheology during its lifespan maintains the coherence of the plate as a distinct geological entity and controls the localised deformation and vertical material exchange at plate boundaries, which enables the horizontal ocean-plate movements. These motions intimately link the oceanic plate to the overarching overturn of Earth's mantle: The plate forms out of rising mantle material at spreading ridges; it cools the Earth's interior as the cold thermal boundary layer to mantle convection; and its sinking portions drive not only the plate itself but also dominate global flow in the mantle. We scrutinise here the entire life cycle of the oceanic plate, starting with its birth at the mid-ocean ridge, including the thermal, rheological, and chemical conditions of initiation, followed by plate maturation as it ages and cools while crossing the seafloor, and finishing with the dynamics of plate destruction as it retires at the subduction zone to become a deeper part of Earth's convective system. We find that the full range of dynamic behaviour of the oceanic plate, including its forcing and overall framework within Earth's convecting system, is not fully captured by the existing concept of Plate Tectonics, which describes solely the horizontal surface kinematics of all plates. Therefore, we introduce a more specific and at the same time more integral concept named “Ocean-Plate Tectonics” that more specifically describes the dynamic life of the oceanic plate and accounts for the knowledge gained during the past 50 years. This “Ocean-Plate Tectonics” must have emerged on Earth at least 1 Billion years ago, and dominates Earth's dynamics today.