Revised Predictions of the Properties and Behavior of Oceanic Lithosphere for Half-Space and Plate Models

Models of oceanic lithosphere use empirical parameters such as the observed subsidence rate, heat flow, thermal expansivity, thermal diffusivity, mantle temperature, and others as constraints on the best fitting and most realistic models. Using new estimates of global seafloor subsidence, area-age distribution, and thermal expansivity it is demonstrated that half-space models predict net seafloor heat flux as low as 18 TW if the apparent thermal expansivity is not lower than that measured. Using the classical apparent thermal expansivity (>20% lower than measured), seafloor heat flow is still not greater than about 24 TW, still about 30% lower than conventional estimates (~32 TW). This prediction is partly related to a reappraisal of the seafloor area-age distribution and partly associated with the prediction of a low thermal diffusivity on the order of 0.65 mm² s^-1. The low thermal diffusivity predicts slow cooling and old-age seafloor heat flow is too low to reproduce observations without an extremely thin plate (<80 km). In this light, I submit the following possibilities for the coupled explanation of seafloor topography and old-age heat flow: A) the subsidence rate is higher than ~330 m My^-1/2, B) the apparent thermal expansivity is more than 25% lower than measured, C) there is a strong time-dependence in the effective properties of the lithosphere, D) the half-space and plate models are inadequate to explain observations.