RSES Seminar Series 2022-09-15 Nicolas Flament (University of Wollongong)

Setting the lower mantle free
Nicolas Flament (University of Wollongong)
Abstract: Plate tectonics shapes Earth’s surface, and is linked to motions within its deep interior. Cold oceanic lithosphere sinks into the mantle, and hot mantle plumes rise from the deep Earth, leading to volcanism. Volcanic eruptions over the past 320 million years have been linked to two large structures at the base of the mantle presently under Africa and the Pacific Ocean. This has led to the hypothesis that these basal mantle structures could have been stationary over geological time, in contrast to observations and models suggesting that tectonic plates, subduction zones and mantle plumes have been mobile. Here we reconstruct mantle flow from one billion years ago to the present day to show that the history of volcanism is statistically as consistent with mobile basal mantle structures as with fixed ones. In our reconstructions the structure beneath Africa progressively assembled from 400 million years ago, pushed by sinking oceanic lithosphere, to become a coherent structure as recently as 60 million years ago. In contrast to previous suggestions, our mantle flow models suggest that basal mantle structures are mobile, and aggregate and disperse over time, similarly to continents at Earth’s surface.
Bio: Nicolas Flament is a Senior Lecturer at the University of Wollongong. He graduated in 2010 with a PhD in Earth Sciences from École Normale Supérieure de Lyon and The University of Sydney (cotutelle). He investigates the deformation of the solid Earth over tens of million years by merging geodynamic models with global geological observations in collaboration with Earth Scientists in academia and in industry.