Breaking supercontinents; no need to choose between passive or
Martin Wolstencroft1,2 and Huw Davies21JBA Risk Management, Skipton, UK 2School of Earth and Ocean Sciences, Cardiff University, CF10 3YE, Wales, UK
Received: 05 Feb 2017 – Accepted for review: 07 Feb 2017 – Discussion started: 08 Feb 2017
Abstract. Much debate has centred on whether continental break-up is predominantly caused by active upwelling in the mantle (e.g. plumes) or by long-range extensional stresses in the lithosphere. We propose the hypothesis that global supercontinent break-up events should always involve both. The fundamental principle involved is the conservation of mass within the spherical shell of the mantle, which requires a return flow for any major upwelling beneath a supercontinent. This shallow horizontal return flow away from the locus of upwelling produces extensional stress. We demonstrate this principle with numerical models, which simultaneously exhibit both upwellings and significant lateral flow in the upper mantle. For non-global break-up the geometry of the mantle will be less influential, weakening this process. This observation should motivate future studies of continental break-up to explicitly consider the global perspective, even when observations or models are of regional extent.
Wolstencroft, M. and Davies, H.: Breaking supercontinents; no need to choose between passive or
active, Solid Earth Discuss., doi:10.5194/se-2017-14, in review, 2017.