Why is Africa rifting?

J M Kendall, Carolina Lithgow-Bertelloni

Research output: Chapter in Book/Report/Conference proceedingChapter in a book

12 Citations (Scopus)
377 Downloads (Pure)

Abstract

Continental rifting has a fundamental role in the tectonic behaviour of the Earth, shaping the surface we live on. Although there is not yet a consensus about the dominant mechanism for rifting, there is a general agreement that the stresses required to rift the continental lithosphere are not readily available. Here we use a global finite element model of the lithosphere to calculate the stresses acting on Africa. We consider the stresses induced by mantle flow, crustal structure and topography in two types of models: one in which flow is exclusively driven by the subducting slabs and one in which it is derived from a shear wave tomographic model. The latter predicts much larger stresses and a more realistic dynamic topography. It is therefore clear that the mantle structure beneath Africa plays a key part in providing the radial and horizontal tractions, dynamic topography and gravitational potential energy necessary for rifting. Nevertheless, the total available stress (c. 100 MPa) is much less than that needed to break thick, cold continental lithosphere. Instead, we appeal to a model of magma-assisted rifting along pre-existing weaknesses, where the strain is localized in a narrow axial region and the strength of the plate is reduced significantly. Mounting geological and geophysical observations support such a model.
Original languageEnglish
Title of host publicationMagmatic Rifting and Active Volcanism
EditorsTJ Wright, A Ayele, DJ Ferguson, T Kidane, C Vye-Brown
Place of PublicationLondon
Pages31-42
Number of pages12
DOIs
Publication statusPublished - 2016

Publication series

NameGeological Society Special Publications
PublisherThe Geological Society of London
Volume420
ISSN (Print)0305-8719
ISSN (Electronic)2041-4927

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