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Book Chapter

The role of magmatism in continental rifting

Published:
January 01, 2016

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.

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Contents

Geological Society, London, Special Publications

Magmatic Rifting and Active Volcanism

T. J. Wright
T. J. Wright
University of Leeds, UK
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A. Ayele
A. Ayele
Addis Ababa University, Ethiopia
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D. J. Ferguson
D. J. Ferguson
University of Leeds, UK
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T. Kidane
T. Kidane
Addis Ababa University, Ethiopia
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C. Vye-Brown
C. Vye-Brown
British Geological Survey, UK
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Geological Society of London
Volume
420
ISBN electronic:
9781862391345
Publication date:
January 01, 2016

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