Towards an improved understanding of the mechanical properties and rheology of the lithosphere: an introductory article to ‘Rock Deformation from Field, Experiments and Theory: A Volume in Honour of Ernie Rutter’

Abstract

Ernie Rutter’s influential contribution to our understanding of rock deformation spans the whole continental crust, from deformation ‘just under the grass’ (e.g. Rutter & Green 2011) to melt migration in the lower crust (e.g. Rutter & Neumann 1995). Ernie has also worked on many aspects of the deformation of oceanic crust (Rutter & Brodie 1988); however, here we reflect on the wide range of deformation conditions Ernie has studied by presenting key aspects of the strength and rheology of the continental lithosphere as we understand it today, with the aim of providing the context for the contributions included within this volume. The continental crust forms just over a third of the Earth’s surface and it is different from the crust of any other planet in our solar system. It is rich in those elements that partition in a silicate melt and its formation and evolution determined the composition of the mantle and that of the atmosphere (Hawkesworth 2006). Thanks to its physical and chemical fingerprint, the Earth’s crust has sustained life uninterrupted for 3.8 Ga and it is the source of major natural resources such as hydrocarbons and mineral deposits and others such as geothermal energy. The continental crust is less dense than its oceanic counterpart, and is therefore more buoyant. It forms a substantial part of the cold thermal layer of the Earth and its rheology (from Greek r1v rheō, ‘flow’ and -logia, -logia, ‘study’; ‘the study of the flow of matter’) is a key factor controlling plate tectonic processes at the Earth’s surface and in its interior (Davies 2011). Beneath the continental crust lies the lithospheric mantle and together they form the continental lithosphere. Considerable variations in structure, thickness and composition of the continental lithosphere mean that, despite its importance, we currently have limited understanding of the rheology of this complex system (Thatcher & Pollitz 2008). Significant advances in our knowledge of continental rheology have been possible through: