Stability of the oceanic lithosphere with variable viscosity: an initial-value approach

David A. Yuen, Luce Fleitout

Research output: Contribution to journalArticle

36 Scopus citations

Abstract

We have studied the problem concerning the onset of convective instabilities below the oceanic lithosphere. A system of linear partial differential equations, in which the background temperature field is time-dependent, is integrated in time to monitor the evolution of incipient disturbances. Two types of rheologies have been examined. One depends strongly on temperature. The other involves a viscosity which is both temperature- and pressure-dependent. The results from this initial-value approach, in which the viscosity profiles migrate downward with time, reveal the importance of considering temperature- and pressure-dependent rheology in issues regarding the development of local instabilities in upper mantle convection. For temperature-dependent viscosity, viscosities of 0(1020P) are required to produce instabilities with growth-rates of 0(.1/Ma). In contrast, these same growth rates can be attained for a temperature- and pressure-dependent viscosity profile with a mean value close to 0(1020P) in the upper mantle, owing to the presence of a low viscosity zone, 0(1020P), existing right below the lithosphere. Unlike the results of temperature-dependent viscosity, whose growth-rates increase with time, the amplification of disturbances in a fluid medium with temperature- and pressure-dependent rheology reaches a maximum at an early age, < 50 Ma, and decreases thereafter with time. This suggests the potential importance played by initial disturbances in the evolution of the oceanic lithosphere.

Original languageEnglish (US)
Pages (from-to)173-185
Number of pages13
JournalPhysics of the Earth and Planetary Interiors
Volume34
Issue number3
DOIs
StatePublished - Jul 1984

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