Small-scale instabilities below the cooling oceanic lithosphere |
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| Authors: | Gabriele Marquart Harro Schmeling & Alexander Braun |
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| Institution: | Institut für Meteorologie und Geophysik, Universität Frankfurt, Feldbergstr. 47, D 60323 Frankfurt, Germany. E-mail:;-frankfurt.de;-frankfurt.de;-frankfurt.de |
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| Abstract: | Interpretation of satellite altimetry data as well as ship bathymetry data revealed strongly elongated anomalies roughly perpendicular to the mid-ocean ridges in the Indian and east Pacific oceans. A spectral analysis of gravity altimetry data along profiles parallel to the East Pacific Rise indicated wavelengths of about 150–180 km close to the ridge and about 250 km further away. A simple model of Rayleigh–Taylor instabilities developing at the base of the cooling lithosphere is discussed and applied to the data. By considering thermal diffusion and comparing Rayleigh–Taylor growth rates to the velocity of the thermal front in the cooling lithosphere, we are able to explain the observed anomalies by instabilities developing below the lithosphere in a layer with a viscosity of about 1019 Pa s above an asthenospheric layer with a viscosity reduction of 2–3 orders of magnitude. |
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| Keywords: | lithospheric cooling mid-ocean ridges Rayleigh aylor instabilities SE Pacific upper mantle viscosity |
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