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ORIGINAL PAPER

The structure of the lithosphere and upper mantle beneath the Eastern Mediterranean and Middle East Dan McKenzie1  Received: 5 October 2020 / Revised: 10 October 2020 / Accepted: 13 October 2020 / Published online: 20 November 2020 © The Author(s) 2020

Abstract Surface velocity measurements show that the Middle East is one of the most actively deforming regions of the continents. The structure of the underlying lithosphere and convecting upper mantle can be explored by combining three types of measurement. The gravity field from satellite and surface measurements is supported by the elastic properties of the lithosphere and by the underlying mantle convection. Three dimensional shear wave velocities can be determined by tomographic inversion of surface wave velocities. The shear wave velocities of the mantle are principally controlled by temperature, rather than by composition. The mantle composition can be obtained from that of young magmas. Application of these three types of observation to the Eastern Mediterranean and Middle East shows that the lithosphere thickness in most parts is no more than 50-70 km, and that the elastic thickness is less than 5 km. Because the lithosphere is so thin and weak the pattern of the underlying convection is clearly visible in the topography and gravity, as well as controlling the volcanism. The convection pattern takes the form of spokes: lines of hot upwelling mantle, joining hubs where the upwelling is three dimensional. It is the same as that seen in high Rayleigh number laboratory and numerical experiments. The lithospheric thicknesses beneath the seafloor to the SW of the Hellenic Arc and beneath the NE part of the Arabian Shield are more than 150 km and the elastic thicknesses are 30–40 km. Keywords  Mediterranean · Middle East · Lithosphere · Gravity · Seismic structure · Mantle convection · Melting

1 Introduction Since its discovery in 1967 it has been clear that plate tectonics only provides a good description of oceanic plate boundaries. On continents earthquakes are not confined to narrow belts (Isacks et al. 1968), and this distribution is not the result of location errors. This difference between oceans and continents is why plate tectonics was not discovered by geologists working on land. One of the first applications of the new methods to continental deformation was to the western part of the Alpine-Himalayan Belt by McKenzie (1972), who showed that most of the convergence between Electronic supplementary material  The online version of this article (https​://doi.org/10.1007/s4299​0-020-00038​-1) contains supplementary material, which is available to authorized users. * Dan McKenzie [email protected] 1



Department of Earth Sciences, University of Cambridge, Bullard Laboratories, Madingley Road, Cambridge CB3 0EZ, UK

Africa and Europe in the Eastern Mediterranean was taken up by the rapid westward motion of Anatolia and by subduction of the Eastern Mediterranean beneath the Hellenic Arc, and not by shortening on east–west striking thrusts.