Geodynamic Considerations of the Development of the Hellenides
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The Hellenic Arc is tectonically controlled by a lithothermal system which is ascending from the asthenosphere into the lithosphere. This forces an upwards movement in the crust of several kilometers vertical displacement. The sedimentary cover is partially eroded and through gravitative sliding removed from its original position.
The crust is thickened at the outer zones of the Hellenides, due to the great amount of sialic material compressed in this area. The hot upper-mantle material moves outwards to the SW, S and SE, overriding the crust of the Ionian and the Levantine Seas. This partly causes the subduction of the thinner crust of the seas below the continental Aegean crust, and initiates intermediate depth earthquakes. The downbuckled light crust in the miogeosynclinal zone is isostatically undercompensated. The downfolding process stops at the moment the buoyancy of the light material gets too large to permit further subsidence. The process gets shifted further out and initiates a new mountain-building phase to start.
This is presently occurring at the Mediterranean Ridge, which shows an increase of crustal thickness, accumulation of light material and also deeper earthquakes than normal. The Aegean volcanic arc has developed along a zone of crustal weakness and deep faults that dislocate crustal continuation between the Cycladic Massive and the Cretan Sea (Makris et al. 1977).
In Fig. 1 a crustal cross section deduced from seismic and gravity data is presented.
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| For figure please refer to book. | |
| Figure mentioned in this paper: | |
| Fig. 1: | Crustal cross section deduced from seismic and gravity data. |
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| Source: | "Thera and the Aegean World II" |
| Papers and Proceedings of the Second International Scientific Congress, Santorini, Greece, August 1978. | |
| Pages: | pp. 43 - 44 |
| Written by: | J. Makris |
| Institute of Geophysics, University of Hamburg, Germany. | |
| Book information: | |
| ©Thera and the Aegean World | |
| ISBN: | 0 9506133 2 0 |
| Published by: | Thera and the Aegean World, 105-109 Bishopsgate, London EC2M 3UQ |
| Editor: | C. Doumas |
| To order the book from amazon.co.uk: | http://www.amazon.co.uk/exec/obidos/ASIN/0950613320/qid=1142346164/sr=1-4/ref=sr_1_0_4/026-5808754-1144459 |