Alps Vs. Apennines

The comparison between Alps and Apennines shows they are orogens with distinct characters both in terms of geological and geophysical data. They have respectively 1) convergence rate faster than the slab retreat vs. convergence rate slower than the slab retreat; 2) double vs. single vergence; 3) high vs. low morphological and structural elevation; 4) deep vs. shallow rocks involved; 5) the occurrence of higher metamorphic degree vs. lower metamorphic degree; 6) the basal decollement involves the crust and the LID of both upper and lower plates whereas only the shallow crust of the lower plate contributes to the accretionary prism; 7) shallow vs. deep foredeep; 8) low vs. high dip of the foreland monocline; 9) thickened vs. thinned crust under the ridge; 10) the Alps have both in the upper and in the lower plate a pre-subduction Moho, whereas the Apennines have in the footwall plate a pre-subduction Moho, but in the hangingwall they present a new forming Moho; 11) thickened lithosphere vs. a shallow asthenosphere in the hangingwall; 12) no vs. well developed backarc basin and related alkaline-tholeiitic magmatism; 13) scarce vs. larger abundance of subduction-related volcanism; 14) smooth vs. high amplitude gravity and heath flow anomalies. The two belts interfered since the southern prolongation of the Alps has been incorporated into the internal Apennines, and the Apennines slab retreat is subsiding much part of the Alps, partly counteracting their uplift. These differences mimic worldwide asymmetries as the eastern vs. western Pacific (i.e., Andes vs. Marianas) or Himalayas vs. Barbados subduction zones, and favor a global scale explanation such as the "westward" drift of the lithosphere rather than regional slab-pull related variations in the tectonic style.