This supplies the area with huge amounts of heat and a reduction in pressure that melts rock from the asthenosphere (or upper mantle) beneath the rift area, forming large flood basalt or lava flows. Divergent boundaries also form volcanic islands, which occur when the plates move apart to produce gaps that magma rises to fill.Ĭurrent research indicates that complex convection within the Earth's mantle allows material to rise to the base of the lithosphere beneath each divergent plate boundary. Most active divergent plate boundaries occur between oceanic plates and exist as mid-oceanic ridges. Divergent boundaries within continents initially produce rifts, which eventually become rift valleys. In plate tectonics, a divergent boundary or divergent plate boundary (also known as a constructive boundary or an extensional boundary) is a linear feature that exists between two tectonic plates that are moving away from each other. In an extreme and approximate synthesis, the evolution of the western Mediterranean is inferred to follow a Wilson Cycle (at a small scale) with the following main steps : (1) northward Nubian subduction with Mediterranean back-arc extension (since ~35 Ma) (2) progressive cessation, from west to east, of Nubian main subduction (since ~15 Ma) (3) progressive onset of compression, from west to east, in the former back-arc domain and consequent basin inversion (since ~8–10 Ma) (4) possible future subduction of former back-arc basins.Continental-continental divergent/constructive boundary These features prevent, at present, the development of long and continuous thrust faults. The tectonic reorganization of the Nubia-Eurasia boundary in the study area is still strongly controlled by the inherited tectonic fabric and rheological attributes, which are strongly heterogeneous along the boundary. Part of the contractional deformation may have shifted toward the north in the Liguro-Provençal basin possibly because of its weak rheological properties compared with those of the area between Tunisia and Sardinia, where no oceanic crust occurs and seismic deformation is absent or limited. It follows that basin inversion is rather advanced on the Algerian margin, where a new southward subduction seems to be in its very infant stage, while it has still to really start in the Tyrrhenian margin, where contraction has resumed at the rear of the fold-thrust belt and may soon invert the Marsili oceanic basin. 2 Ma) basins following a similar propagation of the cessation of the subduction, i.e., older to the west and younger to the east. Onset of compression and basin inversion has propagated in a scissor-like manner from the Alboran (c. Between northern Morocco, to the west, and northern Sicily, to the east, contractional deformation has shifted from the former subduction zone to the margins of the two back-arc oceanic basins (Algerian-Liguro-Provençal and Tyrrhenian basins) and it is now mainly active in the south-Tyrrhenian (northern Sicily), northern Liguro-Provençal, Algerian, and Alboran (partly) margins. Previously-published tectonic, seismological, geodetic, tomographic, and seismic reflection data (integrated by some new GPS velocity data) are reviewed to understand the reorganization of the convergent boundary in the western Mediterranean. With the progression of Nubia-Eurasia convergence, a tectonic reorganization is therefore necessary to accommodate future contraction.

In the western Mediterranean area, after a long period (late Paleogene-Neogene) of Nubian (W-Africa) northward subduction beneath Eurasia, subduction has almost ceased, as well as convergence accommodation in the subduction zone.

Convergent boundary