From the standpoint of plate tectonics, the ongoing northward drive of the African plate into the Eurasian plate in the Mediterranean basin is the most prominent aspect of the European scene today. The pressure exerted by the African plate is the overall cause of the rise of the Pyrenees, the Alps and the Carpathian mountains. Limestones and other sediments, the ancient floor of the Tethys Sea, are pushed high and now make up much of these ranges. A submarine back-arc basin develops south of Italy, which is one of several Mediterranean mini-continental fragments caught between the two plates. This buckling of the Earth's crust forces up Italy's mountains and stimulates active faults and volcanoes such as Mount Etna. Iberia, another separate terrain unit, has been rotated and emplaced against the rest of Europe by the plate collision.