The Alboran domain, the seafloor beneath the Alboran Sea (known as the internal zones) together with the surrounding mountains (known as the external zones; the Gibraltar Arc and Atlas Mountains), is mostly made of continental crust and marks the western-most terminus of the terranes that were subducted between the African and Eurasian Plates when the Tethys Ocean closed. Reoccurring earthquakes at a depth of about indicates that this subduction is ongoing and that complex interactions between the lithosphere and mantle are forming the region. The internal zones are made of Late Paleozoic to Triassic rocks that were piled up during the Tertiary and has been extended since the Early Miocene.