The principal tectonic structures that exist in the region of the Azores are the Mid-Atlantic Ridge, the Terceira Rift, the Azores Fracture Zone and the Glória Fault. The Mid-Atlantic Ridge is the main frontier between the North American Plate and the African-Eurasian Plates that crosses the Azores Plateau between the islands of Flores and Faial from north to south then to the southwest; it is an extensive form crossed by many transform faults running perpendicular to its north–south orientation, that is seismically active and susceptible to volcanism.