The Terceira Rift is a system of fractures that extends from the Mid-Atlantic Ridge to the Glória Fault that represents the main frontier between the Eurasian and African Plates. It is defined by a line of submarine volcanoes and island mounts that extend northwest to southeast for about , from the area west of Graciosa until the islets of the Formigas, that includes the islands of Graciosa, Terceira and São Miguel. Its northwest limit connects to the Mid-Atlantic Ridge, while the southeast section intersects the Gloria Fault southeast of the island of Santa Maria.