The Mid-Atlantic Ridge is the dominant seafloor feature in the eastern Atlantic region, with a central trough and numerous transform fracture zones. Just east of the ridge, the Azores island group straddles the triple junction between the Eurasian, African, and North American plates. The islands rise from the extensive Azores Plateau, an area of thickened ocean crust. Although volcanic in origin, the oldest islands also include substantial accumulations of limestone and clay sediments. A mantle hotspot underlies the plateau and seems to be slowly spreading it apart at the Terceira Rift, a fracture that links the East Azores Fracture Zone to the Mid-Atlantic Ridge. The last volcanic eruption in the Azores was in 1957, when the Capelinhos volcano produced a cinder island (an island composed of lava fractures called cinders) off Faial’s coast.