The archipelagos of Madeira and the Azores are scattered within the Atlantic Ocean: the Azores straddling the Mid-Atlantic Ridge on a tectonic triple junction, and Madeira along a range formed by in-plate hotspot geology. Geologically, these islands were formed by volcanic and seismic events. The last terrestrial volcanic eruption occurred in 1957–58 (Capelinhos) and minor earthquakes occur sporadically, usually of low intensity.