Portugal lies near the boundary between the African (Nubian) and Eurasian plates, where the two converge slowly across the Azores–Gibraltar Fracture Zone in the Atlantic. Although the mainland is far less active than the Mediterranean's plate edges, this offshore fault system can generate large, infrequent earthquakes that strike with little warning.
The most infamous was the Great Lisbon Earthquake of 1755, an estimated magnitude 8.5–9.0 event that, together with its tsunami and fires, destroyed much of the capital and reshaped European thinking about natural disasters. Genuine volcanism is confined to the Azores archipelago, a mid-Atlantic hotspot and triple junction where eruptions like Capelinhos (1957–58) on Faial continue to build and reshape the islands.