The oldest volcano of the island is the Nordeste shield volcano, a highly eroded edifice in the easternmost region of the island and its age ranges from 4 Ma to 0.95 (Fernandez, 1982). Thereafter, volcanic activity evolved westwards, forming the remaining volcanic complexes of São Miguel, with Picos complex being the most recent, corresponding to an area dominated by basaltic volcanism, characterized by numerous scoria cones, frequently aligned along fractures trending WNW–ESE and NW–SE. The NW–SE trend corresponds to the orientation of the so-called Terceira Rift, a regional leaky transform fault defined since Machado (1959)