Sete Cidades Massif is a stratovolcanic complex, referring to a polygenetic volcano and caldera, located in western part of the island of São Miguel, in the Portuguese archipelago of the Azores.

[2] These caldera collapse episodes occurred following explosive eruptions that formed the Risco, Bretanha and Santa Barbara pyroclastic fields.

A secondary phase began around 28,750 years ago and was responsible for the collapse of the northwest portion of the primitive caldera.

[3] In each of these formational phases, lapilli fallout (resulted from Plinian eruptions) and the pyroclastic flow deposits were transformed into ignimbrites, from melting.

[2] This rift zone is uncharacteristically 200 metres (660 ft) higher than the crater rim, that it could shield Ponta Delgada from all but pyrcolastic flows associated with any future eruption.

[2] The northwestern flank is marked by the Mosteiros Graben, a tectonic structure aligned in a northwest to southeast orientation following the fault of the Terceira Rift zone.