Picos Fissural Volcanic System

Nearly 200 scoria cones of the Picos volcanic system dot the narrow central zone of Sao Miguel Island between Sete Cidades and Agua de Pau volcanoes. This area of monogenetic fissure-controlled, dominantly basaltic volcanism, much of which post-dates the roughly 5,000-year-old Fogo eruption, cannot be assigned to either volcano and appears related to en-echelon fissures overlying a fracture zone. Thick pumice deposits thought to originate from the Picos system may have originated from vents or a caldera destroyed and now buried by young basaltic volcanism.

The most noteworthy of the young vents is Serra Gorda, SE of Siete Cidades, and the cone that produced a lava delta south of Agua de Paul village. The majority of the inhabitants of Sao Miguel Island occupy both coasts below this volcanic zone. At least 18 eruptions have occurred during the past 2,800 years, although the only recorded eruption occurred in 1652 CE.

The most recent activity has been basaltic; however, two more-explosive trachytic eruptions occurred during the past 1,100 years.