Picos Fissural Volcanic System

Geography & Climate

Picos Fissural Volcanic System is located in Portugal, within the Azores-Terceira Rift Volcanic Province of the broader Atlantic Ocean Volcanic Regions. Situated at 37.78° N, 25.67° W in the Northern Hemisphere, the volcano lies within a temperate climate zone. At just 350 meters above sea level, Picos Fissural Volcanic System is a relatively low-elevation volcanic feature. Despite its modest height, it remains an active geological formation with the same underlying magmatic processes as its taller counterparts. The volcanic landform is characterized as a cluster, which describes the physical shape and structure of the volcanic edifice as observed from the surface.

Geological Context

Picos Fissural Volcanic System is situated along a rift zone, where tectonic plates are pulling apart. As the crust thins and fractures, magma rises to fill the gap, creating volcanic activity. Rift volcanism typically produces more fluid lava flows rather than explosive blasts, which means communities near Picos Fissural Volcanic System in Portugal generally face slower-moving hazards like lava flows and ground fissures rather than sudden pyroclastic events. However, rift volcanoes can still generate significant ash emissions and gas releases that affect local air quality. The dominant rock type is trachybasalt / tephrite basanite, a dark, fine-grained volcanic rock that forms from rapidly cooling, low-viscosity lava. Basaltic eruptions tend to be less explosive and produce fluid lava flows that can travel long distances. While less immediately dangerous than explosive eruptions, basaltic lava flows can destroy structures and infrastructure in their path, and volcanic gases released during these eruptions can affect air quality over a wide area.

Eruption History Summary

Picos Fissural Volcanic System has 7 recorded eruptions in the geological database, spanning from 4040 BCE to 1652 CE. The most powerful recorded event was an explosive event producing ash plumes up to several kilometers in 1652 CE, reaching VEI 2 on the Volcanic Explosivity Index. This eruption frequency indicates a moderately active volcanic system with periodic reawakenings.

Significance

With 7 recorded eruptions on file, Picos Fissural Volcanic System has enough documented activity to help scientists identify patterns in its eruptive behavior.

GVP Reference Summary

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.

— Smithsonian Institution, Global Volcanism Program