The Picos Volcanic Fissural System ( pt, Sistema Vulcânico Fissural dos Picos) is a system of

scoria cone Scoria is a pyroclastic, highly vesicular, dark-colored volcanic rock that was ejected from a volcano as a molten blob and cooled in the air to form discrete grains or clasts.Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, eds. (2005) ''G ...

s that build up the central region of the island of São Miguel (between Sete Cidades and Água de Pau volcanoes). This volcano is very young with most of it only 5000 years old. The only recorded eruption was in 1652, but seven other eruptions have taken place in the cinder cone group in the last 10,000 years.

History

This volcanic system is the most recently formed on the island of São Miguel, with its eruptive history dominated by Hawaiian, basaltic and

Stromboli Stromboli ( , ; scn, Struògnuli ) is an island in the Tyrrhenian Sea, off the north coast of Sicily, containing Mount Stromboli, one of the four active volcanoes in Italy. It is one of the eight Aeolian Islands, a volcanic arc north of Sici ...

phases. In the last 5000 years, there have been approximately 30 eruptions, with the most recent events occurring with recorded human history. The first, in 1563, succeeded a Phreato plinian eruption centring on the volcano of

Água de Pau Água de Pau is a civil parish in the municipality of Lagoa in the Portuguese archipelago of the Azores. The population in 2011 was 3,058, in an area of 17.46 km². It contains the localities Água de Pau, Caloura, Cerco, Cinzeiro, Galera an ...

. During this 1563 eruption, known as the Pico do Sapateiro or Queimado, basalt lava flows reached as far as Ribeira Seca, in the north coast.A. Gomes (2013) The second eruption, which started on 19 October 1652, resulted in the formation of three Trachyte domes and involved explosive phases of Vulcanian eruptions, by the time the eruptions end on 26 October 1652. This, more recent eruption, was a markedly eruptive/explosive event, composed of evolved magma that generally does not characterize the Picos region.

Geography

The Picos fissural system is located in the central-western part of the island of São Miguel, delimited in the south-east by the caldera/massif of Sete Cidades and on the east by the

Água de Pau Massif Água de Pau Massif is a stratovolcanic complex, located in central part of the island of São Miguel, in the Portuguese archipelago of the Azores. More recognizable for the Lagoa do Fogo at its centre, the volcanic complex includes centuries o ...

, running approximately and extending to north and southern coasts. The landscape is dominated by the presence of approximately 300 monogenic cones, composed of scoria and lava flows. Similarly, the area is punctuated by

maar A maar is a broad, low-relief volcanic crater caused by a phreatomagmatic eruption (an explosion which occurs when groundwater comes into contact with hot lava or magma). A maar characteristically fills with water to form a relatively shallow ...

pumice Pumice (), called pumicite in its powdered or dust form, is a volcanic rock that consists of highly vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicular vol ...

cones and

lava dome In volcanology, a lava dome is a circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions on ...

s, in particular in the transitional zones between the adjacent central volcanoes. The volcanostratigraphy of magmas/lava flows of the region include deposits between 2200 and 2800 years B.C., while radiometric deposits from the principal areas of population (Ponta Delgada) are from 12300 B.C.

References

;Notes ;Sources * * * * {{citation , last=Gomes , first=A. , year=2013 , title=História eruptiva do Sistema Fissural dos Picos e avaliação da susceptibilidade a escoadas lávicas (Ilha de S. Miguel, Açores). Dissertação de doutoramento no Ramo de Geologia, especialidade Vulcanologia , publisher=Departamento de Geociências/University of the Azores , pages=352 , language=Portuguese Geology of the Azores São Miguel Island