The Picos Volcanic Fissural System () is a system of

scoria cone A cinder cone or scoria cone is a steep, conical landform of loose pyroclastic fragments, such as volcanic ash, clinkers, or scoria that has been built around a volcanic vent. The pyroclastic fragments are formed by explosive eruptions or l ...

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 ( , ; ) 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 seven Aeolian Islands, a volcanic arc north of Sicily, and the mytho ...

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 Plinian eruptions or Vesuvian eruptions are volcanic eruptions characterized by their similarity to the eruption of Mount Vesuvius in 79 AD, which destroyed the ancient Roman cities of Herculaneum and Pompeii. The eruption was described in a le ...

centring on the volcano of

Água de Pau Água de Pau is a Freguesia (Portugal), civil parish in the concelho, municipality of Lagoa (Azores), Lagoa in the Portugal, Portuguese archipelago of the Azores. The population in 2011 was 3,058, in an area of 17.46 km2. It contains the lo ...

. 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 eruption A Vulcanian eruption is a type of volcanic eruption characterized by a dense cloud of ash-laden gas exploding from the crater and rising high above the peak. They usually commence with phreatomagmatic eruptions which can be extremely noisy due t ...

s, 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 stratovolcano, stratovolcanic complex, located in the central part of the island of São Miguel Island, São Miguel, in the Portugal, Portuguese archipelago of the Azores. More recognizable for the Lagoa do Fogo at its ce ...

, 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 extremely vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicula ...

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 ...

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 * * * * {{Authority control Geology of the Azores São Miguel Island