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Instituto de Investigação
em Vulcanologia e Avaliação de Riscos
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Referência Bibliográfica

PACHECO, J.M. (2004) - The caldera-forming event of Faial island central volcano. IAVCEI General Assembly, Pucon, México, Novembro (Comunicação Oral).​


Faial Island is located to the east of the Mid-Atlantic Ridge and is part of the Azores archipelago. Two main active volcanic systems can be recognized in the island: a major central volcano with a maximum height of 1,043 metres, truncated by a summit caldera with a diameter of about 2 km and a WNW-ESE basaltic fissural system that extends along the western flank of the central volcano into the sea.
About 16,000 years ago the central volcano activity changed dramatically from a basaltic, mainly effusive, volcanism to a trachytic explosive activity. Since then 14 explosive eruptions were produced, 9 of them on the last 2,000 years. The largest of those eruptions occurred about 1,000 years ago and was associated to the event that formed the present caldera. During this event the caldera formation unfolded in two stages. One first phase produced mostly lithic rich surges and a small pumice fall deposit, both dispersed mainly towards the north. The second phase was dominated by the extrusion of a pyroclastic flow, dispersed towards the east, along the depression of Pedro Miguel graben.
The present caldera is excentric relative to the central volcano, and is nested in the well-developed Pedro Miguel graben suggesting that, besides the volcanic processes, the tectonic setting was also an important factor controlling the caldera formation.