São Miguel, Azores, Portugali

Regional Level Types
São Miguel	Island
Azores	Autonomous Region
Portugal	Country

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The Archipelago of the Azores is composed of nine volcanic islands situated in the middle of the North Atlantic Ocean and is located about 1,500 km west from Lisbon and about 3,900 km east from the east coast of North America. The islands, and their economic exclusion zone, form the Autonomous Region of the Azores, one of the two autonomous regions of Portugal (the other being the Autonomous Region of Madeira).

There are nine major Azorean islands and an islet cluster, in three main groups. These are Flores and Corvo, to the west; Graciosa, Terceira, São Jorge, Pico, and Faial in the centre; and São Miguel, Santa Maria, and the Formigas Reef to the east. They extend for more than 600 km and lie in a northwest-southeast direction. The vast extent of the islands defines an immense exclusive economic zone of 1,100,000 km².

The westernmost point of this area is 3,380 km from the North American continent. All the islands have volcanic origins, although some, such as Santa Maria, have had no recorded activity since the islands were settled. Mount Pico, on the island of Pico, is the highest point in Portugal, at 2,351 m (7,713 ft). The Azores are actually some of the tallest mountains on the planet, measured from their base at the bottom of the ocean to their peaks, which thrust high above the surface of the Atlantic (Wiki).

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A geologia da ilha de São Miguel é marcada por três aparelhos vulcânicos: Fogo, Sete Cidades e Furnas. As rochas mais antigas localizam-se no extremo nordeste, com vestígios de um vulcão inactivo altamente erodido na localidade de Povoação.
S. Miguel iniciou a sua formação há 4,1 M. a. e foi sendo sucessivamente aumentada pelo material expelido em novas erupções.
A actividade vulcânica mais recente encontra-se na parte Este da ilha (Sete Cidades e Picos). Neste sector existem depósitos de piroclastos basálticos. A caldeira das Sete Cidades ter-se-á formado há aproximadamente 16.000 anos, com 17 erupções nos últimos 5.000 anos. No interior da cratera, e devido à presença de água, as erupções foram explosivas, enquanto que nas vertentes exteriores apresentaram estilo havaiano-estromboliano.
O vulcão do Fogo, na parte central, apresenta uma caldeira com 3,25 km de diâmetro, com um lago no seu centro. Nos flancos do vulcão existem extensos depósitos de piroclastos. As rochas mais antigas desta região possuem uma idade absoluta de 280.000±140.000 anos, tendo-se formado em ambiente submarino. Após duas erupções importantes verificou-se o abatimento da estrutura e a formação de uma caldeira há 46.500 e 26.500 anos. Nos últimos 40.000 anos a actividade tornou-se mais explosiva ocorrendo dentro da caldeira. Nos últimos 15.000 anos há o registo de 20 erupções, com dois registos históricos (1953 e 1954), sempre de carácter explosivo ao nível da cratera. Em 1563, uma erupção explosiva (subpliniana), com emissão de lava, soterrou parte da povoação de Ribeira Seca.
O vulcão das Furnas encontra-se perto da região nordeste e a sua caldeira (5 km de diâmetro) ter-se-á formado há 12.000-10.000 anos. É o vulcão mais recente e estudado no contexto dos Açores, tendo ocorrido alguns episódios vulcânicos curtos nos últimos 5.000 anos (dois históricos), de carácter explosivo (pliniano a subpliniano). Em 1630, uma erupção com formação de escoadas piroclásticas terá morto 195 pessoas na ilha.
Ref: OLIVEIRA, Óscar et al - Desafios Geologia 10, vol 1, Edições ASA, Lisboa, 2009.

Geology translated from above:
The geology of the island of São Miguel is marked by three volcanic centres: Fogo, Sete Cidades and Furnas. The oldest rocks are located in the extreme northeast, with traces of a highly eroded inactive volcano in the town of Povoação. S. Miguel began its formation 4.1 million years ago and was successively enlarged by material expelled in subsequent eruptions. The most recent volcanic activity is found in the eastern part of the island (Sete Cidades and Picos). In this sector there are deposits of basaltic pyroclasts. The Sete Cidades caldera was formed approximately 16,000 years ago, with 17 eruptions in the last 5,000 years. Inside the crater, and due to the presence of water, the eruptions were explosive, while on the outer slopes they were Hawaiian in style - strombolian. The Fogo volcano, in the central part, has a caldera 3.25 km in diameter, with a lake in its center.On the flanks of the volcano there are extensive deposits of pyroclasts. The oldest rocks in this region have an absolute age 280,000±140,000 years ago, having been formed in a submarine environment. After two major eruptions, the structure collapsed and a caldera was formed between 46,500 and 26,500 years ago. In the last 40,000 years, activity has become more explosive, occurring within the caldera. In the last 15,000 years there have been 20 recorded eruptions, with two historical records (1953 and 1954), always of an explosive nature at the level of the crater. In 1563, an explosive eruption (subplinian), with lava emission, buried part from the village of Ribeira Seca. The Furnas volcano is located near the northeast region and its caldera (5 km in diameter) was formed 12,000-10,000 years ago. It is the most recent volcano studied in the context of the Azores , with some short volcanic episodes having occurred in the last 5,000 years (two historic ones), of an explosive nature (Plinian to sub-Plinian). In 1630, an eruption with the formation of pyroclastic flows killed 195 people on the island. Ref: OLIVEIRA, Óscar et al - Challenges Geology 10, vol 1, Edições ASA, Lisbon, 2009.

Mineral List

Mineral list contains entries from the region specified including sub-localities

93 valid minerals. 4 (TL) - type locality of valid minerals. 1 erroneous literature entry.

Rock Types Recorded

Rock list contains entries from the region specified including sub-localities