Excursion guide for field trip V1 : 'Island of São Miguel'

• Autor(a) principal: Martins, J. Ávila
• Data de Publicação: 1982
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Texto Completo: http://hdl.handle.net/10400.3/4885
• topic: Volcanism; São Miguel Island (Azores); Azores Archipelago

S. Miguel, the largest islands of the archipelago (757 km2), consists of four volcanoes with summit calderas, from W toward E: Sete Cidades, Água de Pau, Furnas and Povoação. The range formed by the latter three volcanoes rises to the height of 1105 meters (in Pico da Vara) and trends approximately E-W, but the massif of Sete Cidades, separated from the eastern area by a low narrow zone - «Região dos Picos» - formed by recent basalts, is oriented according to the regional trend, i.e., approximately WSW-ESE. That Sete Cidades trend controlled by fracture alignment supported by the linear positions of the recorded submarine eruptions, parallel to the SW coast of the island. From field relationship and some available radiometric data, it is possible to establish the following -eruptive sequence (Zbyszewski, 1974) : Nordeste basalt complex (4 m.y.) , trachytes of Povoação, Furnas and Água de Pau, with intercalations of basaltic eruptions, basalts of Sete Cidades and Picos, and the historic recorded eruptions which were trachytic (explosive) and basaltic (effusive). […].