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Instituto de Investigação
em Vulcanologia e Avaliação de Riscos
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Referência Bibliográfica

QUEIROZ, G., GASPAR, J.L. (1998) - The geological setting of the Azores archipelago: a review. InterRidge Workshop: Long term monitoring of the Mid-Atlantic Ridge (MOMAR). Lisboa, Museu da Ciência, Outubro (Comunicação Oral).


The Azores islands, located between the latitudes 37°- 40º E and longitudes 25°- 31° W, rise from the so-called Azores platform, a deeply irregular submarine area limited by the 2000 meters bathymetric line.
The tectonic setting of the region is dominated by the Azores triple junction, a point where the American, Eurasian and African lithospheric plates meet. The Mid-Atlantic Ridge, the East Azores Fracture Zone, the Terceira Rift (including the S. Miguel-Terceira-Graciosa, Faial-Pico and S. Jorge alignments) and the Gloria Fault are the most important fracture systems in this sector of the North Atlantic but the way how they interact is not yet well understood. In fact, if the limit between the American Plate at W and the Eurasian and African plates at E is well established by the Mid-Atlantic Ridge, the nature and exact location of the boundary between the Eurasian and African plates is still doubtful. Based on geological and geophysical data several geodynamic models exist to characterise the evolution of the Azores triple junction and the seismovolcanic activity in the area.
Due to the peculiar geologic setting of the Azores seismic and volcanic phenomena are frequent. Historical records mention that since the settlement of S. Miguel island, sometime between 1439 and 1443 A.D., strong earthquakes, various seismic crises and about 25 volcanic eruptions occurred in the Azores region being sometimes responsible for many deaths and extensive destruction. The last catastrophic event happened last July when a 5.8 magnitude earthquake was provoked 9 deaths and severe damages on Faial, Pico and S. Jorge islands.
Presently the volcanic activity is evident in various fields of diffuse degassing, fumaroles and thermal springs, either subaerial or submarine and preferential1y placed along NW -SE trends between the Mid-Atlantic Ridge and S. Miguel Island.