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Instituto de Investigação
em Vulcanologia e Avaliação de Riscos
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Referência Bibliográfica

GASPAR, J.L., BARRIGA, F., MIRANDA, M., QUEIROZ, G., PACHECO, J.M., FERREIRA, T., MADEIRA, J., WALLENSTEIN, N., COUTINHO, R., ALMEIDA, M.H., ANDRADE, F., EZEQUIEL, A. (2004) - The 1998-2001 Serreta Submarine Ridge volcanic eruption, W of Terceira Island:geological data from the Avila Martins oceanographic mission. IAVCEI General Assembly, Pucon, México, November (Comunicação Oral).​


On November 1998 a small seismic crisis 10 Km W of Terceira Island announced the beginning of a submarine basaltic fissure eruption, first observed by fishermen on December 18, 1998. Eruptive vents were located at depths ranging from 300 to 1000 meters along NE-SW and NW-SE tectonic trends. The event lasted for more than two years and was characterized by the discontinuous appearance of basaltic floating blocks at the sea surface. Such volcanic products, named as “lava balloons”, are closed hollow structures, spherical to ellipsoidal in shape, with a thin vesicular crust.
During the eruption several oceanographic missions were made in order to trace the submarine volcanic plumes by sonar, to locate the vents using DGPS and to sample lava balloons and ashes. In one of those missions a remote operated vehicle (ROV) was used and several dives were made above active vents located at about 400 meters depth.
The obtained images allowed to identify and characterise two different sections in the submarine volcanic plumes: a lower part, up to 200 meters high, formed by ashes, gas bubbles and lava balloons, and an upper part where ashes were absent. Furthermore it was observed that lava balloons gently ascent towards the sea surface due to their buoyant capacity.