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Artigos em revistas ► internacionais com arbitragem

 

Referência Bibliográfica


PIMENTEL, A., PACHECO, J., SELF, S. (2015) - The ~1000-years BP explosive eruption of Caldeira Volcano (Faial, Azores): the first stage of incremental caldera formation. Bulletin of Volcanology, 77:42. doi: 10.1007/s00445-015-0930-2

Resumo


​The ∼1000-years BP eruption ofCaldeira Volcano (Faial Island) was one of the last major explosive events re- corded in the Azores. It produced a complex succession of pyroclastic deposits, known as the C11, divided into three members. At the base is the Brejo Member, a sequence of fine- to coarse-grained parallel-bedded ash layers found in the NW sector of the island. The middle part corresponds to the Inverno Member, a coarse-grained massive pumice fall deposit, restricted to the north flank of Caldeira Volcano. The top is dominated by the Cedros Member which includes massive to diffuse-stratified lapilli-ash and lithic breccias, ex- posed along the north and east flanks of the volcano. A min- imum bulk volume ofat least 0.22 km3 (>0.1 km3 dense rock equivalent (DRE)) is estimated for the C11 eruption, although a large portion may have been deposited offshore. The juve- nile products are trachytic (59 wt% SiO2) with a homogenous whole-rock composition and mineral assemblage throughout the pyroclastic succession. However, petrographic and groundmass glass analyses indicate magma mingling/mixing processes between two trachytic batches. The C11 eruption history is divided into three phases (following the member division) with distinct eruptive styles: (1) an initial phreatomagmatic phase caused by rising magma (∼950 °C) encountering a crater pond or aquifer, (2) a fall-dominated phase which established a sub-Plinian column up to 14 km high (mass eruption rate (MER) of 1.2×107 kg/s) and (3) prolonged pyroclastic fountaining and sustained quasi-steady pyroclastic density current generation followed by summit collapse. The C11 eruption is interpreted as the first stage in the formation of an incremental caldera. This study provides valuable insights for a better understanding ofsmall but com- plex explosive eruptions and their impact on ocean islands.
 

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Anexos