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Instituto de Investigação
em Vulcanologia e Avaliação de Riscos
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Painéis ► em encontros internacionais

 

Referência Bibliográfica


ALATORRE-IBARGUENGOITIA, M.A., DELGADO-GRANADOS, H., KUEPPERS, U., DINGWELL, D.B. (2007) - Release of kinetic energy during explosive events at Popocatépetl Volcano (Mexico): constraints from fragmentation experiments. AGU Joint Assembly, Acapulco, México, 20 - 25 de Maio (Poster).


Resumo


The potential energy of gas overpressure in bubbles may cause magma fragmentation, creating new surface. The surplus of energy is transformed into kinetic energy for ejection of particles. The efficiency of the fragmentation process to transform the potential energy into kinetic energy during explosive eruptions is a key parameter for hazards assessment. In order to investigate the fragmentation behavior, we performed rapid decompression experiments at high temperature (850°C) using natural samples from Popocatépetl volcano, Mexico. The minimum pressure differential that leads to complete sample fragmentation (fragmentation threshold) is inversely proportional to the porosity, in accordance with previous studies (Spieler et al., 2004). Further, we used several approaches to characterize the fragmentation efficiency as a function of open porosity/ applied pressure: Grain-size distribution, surface increase, and fractal analysis. SEM images of the resulting pyroclasts show that brittle deformation dominates due to the high decompression rates. These images also show that the experimental pyroclasts have similar morphology to natural ashes from Popocatépetl volcano. On the other hand, we calculated the launching velocities of the ballistic projectiles ejected during explosive events at Popocatépetl volcano using a ballistic model considering the drag coefficient for volcanic particles. Combining both approaches (potential energy from scaled experiments and kinetic energy from the distribution of the ballistic projectiles) we constrain the exsolved volatile content and provide information on the release of kinetic energy during explosive events at Popocatépetl volcano. In this way, hazard assessment could be refined.

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