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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., LINARES-LÓPEZ, C. (2007) - Fragmentation threshold and fragmentation eficiency of samples from Popocatépetl Volcano: an experimental study. El Chichón Volcano: Twenty five years later. A commemorative conference, San Cristobal de las Casas, México, 20 - 25 de Março (Poster).


Laboratory experimentation is becoming an increasing important feature within volcanic research, as experiments are used to explore novel phenomena that are not accessible to direct observations and to provide systematic observation of processes. In a laboratory experiment, the process can be repeated at fixed conditions and the known starting conditions can be correlated with the results. In particular, the design and development of fragmentation bomb technology Alidibirov and Dingwell, 1994), has provided volcanology with the capability of controlled and systematic analysis of the fragmentation behavior of magma upon rapid decompression. We performed fragmentation experiments at high temperature (850°C) using natural samples from Popocatépetl volcano in order to measure the minimum overpressure required to completely fragment magma (fragmentation threshold). The results show a close relationship between the fragmentation threshold and the open porosity of the samples, accordance to previous studies of several volcanoes Spieler et al., 2004). SEM images performed on the resulting pyroclasts shows that brittle deformation dominates due to the high decompression rates. These images also show that the experimental pyroclasts have similar morphology to natural pyroclasts from Popocatépetl volcano. We also analyzed the grain-size distribution of the experimental pyroclasts. The results show a non-Gaussian distribution where the mean diameter depends on the applied pressure (ΔP) and open porosity of the samples (Φ). Further, fractal analysis using cumulative weight fractions shows a linear relationship between the fractal dimension and the potential energy for fragmentation (PEF=ΔP*Φ) here the slope depends on the open porosity of the sample. We compared the grain-size distribution of the experimental pyroclasts with ash-fall deposits of recent explosions of Popocatépetl volcano.