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


Referência Bibliográfica

SCHEU, B., KUEPPERS, U., SPIELER, O., DINGWELL, D. (2007) - Determination of surface area of silicic magma. Cities on Volcanoes 5 conference, Shimabara, Japão, 19 - 23 de Novembro (Poster).


Measurement of the surface area of volcanic products is still quite rare in the field of volcanology and mostly restricted to ash samples. The surface area of rock samples is supposed to react much more sensitive to cracks and fractures, as for instance the porosity, especially in the case of moderate to highly porous samples. Thus the surface area may allow shedding light on late-stage processes during emplacement and cooling of silicate melts. In this context, it has to be distinguished between the primary surface of a rock and secondary processes affecting this value. Thermal cracking, fragmentation, and secondary mineralization lead to increased values of the surface area. This yields important information on the strength as well as alteration of the natural material and its behavior in a stress field.


Based on gas sorption theory, we analyzed the surface area of volcanic products from Unzen Volcano and Montserrat. Entire rock cylinders as well as pyroclasts generated during rapid decompression experiments and natural ash samples were measured following the multipoint method of Brunauer-Emmett-Teller (BET). With the estimated surface area increase and the fracture-surface energy of silicic rocks from literature we are able to quantify the amount of energy consumed to create new surface during a fragmentation event to be in the order of a few percent.