Resumo

BRENES, José. Application of sequential fragmentation/Transport theory to deposits of 1723 and 1963-65 eruptions of Irazú Volcano, Costa Rica: Negative dispersion case. Rev. Geol. Amér. Central [online]. 2013, n.48, pp.63-85. ISSN 0256-7024.

Sequential fragmentation/transport theory (SFT) was used to analyze tephra deposits of the two main recent explosive eruptions from Irazú volcano, the 1723 and 1963-65 events. The final results provide a new way to analyze fragmentation and transport processes, which fix well with the field observations made by Alvarado (1993). A new way to process fragmentation/transport revealed 4 phi ranges that can be associated to initial volcanic fragmentation. The SFT fragmentation coefficient method is expanded to include all 5 subpopulations, allowing to compare the 1723 and 1963-65 events. SFT interpretation of 1723 eruptions is in good agreement with the volcanological description of such explosive events, whereas SFT points to a more complex 1963-65 eruption, probably due to volcanic recycling and sedimentary reworking as it is observed in the field.

Palavras-chave : Sequential fragmentation/transport; 1723 and 1963-65eruptive units; Irazú volcano; Costa Rica; Volcanic Explosivity Index.

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