HR: 1400h
AN: V33B-06    [Abstracts]
TI: Glacial fragmentation induced by eruptive activity: Popocatépetl Volcano (México)
AU: * Julio-Miranda, P
EM: patricia.julio@uaslp.mx
AF: Cuerpo Académico de Ciencias Sociales, CCSyH, Universidad Autónoma de San Luis Potosí, Av. Industrias 101-A, Frac. Talleres, SLP, SLP 78494, Mexico
AU: Delgado-Granados, H
EM: hugo@geofisica.unam.mx
AF: Instituto de Geofísica, Universidad Nacional Autónoma de México, C.U., Coyoacán, Mexico, DF 04510, Mexico
AB: Ice-volcano interactions at volcanoes depend on eruptive behavior, glacier characteristics and time scales. High- intensity eruptions occurred in a short span of time can provoke dramatic glacial changes whilst intermittent eruptive behavior of variable intensity over years can generate gradual glacial changes. Popocatépetl volcano hosted a small glacial area when it started to erupt in December 1994. Over 12 years of intermittent and fluctuating eruptive activity gradual glacial changes occurred. Based on results obtained by digital photogrammetry using a collection of aerial photographs, daily eruptive activity reports and observations a model of glacial evolution is proposed. 1) Adjust phase, no important volume loss occurred in spite of intense eruptive activity, although upheaval at the terminus was observed. 2) Thinning phase, through 1999 the glacier experienced considerable thinning due to differential ablation due to the irregular distribution of the pyroclastic material deposited on its irregular glacial surface with stair-like pattern. Flows and rilling-related to tephra remobilization incised the glacier surface repeatedly. 3) Areal retreat phase, the greatest glacial area loss occurred in 2000 and some elongated blocks of ice were identified. 4) Fragmentation phase, started on 2001, as a combination of differential ablation and recurrence of remobilization processes of tephra reduced the glacier to a set of blocks, the upper part of them was covered by a thick layer of tephra and their sides exposed the remnant ice to ablation processes. Ever since isolated blocks are spread over the pre-eruptive glacial area. Glacier evolution was fundamentally influenced by the fluctuating eruptive behavior over the years but was not the single factor.
DE: 8404 Volcanoclastic deposits
SC: Volcanology, Geochemistry, and Petrology [V]
MN: 2007 Joint Assembly