HR: 1340h
AN: V53B-1545    [Abstracts]
TI: Comparing Vesicularity in Pyroclastic Deposits
AU: * Richard, D
EM: richard@min.uni-muenchen.de
AF: Earth and Environmental Sciences, LMU Munich, Theresienstr. 41/III, Munich, 80333 Germany
AU: Mueller, S
EM: mueller@min.uni-muenchen.de
AF: Earth and Environmental Sciences, LMU Munich, Theresienstr. 41/III, Munich, 80333 Germany
AU: Spieler, O
EM: spieler@min.uni-muenchen.de
AF: Earth and Environmental Sciences, LMU Munich, Theresienstr. 41/III, Munich, 80333 Germany
AU: Kueppers, U
EM: ulli@min.uni-muenchen.de
AF: Earth and Environmental Sciences, LMU Munich, Theresienstr. 41/III, Munich, 80333 Germany
AU: Scheu, B
EM: betty@min.uni-muenchen.de
AF: Earth and Environmental Sciences, LMU Munich, Theresienstr. 41/III, Munich, 80333 Germany
AU: Kramers, S
EM: simon.kremers@physik.uni-muenchen.de
AF: Earth and Environmental Sciences, LMU Munich, Theresienstr. 41/III, Munich, 80333 Germany
AU: Dingwell, D B
EM: dingwell@lmu.de
AF: Earth and Environmental Sciences, LMU Munich, Theresienstr. 41/III, Munich, 80333 Germany
AB: The investigation of processes associated with explosive volcanism requires the knowledge of the physico-chemical properties of the rock material involved. Parameters such as the rock's density and vesicularity highly influence the rheological properties as well as the fragmentation behavior of magma. Because observations inside the volcanic conduit are not possible, information on the spatial and temporal variability of the ascending magma's vesicularity is more easily obtained by measuring a statistically reliable amount of representative erupted material. In order to correlate density/porosity distributions of eruptive products with specific volcanic settings and eruption characteristics, data from six field campaigns in the circum-Pacific area were analyzed and compared. Densities from ~3000 pyroclastic- deposit samples collected on St. Augustine (Alaska), Bezymianny (Kamchatka), Unzen (Japan), Colima (Mexico), and Merapi, Krakatau and Kelut (Indonesia) were mostly measured directly in the field. This field-based density measurement method is based on the Archimedean principle whereby a sample's mass is measured in air and under water (Kueppers et al., 2005). Previous results indicated that the density peaks of St. Augustine and Bezymianny were at 1.5 and 1.6 g/cm3, respectively, whereas the most abundant densities at Mt. Unzen and Merapi were significantly higher at 2.2 and 2.3 g/cm3. However, samples collected from the 1883 Krakatau pyroclastic deposits during our most recent campaign follow a lower density distribution with a density peak of ~0.6 g/cm3. This suggests that the erupted material had a higher gas content. Results will be supported by detailed laboratory-based density and porosity measurements, and investigations of their influence on rock fragmentation and viscosity. This comprehensive work is part of the BMBF project SUNDAARC, which aims to quantify the potential risk of selected highly-explosive volcanoes by combining field and laboratory investigations.
DE: 8400 VOLCANOLOGY
DE: 8414 Eruption mechanisms and flow emplacement
DE: 8428 Explosive volcanism
DE: 8434 Magma migration and fragmentation
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005