HR: 0800h
AN: V31E-0708    [Abstracts]
TI: Effect of Particle Size on Tephra Sample Drying
AU: * Lannan, A
EM: aplannan2gmail.com
AF: SUNY College at Buffalo, Dept. of Earth Sciences and Science Education 1300 Elmwood Ave., Buffalo, NY 14226, United States
AU: Martinez-Hackert, B
EM: martinb@buffalostate.edu
AF: SUNY College at Buffalo, Dept. of Earth Sciences and Science Education 1300 Elmwood Ave., Buffalo, NY 14226, United States
AU: Kobs, S
EM: sekobs@buffalo.edu
AF: SUNY at Buffalo, Dept. of Geology 876 Natural Sciences Complex, Buffalo, NY 14260, United States
AB: The analysis of excavated tephra and other pyroclastic material often includes the removal of environmental moisture that has migrated into the individual clasts subsequent to their deposition. Elimination of the moisture content of a sample allows researchers to gather quantitative data concerning the mass, density, and particle size of the ejecta at the time of the eruptive event. Progress in the modeling of past eruptions using stratigraphic evidence has increased interest in this type of data. Many of the formulae used in the modeling of ash fall from volcanic events include variables for the density and particle size (Carey and Sparks 1986) of the ejected material. Hence, the first step of data processing in the laboratory is drying of the tephra and proceeding to a particle size analysis. While standards for the removal of moisture from soil and rock samples exist for use in the geotechnical and construction fields (ASTM D 2216-98), no methodological guidelines have been created for use in the field of volcanology. The method described in ASTM D 2216-98, in which samples are baked at a standard temperature of 110° C until they reach a constant mass, is similar to that used by researchers studying tephra. However, lack of access to the exact apparatus specified by ASTM D 2216-98 in many volcanology and geophysics labs, as well as the fact that it is not specifically concerned with pyroclastic material, may prohibit acceptance of this standard by researchers. This paper provides information that may assist in the construction of a future standard of drying volcanic ash fall deposits. We tested whether the location of moisture within the bulk tephra sample is affected by particle size and what effect the unequal distribution of moisture between different sized particles has on drying times. The pyroclastic material used for this study was taken in the summer of 2007 from the Inyo Crater area of California. The tephra was deposited by a series of Plinian and sub-Plinian eruptions approximately 550 years ago (Miller 1985). It is composed of mostly pumice, with smaller amounts of lithics and glass. Samples were sieved in their naturally humid stage and immediately dried as individual particle size dependent groups to a constant mass in the laboratory at 150 degrees centigrade. The weight of the groups was taken every 30 minutes during drying. As a control, each of the dry groups was weighed and moisture was added until it increased the sample's mass by 10 percent. The samples were then re-dried with measurements again being taken at 30-minute intervals. Preliminary results indicate that large pumice particles contain a disproportionate amount of the deposits moisture.
DE: 5194 Instruments and techniques
DE: 5480 Volcanism (6063, 8148, 8450)
DE: 8429 Lava rheology and morphology
DE: 8455 Tephrochronology (1145)
DE: 8494 Instruments and techniques
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting