HR: 0800h
AN: V31E-0709    [Abstracts]
TI: Revising Methods for Moisture Removal in Tephra Bulk Samples
AU: * Parada, J M
EM: parajm13@mail.buffalostate.edu
AF: SUNY College at Buffalo, Dept. of Earth Sciences and Science Education 1300 Elmwood Ave., Buffalo, NY 14222, 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 14222, United States
AB: The current standard for removing water content from tephra seems inefficiently long. Tephra, depending on composition, can be porous and requires less time than other rocks and soil to dry. The Standard Test Method for Laboratory Determination of Water (ASTM D 2216-98) content of soil and rock by mass is not accurate specific to tephra bulk samples. A study was conducted to provide valuable information on drying dynamics to aid a possible new guideline specific to this type of material. The pyroclastic material used for this study was taken in the summer of 2006 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). Tephra bulk samples from two eruptions, Obsidian Flow and Deadman Creek near Mammoth, California were tested in the lab. Both samples were the result of rhyolitic eruptions composed of pumice, obsidian, and other lithics. Particle size ranges from .01 mm to 4.0 mm. It was found after testing the existing standard (24h) that tephra bulk samples require much less time to dry in an oven than suggested. Maximum drying time in the oven was 6 hours, and as little as 5 hours for smaller samples. However, the drying time depends on the amount of water content the samples retained before being placed in an oven and the mass of the sample. It seemed that soaking the samples for a control experiment over night were more comparable to the samples that are freshly taken in the field. Samples that were just wetted with a defined amount of water and stirred before drying dried up in less than one hour. After experimenting in the lab with drying tephra samples, it was concluded that the current standard was not accurate for tephra bulk samples. They required much less time than were stated, only 5-6 hours compared to 16-24 hours. Samples were baked at 150 degrees centigrade until all water content was evaporated, as the mass of the samples was measured every 30 minutes and compared to pre-drying humidified mass of the tephra we started with.
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