HR: 0800h
AN: V21C-0725    [Abstracts]
TI: On 3D reconstruction of bubbles in volcanic ash particles
AU: * Proussevitch, A
EM: alex.proussevitch@unh.edu
AF: Complex Systems Research Center, Morse Hall University of New Hampshire, Durham, NH 03824, United States
AU: Sahagian, D
EM: dork.sahagian@lehigh.edu
AF: Environmental Initiative, Lehigh University, 31 Williams Dr., Bethlehem, PA 18015, United States
AU: Mulukutla, G
EM: gopal.mulukutla@unh.edu
AF: Complex Systems Research Center, Morse Hall University of New Hampshire, Durham, NH 03824, United States
AU: Kiely, C
EM: cak4@lehigh.edu
AF: Environmental Initiative, Lehigh University, 31 Williams Dr., Bethlehem, PA 18015, United States
AB: Bubbles in volcanic ash particles are primarily represented by the remnants of films and plateau borders from disrupting foam. Without preservation of complete bubbles, measuring bubble size distributions a challenging task, but one for which we have taken a novel approach. Concavities in ash particles retain a record of bubble sizes in the curvature of their concave surfaces that resulted from bubble fragmentation and quenching during energetic magma eruptions. We have used two methods to measure bubble fragment curvature on the basis of 3D reconstruction of ash particle surfaces. One is based on High Resolution X-Ray Tomography (HRXRT) and the second one is based on stereo images from tilting Scattered Electron Microscopy (SEM). Both methods allow the creation of Digital Elevation Model (DEM) datasets of the ash particle surfaces which in turn are used to identify and measure vertical cross-sectional profiles of the individual bubble fragments ("craters"). Function fit analysis for circular or elliptical functions are applied to each bubble cross sectional profile in two orthogonal directions to reconstruct sizes of the original, complete bubbles. The method allows measurement of submicron (SEM; XUM), micron or larger (HRXRT) bubbles in ash particles. The bubble size distributions so obtained can provide valuable insights regarding magma dynamics and vesiculation that lead to explosive eruptions, as well as the processes of fragmentation in eruption columns. There are no previous systematic information/databases of vesiculation metrics for explosive silicic eruptions, but this new method can be used to produce these and thus provide better insights into prehistoric eruption styles for volcanic hazard assessment.
DE: 8404 Volcanoclastic deposits
DE: 8428 Explosive volcanism
DE: 8434 Magma migration and fragmentation
DE: 8485 Remote sensing of volcanoes
DE: 8494 Instruments and techniques
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting