LEADER 00000nam  2200349   4500 
001    AAI3278728 
005    20081111094052.5 
008    081111s2007    ||||||||||||||||| ||eng d 
020    9780549202530 
035    (UMI)AAI3278728 
040    UMI|cUMI 
100 1  Durant, Adam J 
245 10 On water in volcanic clouds 
300    242 p 
500    Source: Dissertation Abstracts International, Volume: 68-
       08, Section: B, page: 5085 
500    Adviser: William Rose 
502    Thesis (Ph.D.)--Michigan Technological University, 2007 
520    Volcanic clouds and tephra fallout present a hazard to 
       aviation, human and animal health (direct inhalation or 
       ingestion, contamination of water supplies), and 
       infrastructure (building collapse, burial of roads and 
       railways, agriculture, abrasive and chemical effects on 
       machinery). Understanding sedimentation processes is a 
       fundamental component in the prediction of volcanic cloud 
       lifetime and fallout at the ground, essential in the 
       mitigation of these hazards. The majority of classical 
       volcanic ash transport and dispersion models (VATDM) are 
       based solely on fluid dynamics. The non-agreement between 
       VATDM and observed regional-scale tephra deposit 
       characteristics is especially obvious at large distances 
       from the source volcano. In meteorology, the processes of 
       hydrometeor nucleation, growth and collection have been 
       long-established as playing a central role in 
       sedimentation and precipitation. Taking this as motivation,
       the hypothesis that hydrometeor formation drives 
       sedimentation from volcanic clouds was tested 
520    The research objectives of this dissertation are: (1) To 
       determine the effectiveness of tephra particles in the 
       catalysis of the liquid water to ice phase transformation,
       with application to ice hydrometeor formation in volcanic 
       clouds. (2) To determine the sedimentological 
       characteristics of distal (100s km) tephra fallout from 
       recent volcanic clouds. (3) To assess particle fallout 
       rates from recent volcanic clouds in the context of 
       observed deposit characteristics. (4) To assess the 
       implications of hydrometeor formation on the enhancement 
       of volcanic sedimentation and the potential for cloud 
       destabilization from volcanic hydrometeor sublimation 
520    Dissertation Overview. The following chapters present the 
       analysis, results and conclusions of heterogeneous ice 
       nucleation experiments and sedimentological 
       characterization of several recent tephra deposits. The 
       dissertation is organized in three chapters, each prepared
       in journal article format. In Chapter 1, single ash 
       particle freezing experiments were carried out to 
       investigate the effect of ash particle composition and 
       surface area on water drop freezing temperature. In 
       Chapter 2, the tephra deposit from the 18 May 1980 
       eruption of Mount St. Helens, USA, was reanalyzed using 
       laser diffraction particle size analysis and hydrometeor-
       induced sedimentation mechanisms are considered. In 
       Chapter 3, fallout from the 18 August 1992 and 16--17 
       September 1992 eruptions of Mount Spurr, USA, was analyzed
       and particle sedimentation and cloud microphysics were 
       modeled to assess the potential for cloud destabilization 
       from hydrometeor sublimation 
590    School code: 0129 
590    DDC 
650  4 Geology 
650  4 Atmospheric Sciences 
690    0372 
690    0725 
710 2  Michigan Technological University 
773 0  |tDissertation Abstracts International|g68-08B 
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