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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