Title:
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Lava emplacement dynamics
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Recent advances in the study of lava emplacement dynamics have focused on the numerical
solutions of increasingly complex fluids, frequently with an onus on visco-plasticity. The effects of
temperature-dependent viscosity in the extrusion of lava have been under-investigated, particularly
with reference to experimental analogues.
Golden syrup displays a strongly temperature-dependent viscosity, and in a series of experiments
was extruded from a point source onto a slope in a cooled environment. The long flows
underestimated the isothermal numerical predictions of Lister (1992) in spatial extent, and can be
modelled to expand according to basic isothermal theory, but with a time-dependent bulk viscosity
that varies with time to the power of fJ, which takes the values 0.25 to 0.79 and increases with
increasing viscosity ratio and decreasing Peclet number. Cooled flows developed considerably
greater height proftles than in isothermal experiments, leading to steep flow fronts and bulked-up
flow plateaus.
The flows developed clear central channels of hot syrup, bordered by margins of cooled, rippled
and/or tom skin, with small-scale fold wavelengths (Lr) of 1 mrn, Channel widths are found to be
linear functions of flow rate, and at given flow rates and ambient temperatures, relative widths are a
function of the cotangent of the angle of slope. Larger second-generation folds (La.) developed
downstream, and the ratio A (La.ILt) is of the range 10.5 to 29.5. Flow margins were perturbed and
developed overflow crease structures.
Fieldwork in Cameroon investigated the character and morphologies of the 1999 lava flows, and
their relation to local and source dynamics. Structures are analysed qualitatively and quantitatively;
more detailed arguments are developed on the processes of levee formation, and systematic links
between flow dynamics and levee-channel interface geometry are presented in light of Cameroonian
examples. Modem field analyses are supported by a historical, archive-sourced investigation of past
activity that collates and interprets prior observations for the modem volcanologist
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