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Title: Lava emplacement dynamics
Author: Stansfield, Stewart Anthony
ISNI:       0000 0001 3477 6817
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2004
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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
Supervisor: Sparks, Stephen Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available