Northampton Electronic Collection of Theses and Research

Development of characteristic volcanic debris avalanche deposit structures: New insight from distinct element simulations

Thompson, N., Bennett, M. R. and Petford, N. (2010) Development of characteristic volcanic debris avalanche deposit structures: New insight from distinct element simulations. Journal of Volcanology and Geothermal Research. 192(3-4), pp. 191-200. 0377-0273.

Item Type: Article
Abstract: Large-scale catastrophic collapse of volcanic edifices is a relatively common phenomenon in the geologic record. However, the processes that occur during debris avalanche emplacement remain poorly understood and must generally be inferred from analysis of avalanche deposits in the field, which are recognized to contain a suite of recurrent features, such as conical surface hummocks and toreva block ridges. This study uses the distinct element numerical modelling method to investigate debris avalanche emplacement processes, because it allows brittle deformation of the failure mass to be examined. After describing the material calibration and model setup necessary for modelling the geomechanical behaviour of a failed edifice flank, a sequence of emplacement snapshots is described. The simulated debris avalanche is seen to evolve from initial block sliding, through extension with horst and graben structures defined by propagation and offset of large-scale discontinuities, to a final stage in which the avalanche flows down-valley. The numerical model is consistent with emplacement theory in the literature and allows for a more precise view of the processes at work during failure and the deposits created thereby. For example, toreva blocks are formed in the medial and proximal sections of the failure through top-down propagation of normally offset discontinuities developed from upper surface tension. A mechanism for surface hummock formation is also recognized involving the retention of surface blocks. As these and other characteristic deposit features are formed from a flank with homogeneous material properties, brittle deformation of the initially listric- shaped failure mass and associated macroscopic structural evolution are recognized as important factors in failure evolution and subsequent deposit morphology.
Uncontrolled Keywords: edifice flank instability, volcanic debris avalanches, deposit morphology, distinct element modelling
Subjects: Q Science > QE Geology > QE500 Dynamic and structural geology > QE521 Volcanoes and earthquakes
Creators: Thompson, Nick, Bennett, Matthew R and Petford, Nick
Publisher: Elsevier
Faculties, Divisions and Institutes: University Faculties, Divisions and Research Centres - OLD > University Departments > Directorate
Faculties > Faculty of Arts, Science & Technology > Environmental Science
Date: 2010
Date Type: Publication
Page Range: pp. 191-200
Journal or Publication Title: Journal of Volcanology and Geothermal Research
Volume: 192
Number: 3-4
Language: English
ISSN: 0377-0273
Status: Published / Disseminated

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