Thompson, N. D., 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.
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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:||Geography and Environmental Studies|
Science > Earth Sciences
|Group:||School of Applied Sciences > Centre for Conservation, Ecology and Environmental Change|
|Deposited By:||Professor Matthew Bennett|
|Deposited On:||05 Apr 2010 18:52|
|Last Modified:||07 Mar 2013 15:23|
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