Experiments on internal strain in lava dome cross sections

Abstract

Simple experiments have been conducted to study the strain evolution in lava dome cross sections. A viscous fluid is injected vertically from a reservoir into a feeding conduit. Silicone putty is used as analogue magma. Two-dimensional experiments allow the assessment of the internal strain within the dome. Particle paths are symmetrical on either side of a central line passing through the feeding conduit and display parabolic trajectories. The highest strain zone is located above the extrusion zone. In cross sections, stretch trajectories show a remarkable concentric pattern, wrapping around the extrusion zone of the analogue magma. To the lateral margins, a triple junction of stretch trajectories defines an isotropic point in the strain field. In the main central part of the dome, an intermediate zone of reversed sense of shearing is caused by a change in the sign of the velocity gradient with respect to that in the upper and lower zones. Knowledge of this evolving strain pattern can provide a better understanding of the evolution of natural domes. Also, it can help to unravel the kinematic history of ancient domes partly removed by erosion.

Comparative analyses of glass fragments from brittle fracture experiments and volcanic ash particles

“…These pre-stresses are consistent with the specific loading situations of magmatic melts in a conduit (Buisson and Merle 2002). This implies that in future studies one can refer-at least qualitatively-to the HIE results of pre-stressed T10 Fig.…”

Towards realistic simulations of lava dome growth using the level set method

“…This central region as well as bulging of the dome, is clearly visible in Fig. 14. Our results appear to behave in a similar fashion to experimental models analyzed by Buisson and Merle [2], however unfortunately they do not include an image of their experimental model at different points in time.…”

“…This is where computational models have the advantage. Here we compare our computational model of generic endogenous dome growth to experimental simulations of analogue lava domes performed by Buisson and Merle [2]. Their 2002 paper considers simple dome analogue models to investigate the internal stress and strain field evolution in an endogenous lava dome by modelling the lava as a very viscous fluid.…”

“…They inject the gel vertically from a reservoir into a feeding conduit and onto a rigid horizontal plane for three-dimensional models and our computational models replicate this experimental set-up. Whilst for two-dimensional models Buisson and Merle [2] inject the silicon gel between two lubricated glass walls. The extrusion rate was kept constant for all their models and they also recorded information about the height, radius and free-surface.…”

“…Buisson and Merles [2] two-dimensional glass confined models make it possible to observe the internal strain field by tracing particle paths or observing the deformation of a carbon grid imprinted onto the fluid. In vertical cross-section particle trajectories are observed to be parabolic and symmetric about the feeding conduit and they observe two types of particle path.…”