Rw. Griffiths et Jh. Fink, SOLIDIFYING BINGHAM EXTRUSIONS - A MODEL FOR THE GROWTH OF SILICIC LAVA DOMES, Journal of Fluid Mechanics, 347, 1997, pp. 13-36
In a previous study of the effects of cooling and solidification on fl
ows issuing onto a horizontal plane and spreading under gravity we con
sidered the case of a viscous fluid that solidifies to form a thin sur
face crust with a finite yield strength. In that case, the coupling of
solidification and viscous stresses in the flow led to a sequence of
flow regimes or styles of flow and crustal deformation. Here, we study
the spreading, from a small source, of a plastic material having a yi
eld strength before cooling. In this case the fluid again begins to fr
eeze as it spreads radially under gravity, and forms a dome having a s
urface crust which is stronger than the extruded fluid. If cooling is
sufficiently rapid compared tc, gravity-driven spreading, the flow is
found to be controlled by solidification. The flow again takes on one
of a number of flow regimes depending on the pace of solidification re
lative to the rate of lateral flow, or extrusion rate. However, these
flow regimes are quite different from those for the viscous extrusions
, implying that the :internal yield stress has a strong influence on t
he behaviour. Styles of flow ranged from inflation of an axisymmetric
dome to irregular extrusion of lateral lobes and vertical spines. Thes
e qualitatively different regimes have much in common with the eruptio
n styles of volcanic lava domes produced by effusion of extremely visc
ous silicic magmas which may possess a yield strength, and the model p
rovides information about the factors influencing the morphology and h
azards of such volcanic flows.