The dynamics of dike propagation

Overview The aim of this chapter is to provide an overview of physical models of the dynamics of propagation of magmatic dikes. Experimental studies of fissure propagation provide an important way of validating hypotheses made in theoretical models, and hence provide a vital link between theory and field observations. Geological field observations of dikes can provide detailed information about rock and magma properties and post-emplacement dike geometry, but do not permit assessment of propagation rates. Conversely, geophysical studies can record dike emplacement as it takes place, allowing estimates of speed or demonstrating intermittency of propagation, but giving little information about dike geometry. We highlight some examples of field observations of dike dynamics that provide useful constraints for models. We discuss the main assumptions and key results of theoretical models that treat dike emplacement into both homogeneous and heterogeneous media. These models predict both the geometry of a propagating dike and the emplacement dynamics (e.g., speed), although they require assumptions about the source conditions, such as magma supply rates. There are open questions arising from shortcomings of current theory, which can be addressed using laboratory experiments that permit detailed investigation of real-time geometric and dynamic information. Notable among recent studies are attempts to quantify factors that may lead to arrest of a dike before it reaches the surface, the potential for solidification to influence the dynamic regime of propagation, and the influence of three-dimensional fracturing effects on propagation.