During magma flow and eruptions, the ground and atmosphere are perturbed by changing pressures and forces over a wide range of time scales. These perturbations provide evidence of cyclical and unsteady flow of magma within volcanic conduits and, therefore, carry information about unstable processes that occur during magma flow. Direct observation of flow in volcanic conduits is a major challenge. An alternative approach is to explore the range of behaviours exhibited by experimental systems more amenable to direct observation. This gives: (1) insight into the important physical processes that create flow instability and, (2) data with which to test computer models.
Experimental approaches have used a wide range of analogue fluids to mimic aspects of flows in conduits. These have identified a number of processes involved in generating cyclical and unstable changes in pressure and force, including resonance, stick-slip, dynamics and visco-elastic transitions; however, all appear to depend on the compressibility, or number of compressibilities, of the materials involved. Here, we review the range and applicability of experimental approaches to magma flow in conduits and discuss the insights this has given into the fluid dynamic source mechanisms that generate ground and atmosphere perturbations.