  We report an experimental study of the intermittent dynamics of a gas flowing
through a column of a non-Newtonian fluid. In a given range of the imposed
constant flow rate, the system spontaneously alternates between two regimes:
bubbles emitted at the bottom either rise independently one from the other or
merge to create a winding flue which then connects the bottom air entrance to
the free surface. The observations are reminiscent of the spontaneous changes
in the degassing regime observed on volcanoes and suggest that, in the nature,
such a phenomenon is likely to be governed by the non-Newtonian properties of
the magma. We focus on the statistical distribution of the lifespans of the
bubbling and flue regimes in the intermittent steady state. The bubbling regime
exhibits a characteristic time whereas, interestingly, the flue lifespan
displays a decaying power-law distribution. The associated exponent, which is
significantly smaller than the value 1.5 often reported experimentally and
predicted in some standard intermittency scenarios, depends on the fluid
properties and can be interpreted as the ratio of two characteristic times of
the system.
