Self-turbulizing cascade of wrinkles in a viscous thread

A thread of viscous mineral oil is deposited at the surface of a clean water bath. Because of the lower surface tension of the oil, the thread first spreads, pulled by Marangoni forces acting on its sides in the plane of the bath. This motion however soon destabilizes and the thread core presents longitudinal sinuous wrinkles which amplify because the surface tension gradient is steepened at the extrema of the thread corrugations. We document and analyze the first steps of this instability, and show that the subsequent steps occur, in a catastrophic manner, on ever smaller timescales. The phenomenon indeed proceeds self-similarly down to ever smaller corrugations scales, in an accelerated cascade finally interrupted by the diffusive smearing of the oil thread core in the bath.