We study the dynamics of spreading of miscible ethanol-water films on the surface of a deep water layer, when an ethanol-water droplet is gently deposited on the water layer. Measurements from particle-based visualizations for drops of radii ranging from 0.9 mm to 1.1 mm and ethanol concentrations (Ce) ranging from 20% to 100% show that the radius rf and the velocity Uf of the expanding front of the film show a novel scaling with time of rf ~t^1/4 and Uf ~t^-3/4 respectively; they also show a dependence on Ce and rd. A model, in which the surface tension difference across the film balances the viscous resistance within the film, is shown to explain these dependencies. Novel plume-like instabilities are seen at the periphery of the expanding circular ethanol-water films; we measure their lengths (Lp), radial velocities (Up), and mean azimuthal spacings (