Diego Cordoba, Charles Fefferman Growth of solutions for QG and 2D Euler equations (135K, Postscript) ABSTRACT. We study the rate of growth of sharp fronts in the quasi-geostrophic and 2D incompressible Euler equations. The development of sharp fronts are due to a mechanism that piles up level sets very fast. Under a semi-uniform collapse, we obtain a lower bound of the minimum distance between the level sets.