  The understanding of dynamic failure in amorphous materials via the
propagation of free boundaries like cracks and voids must go beyond elasticity
theory, since plasticity intervenes in a crucial and poorly understood manner
near the moving free boundary. In this Letter we focus on failure via a
cavitation instability in a radially-symmetric stressed material, set up the
free boundary dynamics taking both elasticity and visco-plasticity into
account, using the recently proposed athermal Shear Transformation Zone theory.
We demonstrate the existence (in amorphous systems) of fast cavitation modes
accompanied by extensive plastic deformations and discuss the revealed physics.
