Large volcanic eruptions introduce huge quantities of aerosols into the stratosphere. Volcanic aerosols heat the stratosphere, thereby altering the global circulation of air. This research uses simulations of the 1991 Mt. Pinatubo eruption to study the resulting circulation changes, and the dynamical processes which govern them. We find that stratospheric composition is altered by increased tropical vertical motion, and that the seasonal cycle of the global circulation is significantly dampened.