Blast Waves The main workhorse of the explosion is the blast wave. The heat coupled with the rapidly expanding gases causes an area of high pressure that expands out from the initiation point. This high pressure area is a shock wave and it expands outward causing mayhem and destruction to anything in its path. As the rapid displacement of air and material from the expanding shock wave occurs a vacuum is created at the origination point and air and surrounding gases rush back in to restore equilibrium. This generates a secondary reverse shock wave that travels back to the origin of the explosion.