Imagine the devastation and force caused by the atom bomb dropped on Nagasaki at the end of World War II in which over 40,000 people died. Now imagine an explosion 10,000 times as powerful. Explosive volcanic eruptions can be that powerful (Figure 8.9). As hot magma beneath the surface interacts with water, gases accumulate and the magma pressure builds up. This pressure grows and grows until these dissolved gases cause it to burst in an enormous explosion