A subduction zone (Bebout et al., 1996) is an area where two plates are converging, with one plate moving beneath the other. As the down-going (subducting) plate moves deeper, it transports water into depth where it is heated and released. The heat from the mantle and core causes the surrounding rocks to melt and become fresh magma for volcanic eruptions. The down-going plate is recycled in the Earth’s mantle. At the Cascadia subduction zone the ocean crust of the Juan de Fuca plate is subducting beneath the continental crust of the North American plate. At subduction zones, there usually is an area where the two plates become locked. This means that they are not slipping past each other and frictional stress can build up, storing large amounts of energy. When this stress finally...