Subduction II
Metamorphism of subducted slab causes a dramatic increase in its density, enhancing its tendency to sink
Metamorphism releases water from subducted slab; water helps both the slab & the overlying asthenosphere to melt, causing volcanism seen on landward side of DOT
Bending, shortening, shearing, & compression in subducted slab causes seismicity unlike that seen elsewhere in earth - intermediate & deep focus earthquakes are not like shallow earthquakes