Four major plate interactions can occur. One plate can slide underneath the other plate. The plates can slide past one another. The plates can slam into one another. Plates pull apart from one another along rift zones.
Rift zones are the places on the earth where the newest crust is being formed.
The whole oceanic crust can be replaced in about 100 million years. When one plate slides under another one a subduction zone is created. The thicker continental plates are usually not subducted, in most cases the oceanic plates are driven beneath the continental plates. The subducted plate is forced down into regions of high pressure and temperature allowing the plate to melt. The amount of material destroyed at subduction zones is about equal to the amount of material created at rift zones.