Constructive plate boundaries are plates that are moving apart, plates move extremely slowly.(bbc bitesize)
Conservative Plate Boundaries
Conservative plate boundaries do not have volcanoes along them (bbc bitesize). but earthquakes can occur the San Andreas fault which runs down the western side of America is a conservative plate boundary. This fault caused the great San Francisco earthquake and fire of 1906. (bbc)
Destructive Plate Boundary
At this kind of boundary the plates are moving towards each other. It usually involves both a oceanic and a continental plate. The oceanic plate (the beige one on my diagram) is more dense than the continental plate so it goes under it. It then is melted and forms magma and if the plates are not completely smooth they will stick this is how earthquakes happen. The magma collects and can form something called a magma chamber. This magma rises through lots of cracks and imperfections in the continental crust to form volcanoes.(bbc bitesize)