Usually, a sliding plate boundary(conservative boundary) causes earthquakes, while spreading plate boundaries(constructive) usually cause shield volcanoes.
Answer:
Oceanic crust is created as magma rises to fill the gap between diverging tectonic plates and is consumed in subduction zones. It is geologically young, with a mean age of 60 Ma, and is thin, averaging 6.5 km in thickness. Oceanic crust consists almost exclusively of extrusive basalt and its intrusive equivalents.
