what are oceanic plates?
 Oceanic crust is the uppermost layer of an oceanic tectonic plate. The crust overlies the solidified and uppermost layer of the mantle. The crust and the solid mantle layer together comprise an oceanic plate.The plates of the Earth together are referred to as the lithosphere.Oceanic crust is the result of erupted mantle material originating from below the plate, cooled and in most instances, modified chemically by seawater.This occurs mostly at mid-ocean ridges, but also at scattered hotspots, and also in rare but powerful occurences known as flood basalt eruptions. 