The Earth is made up of a dozen or so major plates and several minor plates.
Tectonic plates are constantly on the move.
You'll notice that most plates are part continental and part oceanic. Take the North American plate, for example. Its western half is dominated by the North American continent, but its eastern half forms part of the Atlantic Ocean basin. In comparison, the Pacific plate is essentially all oceanic. This site is a cooperative endeavor of the US Geological Survey Western Earth Surface Processes Team and the National Park Service .