The Mid-Atlantic Ridge is a mid-ocean ridge that was built with a divergent tectonic plate boundary.  This ridge is apart of the longest mid-ocean ridge in the world, the Mid-Ocean Ridge System. It also separates  the Eurasian plate and the African plate from the South American plate. The average spreading rate of this ridge is usually about 2.5 cm per year. The Atlantic is actually spreading, causing the continents to spread towards each other.  So, eventually China and California could be border neighbors. Sea floor spreading is a continuous process, so the spreading of the continents is like Pangaea happening all over again, just except backwards.  Talk about deja vu.