One example of a ridge is the Mid-Atlantic Ridge, an undersea chain of mountains that formed as two pairs of tectonic plates spread apart: the North American Plate and the Eurasian Plate in the north, and the South American Plate and the African Plate in the south.
Plate Boundaries: Convergent, Divergent, Transform.
Transform boundaries are where two of these plates are sliding alongside each other. This causes intense earthquakes, the formation of thin linear valleys, and split river beds. The most famous example of a transform boundary is the San Andreas Fault in California.
Plates at our planet's surface move because of the intense heat in the Earth's core that causes molten rock in the mantle layer to move. It moves in a pattern called a convection cell that forms when warm material rises, cools, and eventually sink down. As the cooled material sinks down, it is warmed and rises again.