Periodicity of orogeny

The periodicity of orogeny is discussed in terms of sea floor spreading, plate tectonics and recent orogenic theory. The confusion in discussions of periodicity is due to the lumping of three distinct features together; continental edge orogenies, continental collision orogenies and features due to mid-oceanic rises. Orogenic periodicity is only well developed for continental edge orogenies. This is related to periodicity in mid-oceanic rise activity over the world. If this is shown to be untrue, there is no periodicity to orogeny over the world; and periodicity is only developed on continental edges controlled by one mid-oceanic rise.