Schematic illustrations of the Wilson cycle, the fundamental geological processes controlling the evolution of the continents a-b) A continent rifts, such that the crust stretches, faults and subsides. c) Seafloor spreading begins, forming a new ocean basin. d) The ocean widens and is flanked by sedimented passive margins. e) Subduction of oceanic lithosphere begins on one of the passive margins, closing the ocean basin (f) and starting contiinental mountain building. g) The ocean basin is destroyed by a continental collision, which completes the mountain buliding process. At some later time continental rifting begins again.