A model has been made of the opening of the Atlantic Ocean shows how the simplest geometric separation of the continents around the Atlantic might account for the gross structure and some hitherto anomalous features of its floor, and might explain the position and sense of wrench faulting in the Alpine orogenic belts around the Mediterranean and Caribbean. A time scale suggested for the opening is consistent with the available paleontological and magnetic survey data. Some predictions regarding the results of the United States Deep Sea Drilling Project have been made.