Triple junction stability is a term used in geology. A triple junction is the point at which three plate boundaries meet. These boundaries can either be ridges (R), trenches (T) or transform faults (F). Triple junctions were once defined simply as the meeting point of three spreading ridges. This is because this sort of triple junction is very common, usually with one of the ridges failing (forming an aulacogen) and the other two continuing to open a new ocean. The meeting of 4 or more plates is also theoretically possible but junctions will only exist instantaneously.