Editing Triple junction (section)

===Ridge–trench–fault junctions===
RTF junctions are less common, an unstable junction of this type (an RTF(a)) is thought to have existed at roughly 12[[Mya (unit)|Ma]] at the mouth of the [[Gulf of California]] where the [[East Pacific Rise]] currently meets the [[San Andreas Fault]] zone.<ref>{{cite web |url=http://www.orfeus-eu.org/Announcements/workshop_utrecht/presentations/zhang.pdf |title=Archived copy |access-date=2009-11-21 |url-status=dead |archive-url=https://web.archive.org/web/20110727153513/http://www.orfeus-eu.org/Announcements/workshop_utrecht/presentations/zhang.pdf |archive-date=2011-07-27 }}</ref> The Guadeloupe and Farallon microplates were previously being subducted under the [[North American plate]] and the northern end of this boundary met the [[San Andreas Fault]]. Material for this subduction was provided by a ridge equivalent to the modern [[East Pacific Rise]] slightly displaced to the west of the trench. As the ridge itself was subducted an RTF triple junction momentarily existed but subduction of the ridge caused the subducted lithosphere to weaken and 'tear' from the point of the triple junction. The loss of [[slab pull]] caused by the detachment of this lithosphere ended the RTF junction giving the present day ridge – fault system. An RTF(a) is stable if ab goes through the point in velocity space C, or if ac and bc are colinear.