STABILITY OF RIDGE-RIDGE-RIDGE TRIPLE JUNCTIONS BASED ON THE MECHANICS OF RIFT INTERACTION: THE NORTHERN GALÁPAGOS AND RODRIGUEZ TRIPLE JUNCTIONS

Abstract

Although known to be kinematically stable, Ridge-Ridge-Ridge (RRR) triple junctions sometimes display a complex sequence of short-lived rifts and no direct connection between the ridges. The Galápagos Triple Junction, in the Eastern Equatorial Pacific Ocean and the Rodriguez Triple Junction, in the Central Indian Ocean, serve as end-members of stability observed as RRR triple junctions. I propose that the stability of RRR triple junctions, principally whether secondary rifts are generated or direct connection between the spreading centers is favored, can be understood based on the mechanics of crack interaction. I develop numerical models of the stress field in an elastic plate under tension, with cracks representing rifts in the vicinity of a RRR triple junction and GIS spatial analysis to demonstrate the factors that control RRR triple junction's stability. Although RRR triple junctions are kinematically stable, rift junctions are mechanically unstable, generating a rapidly evolving and complex plate boundary.