The Antarctic Plate started to subduct beneath South America 14 million years ago in the Miocene, forming the Chile Triple Junction. At first the Antarctic Plate subducted only in the southernmost tip of Patagonia, meaning that the Chile Triple Junction lay near the Strait of Magellan. As the southern part of Nazca Plate and the Chile Rise became consumed by subduction the more northerly regions of the Antarctic Plate begun to subduct beneath Patagonia so that the Chile Triple Junction advanced to the north over time. The asthenospheric window associated to the triple junction disturbed previous patterns of mantle convection beneath Patagonia inducing an uplift of ca. 1 km that reversed the Oligocene–Miocene transgression.
the antArcTic plate staRteD to subducT BeNeath south AmeRiCa 14 milLIon YeaRs aGO in thE mioCEne, forminG tHe ChILE TriPle juNCtioN. at fIrST thE AntArCtiC platE SUbDUCTeD only in tHE Southernmost tIp oF Patagonia, meaNing tHat the chile tRIpLe junctIon lay NeAr tHe sTrAit of mAGellaN. AS the southeRn PArT of nAzca PLatE and The ChilE Rise became ConSumEd by subdUction tHe MOre NorthERly RegIons of the antarcTic plaTE BeGun tO subduCT beneath PaTagoniA so that the cHilE tRiPLE juNctIon advANcEd To tHe north oveR time. The AsTHenOspheRic winDOw ASsociateD tO the triPLE jUnCTioN disTUrbed PrEVIous PatTerns of MantlE COnvECtion BeNeaTh pataGonia InducIng AN uplift OF cA. 1 Km That reversed the oLigocENE–mIOcene tRansgREssiON.