Skip to Main Content
Skip Nav Destination

The triple junction between the Nazca, Antarctic, and South American crustal plates has been mapped at lat 46.4°S, long 75.7° W. The Chile Ridge, an active spreading center opening at a half-rate of 28 mm/yr, can be traced into the axis of the Chile Trench; at the triple junction itself, the axial rift valley abuts the inner wall of the trench. The spreading process does not appear to be modified by proximity to a subduction zone until the actual point of collision: magnetic anomalies formed by sea-floor spreading can be traced to the inner wall of the trench; the depth of the axis of the Chile Ridge does not change with distance from the trench; the free-air gravity minimum associated with the trench decreases in amplitude owing to the elevated bathymetry at the triple junction, but this gravity anomaly continues across the junction; the thick wedge of trench-floor sediments is displaced only at the triple junction itself; and evidence for uplift of the continent also appears to be restricted to the immediate vicinity of the junction. We estimate that the present trench-ridge-trench triplejunction has existed for about 300,000 yr. Before the collision of this segment of the Chile Ridge axis with the trench, the triple junction was of the trench-transform-trench type.

You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Close Modal

or Create an Account

Close Modal
Close Modal