thumb|300px|The Pacific-Antarctic Ridge is the southern extension of the [[East Pacific Rise]]thumb|300px|Bathymetric and [[magnetostratigraphy mapping with ages of sea floor spreading in millions of years (Ma) before present between Erebus and Udintsev fracture zones on the Pacific-Antarctic Ridge]]thumb|300px|The Louisville Ridge stretches diagonally across this bathymetric map of the southwest Pacific Ocean towards the Pacific-Antarctic Ridge at right bottom
The Pacific-Antarctic Ridge (PAR, Antarctic Pacific Ridge, South Pacific Rise, South Pacific Ridge) is a divergent tectonic plate boundary located on the seafloor of the South Pacific Ocean, separating the Pacific plate from the Antarctic plate. It is regarded as the southern section of the East Pacific Rise in some usages, generally south of the Challenger fracture zone which is associated with a triple junction between the Juan Fernández microplate, the Pacific plate and the Antarctic plate. It stretches from there in a general southwesterly direction to the Macquarie Triple Junction south of New Zealand.
Tectonics
The divergence rate between the two plates along the ridge is believed to vary from about near 65°S to near the Udintsev fracture zone at 55°S. This area of transition in sea floor spreading rate has been mapped by multiple techniques and occurs near the Heirtzler fracture zone.
The ridge is related to the Late Cretaceous breakup of Gondwana. To the southeast the historic Bellingshausen plate separated the Pacific and Antarctic plates between about 84 to 61 million years ago. Until about 33 million years ago, the Proto-Antipodes fracture zone well to the south separated two independent spreading centers, now merged, being the Antarctic–Pacific Ridge and that of the Antarctic–Campbell Plateau. is a long line of seamounts called the Louisville Ridge – the longest such chain in the Pacific – thought to have formed from the Pacific Plate sliding over a long-lived center of upwelling magma called the Louisville hotspot.
See also
- Hollister Ridge
- Oceanic ridge
- List of tectonic plate interactions