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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 and stretching to the Macquarie Triple Junction south of New Zealand.

The divergence rate between the two plates along the ridge is believed to vary from about 5.4 centimetres per year (2.1 in/year) near 65°S to 7.4 centimetres per year (2.9 in/year) near the Udintsev Fracture Zone at 55°S.

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.

The Louisville Ridge

Stretching for 4,300 km north-west from the Eltanin Fault System which intersects the Pacific-Antarctic Ridge to the Osbourn Seamount at Tonga and Kermadec Junction 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

References

1. General citations for named fracture zones are at page Misplaced Pages:Map data/Fracture zone and specific citations are in interactive detail.
2. "Marine Gazetteer:Pacific-Antarctic Ridge". Retrieved 6 November 2023.
3. "Pacific-Antarctic Ridge". www.britannica.com. Retrieved 5 April 2013.
4. Geli, L; Bougault, H; Aslanian, D; Briais, A; Dosso, L; Etoubleau, J; Le Formal, JP; Maia, M; Ondreas, H; Olivet, JL; Richardson, C (1997). "Evolution of the Pacific-Antarctic Ridge South of the Udintsev Fracture Zone". Science. 278 (5341): 1281–1284. doi:10.1126/science.278.5341.1281.
5. ^ Wobbe, F; Gohl, K; Chambord, A; Sutherland, R (2012). "Structure and breakup history of the rifted margin of West Antarctica in relation to Cretaceous separation from Zealandia and Bellingshausen plate motion". Geochemistry, Geophysics, Geosystems. 13 (4). doi:10.1029/2011GC003742.
6. Keating, Barbara H. (1987). Seamounts, Islands, and Atolls. American Geophysical Union. ISBN 0-87590-068-2.
7. "Isotopic evidence for a hotspot origin of the Louisville Seamount Chain". www.agu.org. Retrieved 5 April 2013.

Further reading

• Cande, S. C.; Raymond, C. A.; Stock, J.; Haxby, W. F. (1995). "Geophysics of the Pitman Fracture Zone and Pacific-Antarctic plate motions during the Cenozoic". Science. 270 (5238): 947–953. Bibcode:1995Sci...270..947C. doi:10.1126/science.270.5238.947. S2CID 128877575.

v t e Mid-ocean ridges
Present	Central Indian Chile East Pacific Explorer Gakkel Gorda Juan de Fuca Mid-Atlantic Pacific-Antarctic South American-Antarctic Southeast Indian Southwest Indian
Former	Aegir Alpha Antarctic-Phoenix Kula-Farallon Mid-Labrador Osbourn Trough Pacific-Farallon Pacific-Kula
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v t e Tectonic plates
Major plates	African Antarctic Eurasian Indo-Australian Australian Indian North American Pacific South American
Minor plates	Amurian Arabian Burma Caribbean Caroline Cocos Indian Nazca New Hebrides Okhotsk Philippine Scotia Somali Sunda Yangtze
Microplates	Adriatic Aegean Sea Anatolian Balmoral Reef Banda Sea Bird's Head Capricorn Coiba Conway Reef Explorer Futuna Galápagos Gonâve Gorda Greenland Halmahera Iberian Iranian Juan de Fuca Juan Fernández Kerguelen Kermadec Lwandle Madagascar Malpelo Manus Maoke Mariana Molucca Sea Niuafo’ou North Andes North Bismarck North Galápagos Okinawa Panama Pelso Philippine Mobile Belt Rivera Rovuma Sangihe Seychelles Shetland Solomon Sea South Bismarck South Sandwich Timor Tisza Tonga Trobriand Victoria Woodlark
Ancient plates	Baltic Bellingshausen Charcot Cimmeria Farallon Insular Intermontane Izanagi Kula Lhasa Malvinas Moa Phoenix Kshiroda
Oceanic ridges	Aden Ridge Carlsberg Ridge Central Indian Ridge Chile Ridge Cocos Ridge East Pacific Rise Explorer Ridge Gakkel Ridge Galápagos Spreading Center Gorda Ridge Juan de Fuca Ridge Mid-Atlantic Ridge Knipovich Ridge Kolbeinsey Ridge Mohns Ridge Reykjanes Ridge Pacific–Antarctic Ridge South American–Antarctic Ridge Southeast Indian Ridge Southwest Indian Ridge
Ancient oceanic ridges	Aegir Ridge Alpha Ridge Antarctic–Phoenix Ridge Kula–Farallon Ridge Mid-Labrador Ridge Pacific–Farallon Ridge Pacific–Kula Ridge
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61°59′58″S 157°00′01″W / 61.999555°S 157.000165°W / -61.999555; -157.000165

• Underwater ridges of the Pacific Ocean
• Underwater ridges of the Southern Ocean
• Geology of the Southern Ocean