Tectonic plate boundary in the South Pacific Ocean
The Pacific-Antarctic Ridge is the southern extension of theEast Pacific RiseBathymetric andmagnetostratigraphy 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[1][2]
Approximate surface projection on Pacific Ocean of Pacific-Antarctic Ridge (purple). Features associated with fracture zones (orange) are also shown (lighter orange). Click to expand map to obtain interactive fracture zone details.[3]
The Louisville Ridge stretches diagonally across this bathymetric map of the southwest Pacific Ocean towards the Pacific-Antarctic Ridge at right bottom
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 theUdintsev fracture zone at 55°S.[6]: 1281 This area of transition in sea floor spreading rate has been mapped by multiple techniques and occurs near theHeirtzler fracture zone.[1]
The ridge is related to theLate Cretaceous breakup ofGondwana. To the southeast the historicBellingshausen plate separated the Pacific and Antarctic plates between about 84 to 61 million years ago.[7]: Fig 9. 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.[7]: 14
Fracture zones are generally areas of low gravity on the seafloor parallel to aspreading center.[1] The named fracture zones going southwest along the rise, include:
Stretching for 4,300 km (2,700 mi) north-west from the Eltanin fault system which intersects the Pacific-Antarctic Ridge to the Osbourn Seamount atTonga and Kermadec Junction[9] is a long line of seamounts called theLouisville Ridge – the longest such chain in the Pacific[10] – thought to have formed from the Pacific Plate sliding over a long-lived center of upwellingmagma called theLouisville hotspot.
^abcOndréas, H.; Aslanian, D.; Géli, L.; Olivet, J.L.; Briais, A. (2001). "Variations in axial morphology, segmentation, and seafloor roughness along the Pacific‐Antarctic Ridge between 56 S and 66 S".Journal of Geophysical Research: Solid Earth.106 (B5):8521–8546.Bibcode:2001JGR...106.8521O.doi:10.1029/2000JB900394.
^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.
^abcdCande, S.; Raymond, C.; Stock, J.; Haxby, W. (10 November 1995). "Geophysics of the Pitman Fracture Zone and Pacific-Antarctic Plate Motions During the Cenozoic".Science.270 (5238):947–953.doi:10.1126/science.270.5238.947.
