Tectonic plate boundary in the South Pacific Ocean
The Pacific-Antarctic Ridge is the southern extension of the East Pacific RiseBathymetric 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[1]
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.[2]
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 the Udintsev fracture zone at 55°S.[5]: 1281 This area of transition in sea floor spreading rate has been mapped by multiple techniques and occurs near the Heirtzler fracture zone.[1]
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.[6]: 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.[6]: 14
Fracture zones
Fracture zones are generally areas of low gravity on the seafloor parallel to a spreading 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 at Tonga and Kermadec Junction[7] is a long line of seamounts called the Louisville Ridge – the longest such chain in the Pacific[8] – thought to have formed from the Pacific Plate sliding over a long-lived center of upwelling magma called the Louisville 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.
^General citations for named fracture zones are at page Wikipedia:Map data/Fracture zone and specific citations are in interactive detail.
^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.
