Tectonic plate boundary in the South Pacific Ocean
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.[1]
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.[4]: 1281
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.[5]: 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.[5]: 14
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[6]
is a long line of seamounts called the
Louisville Ridge – the longest such chain in the Pacific[7] – thought to have formed from the Pacific Plate sliding over a long-lived center of upwelling
magma called the
Louisville hotspot.