The Campbell Plateau is a large oceanic plateau south of New Zealand and the Chatham Rise . It originated in the Gondwanan breakup and is part of Zealandia , a largely submerged continent . The above sea level parts of the plateau — the Bounty Islands , Antipodes Islands , Auckland Islands and Campbell Island — form part of the New Zealand Subantarctic Islands which were declared a World Heritage Site in 1998. Large parts of the Campbell Plateau lie less than 1000 m below sea level. It rises to 500 m at the Pukaki Rise and emerges above sea level at the Auckland and Campbell Islands.
24-571: The Emerald Fracture Zone ( 62°S 170°E / 62°S 170°E / -62; 170 ) is an undersea fracture zone running the distance from the southwest corner of the Campbell Plateau to the northern tip of Iselin Bank . The name was proposed by Dr. Steven C. Cande of the Scripps Institution of Oceanography for the vessel Emerald , which traversed this region in 1821, and
48-622: A half-graben geometry. Other common geometries include metamorphic core complexes and tilted blocks . Examples of active continental rifts are the Baikal Rift Zone and the East African Rift . Divergent plate boundaries are zones of active extension as the crust newly formed at the mid-ocean ridge system becomes involved in the opening process. Zones of thickened crust, such as those formed during continent-continent collision tend to spread laterally; this spreading occurs even when
72-596: A specific oceanic location or ocean current is a stub . You can help Misplaced Pages by expanding it . Campbell Plateau Covering an area of 800,000 km (310,000 sq mi), the Campbell Plateau has a gently undulating bathymetry with major rises trending east–west: Campbell Island Rise, Pukaki Rise, and Bounty Island Ridge. There are two near-parallel rises on the western margin: Stewart Island–Snare Island Rise and Auckland Island platform. The continental slopes are steep on western and southern margins while
96-745: A wind-driven Ekman transport of surface water across the Campbell Plateau. At the Subtropical Convergence the Southland Current rounds the South Island and flows north-east along the island's east coast. From there it entrains Subantarctic and subtropical waters across the north-western Campbell Plateau before branching over the Chatman Rise north of the plateau. 51°S 171°E / 51°S 171°E / -51; 171 Extensional tectonics Extensional tectonics
120-403: Is concerned with the structures formed by, and the tectonic processes associated with, the stretching of a planetary body 's crust or lithosphere . The types of structure and the geometries formed depend on the amount of stretching involved. Stretching is generally measured using the parameter β , known as the beta factor , where t 0 is the initial crustal thickness and t 1
144-471: Is offset along strike such as to create a gap e.g. a left-stepping bend on a sinistral fault, a zone of extension or transtension is generated. Such bends are known as releasing bends or extensional stepovers and often form pull-apart basins or rhombochasms . Examples of active pull-apart basins include the Dead Sea , formed at a left-stepping offset of the sinistral sense Dead Sea Transform system, and
168-523: Is the final crustal thickness. It is also the equivalent of the strain parameter stretch . In areas of relatively low crustal stretching, the dominant structures are high to moderate angle normal faults, with associated half grabens and tilted fault blocks . In areas of high crustal stretching, individual extensional faults may become rotated to too low a dip to remain active and a new set of faults may be generated. Large displacements may juxtapose syntectonic sediments against metamorphic rocks of
192-520: Is unusually thin. The reason for this is debated, but there are two likely candidates: either an Early Cretaceous extensional event or the Late Cretaceous break-up between New Zealand and Antarctica. Cretaceous extension between the South Island and the Campbell Plateau created the Great South Basin in which 8 km of sediments have since accumulated. The Bounty Trough was created during
216-769: The Macquarie Triple Junction at its south western margin and mainly acts as a leaky transform fault zone between the Antarctic Plate and Pacific Plate. It has only moderate current seismic activity. An example was the M ww 5.9 event of 9 June 2023. The clockwise rotation of the Pacific Plate and Antarctic Plate between 12 and 10 million years ago resulted in fragmentation of the long-offset Emerald transform fault and its replacement over less than 2 million years with closely spaced, highly variable transform offsets that were joined by short ridge segments. There
240-580: The Niger Delta , large counter-regional faults are observed, dipping back towards the continent, forming large grabenal mini-basins with antithetic regional faults. Areas of extensional tectonics are typically associated with: Rifts are linear zones of localized crustal extension. They range in width from somewhat less than 100 km up to several hundred km, consisting of one or more normal faults and related fault blocks. In individual rift segments, one polarity (i.e. dip direction) normally dominates, giving
264-487: The Sea of Marmara , formed at a right-stepping offset on the dextral sense North Anatolian Fault system. Back-arc basins form behind many subduction zones due to the effects of oceanic trench roll-back which leads to a zone of extension parallel to the island arc . A passive margin built out over a weaker layer, such as an overpressured mudstone or salt , tends to spread laterally under its own weight. The inboard part of
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#1732851585866288-685: The Subantarctic Front (SAF). It reaches New Zealand with an average volume of c. 130×10 m /s. South of New Zealand it is partly deflected in the Tasman Sea as a broad, weak flow. The main part of the ACC, however, passes around the Macquarie Ridge together with the SAF and then flows north along the eastern margin of the Campbell Plateau. At 55°S and 50°S the ACC turns eastward again. There is, however,
312-407: The royal albatross , crested penguin , and Hooker's sea lion . The southern part of South Island ( Fiordland , Southland and Otago ) can be considered part of the Campbell Plateau, both biologically and geologically. Endemic taxa include the spider genus Gohia , the frog species Puhuruhuru patersoni , and nine genera of beetles. The order Lepidoptera (moths and butterflies) also link
336-751: The Early Cretaceous or Jurassic. The southern margin of the plateau was located next to the continental shelves of the eastern Ross Sea and Marie Byrd Land. There are two systems of magnetic anomalies on the Campbell Plateau: the Stokes Magnetic Anomaly System (SMAS) and the Campbell Magnetic Anomaly System (CMAS). The origin and relationship of these anomalies remain unclear. The islands are important breeding centres for both endemic and circumpolar species, including
360-514: The collisional event is still in progress. After the collision has finished the zone of thickened crust generally undergoes gravitational collapse , often with the formation of very large extensional faults. Large-scale Devonian extension, for example, followed immediately after the end of the Caledonian orogeny particularly in East Greenland and western Norway . When a strike-slip fault
384-467: The island share several endemic taxa, including six beetle species, a fly genus ( Schoenophilus ) and a vascular plant genus ( Pleurophyllum ). Further support for this connection comes from the aralia genus Stilbocarpa and possibly the cormorant . South of the Campbell Plateau, the eastward-flowing Antarctic Circumpolar Current (ACC) is bounded by the Antarctic Polar Front (APF) and
408-584: The island. The Antipodes Islands, in contrast, are composed of Quaternary alkaline olivine basalts. Most plate-tectonic reconstructions place the Campbell Plateau together with the Lord Howe Rise, the Challenger Plateau, and the Ross Sea before the break-up of Gondwana. These four structures have similar crustal thickness and underwent the same pre-break-up process of crustal thinning and underplating during
432-485: The mid to lower crust and such structures are called detachment faults . In some cases the detachments are folded such that the metamorphic rocks are exposed within antiformal closures and these are known as metamorphic core complexes . Passive margins above a weak layer develop a specific set of extensional structures. Large listric regional faults dipping towards the ocean develop with rollover anticlines and related crestal collapse grabens . On some margins, such as
456-533: The northern margin slowly falls into the Bounty Trough. The Campbell Plateau is a roughly triangular, cratonic microcontinent which formed during the break-up of Gondwana around 80 Ma. Large parts of the plateau are made of Palaeozoic or older granites overlain by much younger shield volcanoes who form the Auckland and Campbell Islands. The Campbell Plateau is made of continental crust, but, as such,
480-590: The ocean floor geology of the region based on magnetic data assigns the area of the fault zone to oceanic crust of Eocene to Miocene age and so would distinguish other north south fault zones in the Cretaceous oceanic crust to the south east of the Campbell Plateau. The fracture zone is related to the Hjort Trench that represents the southern end of the Australian Plate and Pacific Plate convergence, contains
504-576: The same process. The Campbell Plateau can have been affected by this extension or an earlier event. The islands are composed of continental rocks. The western islands, Auckland, Snares, and Stewart, have a 100–120 Ma-old Middle Cretaceous basement made of granites. On Snares and Stewart islands schists of similar age suggest metamorphism ceased about this time. The basement of Campbell Island and Fiordland are both made of Palaeozoic schists. Bounty Islands are made of 189 Ma-old granodiorite and Precambrian-Cambrian greywackes have been dredge near
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#1732851585866528-528: The southern South Island to the New Zealand Subantarctic Islands. Macquarie Island is biologically but not geologically related to the Campbell Plateau. The island is made of oceanic crust that formed at the Macquarie triple junction . This triple junction was originally located adjacent to the Campbell Plateau but is now isolated south of it due to sea floor spreading. The plateau and
552-507: Was asymmetrical spreading rates in the area of the leaky transform fault zone near the Macquarie Triple Junction. [REDACTED] This article incorporates public domain material from "Emerald Fracture Zone" . Geographic Names Information System . United States Geological Survey . This article about a regional geological feature is a stub . You can help Misplaced Pages by expanding it . This article about
576-562: Was approved by the Advisory Committee for Undersea Features in June 1997. The Emerald Basin to its north west was named from the same source. Some have restricted the name to the southern east west orientated transform fault zone but the north south orientated faults that define the eastern boundary of the Emerald Basin are generally included in the literature. The latest reinterpretation of
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