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20-472: The Naturaliste Plateau is one of several large submarine plateaus extending from Western Australia into the Indian Ocean . It is a rectilinear plateau that covers an area of 90,000 square kilometres. Its width is about 400 kilometres (250 mi) east-west and 250 km (160 mi) north-south. The water depths are from 1500 to 5000 metres. The Mentelle Basin and Naturaliste Trough lie between

40-632: A mid-ocean ridge that was active from 80 to 60 million years ago, and now lies 800 kilometres offshore from mainland Australia . The Lord Howe Rise contains a line of seamounts called the Lord Howe Seamount Chain which formed during the Miocene period when this part of Zealandia existed over the Lord Howe hotspot . One rhyolite sample has been dated at 97 million years drilled on the southern Lord Howe Rise. Lord Howe Island

60-427: A consequence, they tend to "dock" to continental margins and be preserved as accreted terranes . Such terranes are often better preserved than the exposed parts of continental flood basalts and are therefore a better record of large-scale volcanic eruptions throughout Earth's history. This "docking" also means that oceanic plateaus are important contributors to the growth of continental crust. Their formations often had

80-624: A dramatic impact on global climate, such as the most recent plateaus formed, the three, large, Cretaceous oceanic plateaus in the Pacific and Indian Ocean: Ontong Java, Kerguelen, and Caribbean. Geologists believe that igneous oceanic plateaus may well represent a stage in the development of continental crust as they are generally less dense than oceanic crust while still being denser than normal continental crust. Density differences in crustal material largely arise from different ratios of various elements, especially silicon . Continental crust has

100-604: Is a large, relatively flat elevation that is higher than the surrounding relief with one or more relatively steep sides. There are 184 oceanic plateaus in the world, covering an area of 18,486,600 km (7,137,700 sq mi) or about 5.11% of the oceans. The South Pacific region around Australia and New Zealand contains the greatest number of oceanic plateaus (see map). Oceanic plateaus produced by large igneous provinces are often associated with hotspots , mantle plumes , and volcanic islands — such as Iceland, Hawaii, Cape Verde, and Kerguelen. The three largest plateaus,

120-432: Is part of Zealandia , a much larger continent that is now mostly submerged, and so is composed of continental crust . Some have included the 3,500 m (11,500 ft) deep New Caledonia Basin as within the rise, given its continental crust origin, and this would give a larger total area of 1,950,000 km (750,000 sq mi). The Lord Howe Rise is associated with seafloor spreading which also resulted in

140-759: Is yet more felsic, and so on through geologic time. Lord Howe Rise The Lord Howe Rise is a deep sea plateau which extends from south west of New Caledonia to the Challenger Plateau , west of New Zealand in the south west of the Pacific Ocean . To its west is the Tasman Basin and to the east is the New Caledonia Basin . Lord Howe Rise has a total area of about 1,500,000 km (580,000 sq mi), and generally lies about 750 to 1,200 metres under water. It

160-656: The Caribbean , Ontong Java , and Mid-Pacific Mountains , are located on thermal swells . Other oceanic plateaus, however, are made of rifted continental crust, for example the Falkland Plateau , Lord Howe Rise , and parts of Kerguelen , Seychelles , and Arctic ridges. Plateaus formed by large igneous provinces were formed by the equivalent of continental flood basalts such as the Deccan Traps in India and

180-700: The Snake River Plain in the United States. In contrast to continental flood basalts, most igneous oceanic plateaus erupt through young and thin (6–7 km (3.7–4.3 mi)) mafic or ultra-mafic crust and are therefore uncontaminated by felsic crust and representative for their mantle sources. These plateaus often rise 2–3 km (1.2–1.9 mi) above the surrounding ocean floor and are more buoyant than oceanic crust. They therefore tend to withstand subduction, more-so when thick and when reaching subduction zones shortly after their formations. As

200-854: The Naturaliste Plateau was flanked by what would become two microcontinents : the Batavia and Gulden Draak Knolls, which are now located on the western margin of the Perth Abyssal Plain 1,600 km (990 mi) from Australia. South of the plateau, during some 45 Ma after India and the two knolls broke off, rifting occurred between the plateau and the Bruce Rise , now located off Antarctica. This rifting continued until sea-floor spreading began 83 Ma. Continental metamorphic and granitic basement rocks have been dredged from both knolls. Protolith granite from Gulden Draak

220-527: The creation of the Tasman Sea. The geology has not yet been characterised as well as other parts of Zealandia but when previous samples are analysed with current geological techniques they fit with the Zealandia hypothesis. The seafloor is known to be dominated by soft sediments and the highest quality recent survey only mapped approximately 25,500 km (9,800 sq mi) of the western flank of

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240-411: The highest amount of silicon (such rock is called felsic ). Oceanic crust has a smaller amount of silicon ( mafic rock). Igneous oceanic plateaus have a ratio intermediate between continental and oceanic crust, although they are more mafic than felsic. However, when a plate carrying oceanic crust subducts under a plate carrying an igneous oceanic plateau, the volcanism which erupts on the plateau as

260-799: The mainland and this plateau. The plateau is bordered by the Perth Abyssal Plain in the north and west and the Australian–Antarctic Basin in the south. It is located within the Australian marine park known as the South-west Corner Marine Park . The Naturaliste Plateau formed during the Early Cretaceous 136 Ma when Australia and India broke up and during the Late Cretaceous 83 Ma when Australia and Antarctica broke up. Lavas and intrusive rocks on

280-427: The oceanic crust heats up on its descent into the mantle erupts material which is more felsic than the material which makes up the plateau. This represents a step toward creating crust which is increasingly continental in character, being less dense and more buoyant. If an igneous oceanic plateau is subducted underneath another one, or under existing continental crust, the eruptions produced thereby produce material that

300-598: The other three flanks are relatively steep. The southern flank formed during the Australia-Antarctica break-up, the other flanks during the rifting between India and Australia. The continent ocean transition (COT) is 30–90 km (19–56 mi) wide on the north side and 250 km (160 mi) on the southern side where the plateau is flanked by the Diamantina Fracture Zone . Before India broke off from Australia-Antarctica at 127 Ma,

320-405: The plateau flanks have ages of between 132-128 Ma. The volcanic sequence that consists of alternating basaltic flows and volcaniclastic beds, cut by multiple dikes, was recovered at IODP Site U1513 on the eastern flank. After the volcanic eruption, the Naturaliste Plateau subsided from shelf to bathyal depths during the Early Cretaceous. The eastern flank of the plateau slopes relatively gently, while

340-424: The rise which is less than 1% of the total area of the rise. In this area about 0.1% of the rises seafloor was classed as hard substrata based on a combined area of 31 km (12 sq mi) for 16 volcanic peaks. Sandstone rocks dredged from the central Lord Howe Rise contained granite pebbles that were in the range 216–183 million years old. It was rifted away from Eastern Australia in association with

360-593: The total area of Lord Howe Rise. Further north is the Elizabeth and Middleton part of the Coral Sea Islands , which together with reefs around Lord Howe Island are the most southern coral reefs on Earth. The seabed on the rise is mostly sandy mud with some volcanic outcrops, gravel and boulders. The doubleheader fish, Coris bulbifrons , is endemic to reefs on the Lord Howe Rise and

380-782: Was emplaced in either the Australian Yilgarn Craton or the Antarctic Mawson Craton 2850 Ma. The Mesoproterozoic crust from this knoll is coeval with crust from the Naturaliste Plateau. Neoproterozoic - Cambrian (540–530 Ma) granite gneisses from the Batavia Knoll were emplaced during or after the formation of the Kuunga Orogen . 34°06′S 111°18′E  /  34.1°S 111.3°E  / -34.1; 111.3 Submarine plateau An oceanic or submarine plateau

400-475: Was the last volcano to erupt on the rise 6.5 million years ago. Lord Howe Island and Ball's Pyramid cap a seamount towards the central east of the rise in an area known as the Lord Howe platform. The Lord Howe Seamount Chain extends northwards along the rise. The seamounts provide habitat to a diverse range of marine species which attracts commercial fishers, but cover a very small area, less than 1% of

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