Hikurangi Plateau
The Hikurangi Plateau is an oceanic plateau in the South Pacific Ocean east of the North Island of New Zealand. It is part of a large igneous province (LIP) together with Manihiki and Ontong Java, now located 3,000 km (1,900 mi) and 3,500 km (2,200 mi) north of Hikurangi respectively.Mount Hikurangi, in Māori mythology the first part of North Island to emerge from the ocean, gave its name to the plateau.
The Hikurangi Plateau covers approximately 400,000 km2 (150,000 sq mi) and reaches 2,500–3,000 m (8,200–9,800 ft) below sea level.
Hikurangi Plateau is cut by the Hikurangi Channel, a 2000 km abyssal channel that starts at Kaikoura and runs along the Hikurangi Trench as far as the Mahia Peninsula before crossing the plateau and ending in the South-west Pacific abyssal plain.
Two models have been proposed for the formation of Hikurangi. It can be derived from the mantle plume that caused the break-up of Gondwana and the separation of Zealandia from Antarctica 107 Ma. Alternatively, it could have formed together with other Pacific plateaux around 120 Ma as part of the Ontong Java-Manihiki-Hikurangi mega-plateau, in which case Hikurangi must have drifted thousands of kilometres during the Cretaceous silent period (84–121 Ma) before colliding with Gondwana.
A 2010 study of isotopic data supported the mega-plateau or "Greater Ontong Java Event" model. The study added several basins as remains of this LIP event, including the north-west part of the Central Pacific, Nauru, East Mariana, and Lyra basins — submarine volcanism that must have covered 1% of Earth's surface and had a dramatic impact on life on Earth. There are, nevertheless, traces in seamounts on Hikurangi of a second Late Cretaceous magmatic event contemporaneous with volcanism on New Zealand and associated with the final break-up of Gondwana.
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