Zealandia (continent)
Zealandia (zi ː lændiə ), also under the name Tasmantis or New Zealand continent, is a nearly totally lying submerged continent in the Pacific Ocean.
Geography
Zealandia covers an area of three and a half million square kilometers - larger than Greenland or India - which is about half the size of Australia. Its shape is elongate and narrow. Its northern tip is 19 ° south latitude in the vicinity of New Caledonia to the north, the southern tip is located at 56 ° south latitude even beyond the New Zealand Offshore Islands. This corresponds approximately to the distance between Haiti to Hudson Bay or from Sudan to Sweden. Approximately 93 % of Zealandia are under water. The highest point of Zealandia is New Zealand, followed by New Caledonia. Zealandia basically consists of two nearly parallel undersea barriers that vorliegendes by an originally contiguous, but now in two parts ( New Caledonia Basin and Bounty Trough ), elongated basins are separated. The thresholds rise about 1000 m to 1500 m above the level of the surrounding seabed. Some rocky islands reach the water surface.
The largest components of Zealandia are the Lord Howe threshold, the Challenger Plateau, the Campbell Plateau, Norfolk threshold and the Chatham threshold. Smaller regions are the Louisiade plateau, the Mellish - threshold, the characteristic plateau, the Chesterfield Plateau and the Dampier threshold. The apparently isolated lying Gilbert Seamount (northwest of Fiordland ) is also part of Zealandia. It is unknown whether Bollons Seamount (south of the Chatham Islands) is also in communication with Zealandia.
The land masses at both ends of Zealandia, New Caledonia to the north and the islands of New Zealand in the south are, as well as New Zealand itself at the intersection of three floral kingdoms: the Antarctic, the Oceanic and Australian.
Zealandia is the fishing grounds of a large part of New Zealand's fishing fleet and holds New Zealand's largest natural gas field, the Maui gas field near Taranaki. Concessions for oil exploration in the Great South Basin off the South Island of New Zealand were granted in 2007. Submarine natural resources, for example, iron sands, volcanic Massiverze and iron -manganese nodules.
Geology
The surface of Zealandia consists of continental crust. Their deep location below sea level in comparison to other areas of continental crust they owe the strain that has greatly thinned the crust, so that it is about 20 kilometers thick only and from isostatic reasons not so far looms as other continental crust.
After the solution of Antarctica before 85-130 Ma and of Australia from 60 to 85 Ma Zealandia sank almost entirely or entirely below sea level. Maybe it was before 23 Ma completely under water.
Ma ago, about 25 began the southern part of Zealandia, which is surrounded by the Pacific plate to move compared to the northern part which is surrounded by the Indo -Australian plate to the north. The resulting displacement of geological structures by about 500 km along the Alpine Fault is clearly visible on geological maps. The movement of this plate boundary is responsible for the offset of the New Caledonia Basin in comparison to its original sequel, the Bounty Trough east of New Zealand. The two basins are caused by stalled geratenes seafloor spreading (Failed Rift ).
Volcanism in Zealandia was before, during, and after the detachment of Antarctica and Australia from Gondwana. Although Zealandia has already been removed up to 6000 km from Antarctica, so, the magma underlying the same composition as that of the volcanic operations in Australia and Antarctica. Volcanic formations are widespread, but aside from the large shield volcanoes that formed Banks Peninsula and Otago Peninsula, only small amounts of volcanic products were promoted. Volcanic main phases were in the Upper Cretaceous and Cenozoic in. The cause of the volcanism is unclear, it may be traced back to a mantle plume, to pass over any of the Zealandia, and the hotspot volcanism triggered. In this way, the chain of undersea volcanoes in the Lord Howe seamount chain may have been incurred.
In the Curio Bay Petrified tree trunks and obtained in live position rhizomes form a petrified forest. The trees were related to modern Kauri trees and Araucaria and grew in the Jurassic period 180 Ma, ie before the breakup of Gondwana Zealandias. The forest was covered by volcanic mud flows. During the diagenesis of the sludge, the plant material of silica was replaced and so petrified. Today it is back to the earth's surface, exposed by erosion by the ocean surf.
During the last ice age, a larger part of Zealandia must have passed over the sea surface than is the case today. This is indicated by the discovery of a mammalian jaw in the area of Otago.