New Zealand Geography Part II

Triassic and Jurassic formations can be followed continuously throughout the North Island, from the Bay of Plenty to Wellington. During the long orogenetic stasis which lasted from the Cretaceous to the Miocene erosion deeply attacked the emerged areas: the enormous quantity of detrital material produced progressively filled numerous sedimentation basins, also burying the vegetation and thus starting the carbonization process to which the litanthracs and lignites are due New Zealanders. After the orogenetic phases of the upper Cenozoic-Pleistocene already mentioned, and fundamental for the structural order of New Zealand, a country located in Oceania according to, the current conformation was reached during the Neozoic with the filling of the depressions between the main reliefs and the formation of the coastal plains; while in the North Island volcanic activity persisted, the action of the imposing glaciers that covered much of it during the glacial periods was predominant for the shaping of the southern island. New Zealand has a shape that recalls that of the Italian “boot”; extends in the SW-NE direction for approx. 1500 km: the west and east coasts, however, are almost never more than 200 km away. The coasts, generally very articulated, extend for 4800 km; very picturesque is the stretch of the west coast of the South Island to the S of Big Bay, carved by deep fjords. The North Island is particularly indented along the strait Auckland peninsula, which juts out to the NW for approx. 330 km, welded to the rest of the island by a thin isthmus, between the bays of Waitemata to the E and Manukau to the West, on which the main city of New Zealand, Auckland, was built. Also an excellent natural port is Port Nicholson, which the capital overlooks. The North Island has a tormented and varied morphology: in the center, all around the basin of Lake Taupo, there is a plateau of 400-600 m, an ancient limestone-arenaceous massif flattened by erosion and covered by lava expansions and by pyroclastic deposits; numerous volcanic cones rise there, also grouped in chains like the Hauhungaroa mountains. Mostly they are considered active, like Ruapehu (2797 m, the highest peak of the North Island), Ngauruhoe (2291 m) and Tongariro (1968 m); certainly off is the Egmont (2518 m), which rises isolated dominating the Taranaki peninsula on the west coast. In this complex volcanic region there are numerous manifestations of secondary volcanism, from fumaroles to solfataras, from geysers to the thermal springs.

For the rest, the backbone of the island consists of a succession of short chains with maximum heights varying between 1400 and 1750 m, arranged on the eastern side and directed according to the general alignment of the New Zealand relief, i.e. from SW to NE, from the Tararua Range to the Raukumara Range; the long appendage of the Auckland peninsula presents a disjointed relief with a hilly aspect that does not exceed 800 meters. Much more compact and homogeneous is the South Island, crossed along the western edge by the mighty system of the New Zealand Alps, particularly high in the central section with numerous peaks over 3000 m, the highest of which, Mount Cook, touches 3754 m. Minor ridges branch off from the main chain, both towards the SW until forming the steep buttresses of the fjord-like coasts, and towards the S until it disappears into a series of modest hills near the south-eastern coast. AN the New Zealand Alps break up into a series of short ranges separated by long longitudinal valleys which in the northeastern extremity, where they are partially submerged, give rise to a characteristic rías landscape . The eastern side of the New Zealand Alps slopes slowly, extinguishing itself in the wide coastal plain of Canterbury, about thirty kilometers deep, approx. 150. On the Strait of Foveaux the other major plain of the island faces, bordered to the NE by modest hills, beyond which a new flat area opens up to the Otago peninsula. Beyond the Strait of Foveaux, the island of Stewart presents modest reliefs (maximum height is Mount Anglem, 980 m), partly of a volcanic nature, to the N, and the rest of granite. The other main New Zealand islands also show a more or less evident volcanic origin: thus, entirely volcanic are the Auckland and Campbell, all with evident traces of glacial modeling, and the Kermadecs, the largest of which, Raoul Island, presents still some active secondary volcanism, while in the Chatham the Cenozoic volcanic buildings rise no more than 300 m above a paleozoic schist base.

New Zealand Geography 2