The Geological and Biological Origins of New Zealand
New Zealand has a unique landscape with many animals and plants that are native only to itself. The purpose of this essay is to discuss the geological history of the formation, as well as the biological origins, of New Zealand. It will also discuss how the major land-forming processes of volcanism, glaciation and tectonic plates have shaped the country and defined it’s native flora and fauna. Eighty-five million years ago the landmass now known as New Zealand broke away from the supercontinent Gondwana. This massive landmass moved into the Pacific Ocean and eventually became isolated in the Southern Hemisphere; it has had an ever-changing shape with it’s own often unique species' of plant and wildlife. By investigating the geological origins and land-forming processes of New Zealand we can piece together New Zealand’s creation and growth and learn how these processes, and the separation and isolation, have defined New Zealand’s flora and fauna.
General background and historical information of the formation of New Zealand Gondwana and its life forms
New Zealand's oldest known rocks are about 680 million years old and were once part of the supercontinent Gondwana. The sediment from these rocks eroded into the deep sea-basins, eventually hardened into rock, and then folded and was uplifted into mountains because of the plate tectonic movements of the Earth, forming part of the Rangitata landmass. (McKinnon, Bradley, & Kirkpatrick, 1997 p. 3). Eighty million years ago the Rangitata landmass broke away from Gondwana and headed east on the Pacific Tectonic Plate. A fragment of this landmass eventually became New Zealand. As the landmass slowly drifted away, the Tasman Sea formed between the continents. “About 26 million years ago the boundaries of Pacific and Indo-Australian Tectonic Plates ran through the New Zealand landmass, marked by the Hikurangi Trench and the Alpine Fault” (McKinnon et al. 1997, p. 4). There was immense tectonic activity along this border, which resulted in volcanoes and uplift, creating mountains and this mountain-building still continues today. In the region of the Hikurangi Trench, the Pacific Plate began to sink under the Australian Plate in a process known as subduction. Eventually the New Zealand landmass became recognisable as two islands when the southern end of the North Island began to sink below the sea pulled down by the Pacific Plate five million years ago (McKinnon et al. 1997, p. 4). At the time of the breakaway from Gondwana, the flora and fauna were the same as those in other parts of the supercontinent. The Te Ara (n.d) website compares Gondwana to an ark, sailing away from Australia with a cargo of Gondwana plants and animals. The main plants were those such as conifers and ferns. Trees such as kauri and beech and flowering plants were just evolving. The fauna included tuatara, dinosaurs, insects, frogs and birds, including the ancestors of the flightless kiwi and moa (McKinnon et al. 1997, p. 3) The New Zealand landmass had already broken away from Gondwana and was surrounded by sea when the marsupials evolved 70 million years ago. For some time birds and seeds could travel across the sea. Ancestors of some of New Zealand’s native birds, such as the wren and wattlebirds species found only in New Zealand may have arrived at this time, as well as the short-tailed bat blown in from Australia. However when the Tasman Sea ceased to keep widening 60 million years ago, '‘chance colonisations became extremely rare'’ (McKinnon, Bradley, & Kirkpatrick, 1997, p. 4). Examples of Rock in NZ
Sedimentary, metamorphic and igneous rocks and fossils
Rocks are continually being reworked and recycled over time and by examining these rocks, and also fossils, we can assess the type of rock or age of a fossil and then compare this to the geological processes happening at the time. By looking at a rock that is...
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