The geology of New Zealand is noted for its volcanic activity, earthquakes and geothermal areas because of its position on the boundary of the Australian Plate and Pacific Plates. The rocks that now form the continent of Zealandia were nestled between Eastern Australia and Western Antarctica.
The oldest rocks in New Zealand date from mid Cambrian times Maalthough there are older rocks in the Auckland Islands. The lower basement rocks are divided into the "Western Province", consisting mainly of granite and gneissand an "Eastern Province", consisting mainly of greywacke and schist.
The provinces are further divided into terranes — large slices of crust with different geological histories that have been brought together by tectonic activity subduction and strike-slip faulting to form New Zealand. The plutonic basement rocks are subdivided into the HohonuKarameaMedian and Paparoa batholithsthat solidified from magma deep in the crust. The rocks can be matched to similar rocks in Eastern Australia. The Eastern Province sedimentary rocks form the foundation for the rest of New Zealand.
They are mostly composed of greywacke together with argillite. For example, Nelson and Southland used to be Order Geology Personal Statement, as were Marlborough and Otago. In general, the sedimentary basement terranes become younger from West to East across the country, as the newer terranes were scraped off the subducting paleo- Pacific Plateand accreted to the boundary of Gondwana over hundreds of millions of years. The Median Batholith represents a please click for source batholith dividing the Western and Eastern Provinces, and before the separation of Gondwana, stretched from Queenslandthrough what is now New Zealand, into West Antarctica.
It marks the site of a former subduction zone on the edge of Gondwana. They contain sandstone and mudstone derived from volcanic rock, and some limestone.
The Maitai terrane includes the Dun Mountain Ophiolite Beltwhich contains dark serpentinised ultramafic rocks. These rocks form a line split by the Alpine Fault throughout the length of the country that can be detected by the magnetic anomaly it produces. Ophiolites are slices of oceanic crust and magma that have been detached from a subducting plate, and obducted onto the continental crust above the subduction zone.
Personal Statement of Purpose Editing for Graduate School, Medical Residency Examples, Dental Samples, Nursing Intent, Goals, Letter Writing Service, Help. Geology (from the Ancient Greek γῆ, gē, i.e. "earth" and -λoγία, -logia, i.e. "study of, discourse") is an earth science concerned with the solid Earth, the. On Saturday, January 20th, Blackboard will be performing scheduled infrastructure maintenance. While they anticipate no interruptions in service, there may periods of. The geology of New Zealand is noted for its volcanic activity, earthquakes and geothermal areas because of its position on the boundary of the Australian Plate and. ABOUT US. We value excellent academic writing and strive to provide outstanding essay writing services each and every time you place an order. We write essays.
Much of the rocks were deposited as submarine fans. They have different origins, as shown by different chemical compositions and different fossils. Many rocks in the Eastern Province have been metamorphosed into schist, due to exposure to high pressures and temperatures. Rocks grade continuously from greywacke e. New Zealand and New Caledonia represent the visible part Order Geology Personal Statement a portion of continental crustusually referred to as Zealandia.
Then around 83 Ma, Zealandia started to separate from Australia forming the Tasman Seainitially separating from the south. By 75 Ma, Zealandia was essentially separate from Australia and Antarctica, although only shallow seas might have separated Zealandia and Australia in the north.
The landmasses continued to separate until early Eocene times 53 Ma. Zealandia ended up at a pivot point between the Pacific and Australian Plates, with spreading in the south, and convergence in the north, where the Pacific Plate was subducted beneath the Australian Plate.
A precursor to the Kermadec Arc was created. The convergent part of the plate boundary propagated through Zealandia from the north, eventually forming a proto-Alpine Fault in Miocene times 23 Ma. The various ridges and basins north of New Zealand relate to previous positions of the plate boundary. New Zealand is currently astride the convergent boundary between the Pacific and Australian Plates. Over time, the position of the plate boundary has altered.
Around 23 Ma, the convergent plate boundary formed Northland. Around 10 Ma, the Coromandel Ranges were formed. The Southern Alps are quite recent, only forming in the last 10 million years. Because New Zealand straddles a plate boundary, it is tectonically active. The Marlborough Sounds are known for their sunken mountain ranges.
As Wellington click here, and Marlborough sinks, Cook Order Geology Personal Statement is being shifted further south. Deep earthquakes originate in the subducted plate. Because the Pacific Plate is subducting under the eastern side of the North Island, there are frequent deep earthquakes east of a line from the Bay of Plenty to Nelson the approximate edge of the subducted platewith the earthquakes Order Geology Personal Statement deeper to the west, and shallower to the east.
Because the Australian Plate is subducting under the Pacific Plate in Fiordlandthere are frequent deep earthquakes near Fiordland, with the earthquakes being deeper to the east and shallower near the west. Order Geology Personal Statement are few deep earthquakes along the Southern Alpsbecause the two sides largely slide past each other.
Shallow earthquakes are caused by stresses in the top plate. However, Northland, Waikatoand Otago are relatively stable. Canterbury had been without a major earthquake in recorded history until the M w 7. The Encyclopedia of New Zealand. An allochthon is land that formed elsewhere, and slid on top of other land in other words, the material of an enormous landslide. Much of the land of Northland and East Cape were created in this manner. Northland-East Cape was an undersea basin. Much of the land that now forms Northland-East Cape was higher land to the Northeast composed of rocks formed 90—25 Ma.
Layers of rocks were peeled off the higher land, from the top down, and slid Southwest under the influence of gravity, to be stacked the right way up, but in reverse order. The last rocks to be slid across were slabs of oceanic crustmainly basalt. Widespread volcanic activity also occurred 23—15 Maand is article source with the foreign rocks. East Cape was later separated from Northland and moved further south and east to its present position.
Swamps became widespread, forming coal. The land subsided further, and marine organisms produced limestone deposits. Many of New Zealand's limestone deposits were formed in relatively cool seas. When a plate is subducted under another plate, it causes melting in the mantle, the layer of the earth below the crust, and produces a volcanic arccomposed of mainly andesitic and rhyolitic volcanoes in New Zealand, but often widely varying in composition depending on the type of island arc.
Andesitic eruptions tend to form steep stratovolcanoesincluding mountains such as RuapehuTongariro and Taranakiislands such as Little BarrierWhite and Raoul Islandsor submarine seamounts like Monowai Order Geology Personal Statement.
Rhyolitic eruptions with large amounts of water tend to cause violent eruptions, producing calderassuch as Lake Taupo and Lake Rotorua. Basaltic volcanoes tend to form at intra-plate hot spots.
Basaltic eruptions tend to be fairly placid, producing scoria cones Order Geology Personal Statement lava flows, such as the volcanic cones in the Auckland volcanic fieldalthough Mount Tarawera 's violent eruption was an exception. The South Island has no currently active volcanoes. However, in the late Cretaceous —65 Mathere was widespread volcanic activity in Marlborough, West Coast, Canterbury and Otago; and in Eocene times 40 Mathere was volcanic activity in Oamaru.
The most well known Miocene volcanic centres are the Otago and Banks Peninsulas.
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The Otago Peninsula near Dunedin was built up by a series of mainly basaltic intra-plate volcanic eruptions in Miocene times 16—10 Ma. This has resulted in the formation of Port Chalmers. Banks Peninsula near Christchurch was built from two mainly basaltic intra-plate volcanoes in Miocene times 12—6 Ma and 9. click
Southland's Solander Islands were active around 1 to 2 million years ago. The North Island is home to both old and currently active volcanoes. Over time, volcanic activity has moved south and east, as the plate boundary moved eastward, and the place where subduction click from the Pacific Plate to the Australian Plate moved south.
A volcanic arc became active to the west of the current land in Northland in Miocene times 23 Maand gradually moved South down to New Plymouthwhere Taranaki is still active. It produced mainly andesitic strato-volcanoes.
The Northland volcanoes include the volcanoes that produced the Waipoua Plateau site of Waipoua Forestwith large Kauri trees and Kaipara volcano. The Waitakere volcano 22—16 Ma has mainly been eroded, but conglomerate from the volcano forms the Waitakere Ranges Order Geology Personal Statement, and produced most of the material that makes up the Waitemata sandstones and mudstones.
Lahars produced the coarser Parnell Grit. Notable visible volcanoes in the Waikato include Karioi and Pirongia 2. Taranaki Order Geology Personal Statement a perfectly formed andesitic strato-volcano, that last erupted in The volcanoes off the West coast of the North Island, together with Taranaki and the Tongariro Volcanic Centre, are responsible for the black iron sand on many of the beaches between Taranaki and Auckland.
Shortly after 18 Maa volcanic arc developed further east to create the Coromandel Ranges and undersea Colville Ridge. The initial activity was andesitic, but later became rhyolytic 12 Ma.
In the Kauaeranga Valleyvolcanic plugs remain, as does a lava lake that now forms the top of Table Mountain. Active geothermal systemssimilar to those that now exist near Rotoruawere present around 6 Ma, and produced the gold and silver deposits that were later mined in the Coromandel gold rush.
Later 5—2 Mavolcanic activity moved further south to form the Kaimai Range. Activity was initiated around 2 Ma, and continues to this day. The Tongariro Volcanic Centre is composed of andesitic volcanoes, while the areas around Taupo and Rotorua are largely rhyolitic.
The Tongariro Volcanic Centre developed over the lastyears and contains the active andesitic volcanic cones of Ruapehu, Tongariro, and Ngauruhoe really a side cone of Tongariro. Ruapehu erupts about once a decade, and while the eruptions cause havoc for skiers, plane flights and hydroelectric dams, the eruptions are relatively minor.
However, the sudden collapse of the crater wall caused major problems when it generated a lahar inthat destroyed a rail bridge, and caused deaths at Tangiwai. The last significant eruption was — Ngauruhoe last erupted — Lake Taupothe largest lake in the North Island, is a volcanic calderamore info for rhyolitic eruptions about once every 1, years.
The largest eruption in the last 65, years was the cataclysmic Oruanui Order Geology Personal Statement 26, years ago, producing cubic kilometres of magma. The most recent eruption, around AD was Order Geology Personal Statement a major event, the biggest eruption worldwide in the last 5, years. The eruption caused a pyroclastic flow that devastated the land from Waiouru to Rotorua in 10 minutes.
The Okataina volcanic centre, to the East of Rotorua, is also responsible for major cataclysmic rhyolitic eruptions. The last eruption, of Tarawera and Lake Rotomahana inwas a relatively minor eruption, which was thought to have destroyed the famous Pink and White Terracesand covered much of the surrounding countryside in ash, killing over people. In researchers rediscovered the locations of the Pink and White Terraces using a forgotten survey from Many lakes around Rotorua are calderas from rhyolitic eruptions.
For example, Lake Rotorua erupted around 13, years ago.