Following is a list of the more important rivers. For purposes of uniformity, the length of a river is taken to be the distance from the mouth to the farthest point in the system, whether this should happen to bear the same name or that of an affluent, and is inclusive of the estimated course of a river flowing into and emerging from any lake in the system. The discovery in that the beds of rivers in the South Island contained extensive deposits of alluvial gold was of considerable importance in the early economic development of the country.
Many rivers are valuable for recreational activities such as swimming, canoeing, rafting, jet boating, tramping, camping, and picnicking, and with the very successful acclimatisation of freshwater fish, notably trout, rivers now provide exceptionally fine fishing. Lakes —In considering New Zealand's numerous lakes a distinction can be made, especially from the scenic viewpoint, between the lakes of the 2 islands. Surrounded by extremely rugged country the larger lakes of the South Island are distinguished by the grandeur of their alpine settings, while some of the larger ones of the North Island, situated on a volcanic plateau, have their own particular beauty.
The lakes of both islands are of vital importance as reservoirs, for the maintenance of the rivers and streams draining them and as a means of flood prevention, especially where hydro-electric schemes are involved.
Craigslist joliet dating
A series of narrow man-made lakes have been produced in connection with hydro-electric development along some of the rivers. In Lake Benmore, New Zealand's largest artificial lake, was created. It lies on the Waitaki River in North Otago and covers 75 sq km in area and consists of two arms, the main arm being 30 km in length and the Ahuriri Arm 18 km in length. Some particulars of the more important lakes are given in the following table.
This is a region where volcanoes are active and where the Earth's crust has long been buckling and breaking at a geologically rapid rate. The interplay, in the past, of earth movements and erosion has created the sedimentary rocks that cover almost three-quarters of New Zealand.
Land areas that the earth movements have raised have been attacked by erosion, and the sand, mud, shingle, and other debris thus formed has been carried away to the sea, where it has accumulated in great thicknesses to form rocks such as sandstone, mudstone, greywacke, and conglomerate; the shells and other skeletons of sea creatures have accumulated to form thick layers of limestone.
Many of the sedimentary rocks are in distinct layers called strata. Earth movements have later raised them above the sea to form land, and the strata have in many places been tilted and folded by pressure. Seas have advanced and retreated over the New Zealand area many times and these sedimentary rocks represent almost every geological period since the Cambrian see Time Scale.
Their age is revealed by the molluscan shells, foraminifera, and other fossils that they contain, as well as by various radioactive techniques.
As featured in
As well as sedimentary rocks, and volcanic rocks of various ages, New Zealand incorporates in its complex structure schist, gneiss, marble and other metamorphic rocks, and granite, diorite, gabbro, serpentine, and other intrusive igneous rocks. Most of these metamorphic and intrusive rocks are hundreds of millions of years old. The metamorphic rocks were developed by the action of heat and pressure on the thick sediments up to tens of thousands of metres deposited in huge, elongated sea basins geosynclines , which continued to sink as the deposits accumulated. When these geosynclines were slowly compressed during major mountain-building episodes the deeper sediments were subjected to great pressure and shearing stress, which caused new minerals and structures to develop, changing the sediments into metamorphic rocks.
The granites and other intrusive rocks are coarsely crystalline, and are usually considered to have intruded into the outer crust in a molten state during mountain building; some, however, may be the products of an intense metamorphism of sediments.
Geological History —Evidence of the earliest-known events in New Zealand's history is given by ancient rocks in Nelson, Westland, and Fiordland that were formed in the early Paleozoic era, perhaps as long as million years ago some in Westland may be older. They include thick, geosynclinal sedimentary rocks. This suggests that a large land mass existed nearby at that time to yield the great volume of sediments, but little has been deduced about its shape or position. The history of the later part of the Paleozoic era, and the Mesozoic era, is rather better understood.
For a vast span of time from the Carboniferous period—probably until the early Cretaceous period—an extensive geosyncline occupied the New Zealand region. At first, during much of the late Paleozoic time, huge quantities of submarine lava and volcanic tuff were included in the materials that accumulated in the geosyncline, but in the later Permian and Mesozoic times the sediments were mainly sand and mud, derived probably from some land west of present New Zealand; they were compacted into hard greywacke a type of sandstone and argillite hard, dark mudstone.
In the early Cretaceous period one of the main mountain-building episodes in New Zealand's history took place. Although geosynclinal sedimentation continued through the Cretaceous period in eastern New Zealand the geosyncline elsewhere was compressed, and the sediments were intensely crumpled and broken and raised above the sea, probably forming a large, mountainous land mass.
Some of the geosynclinal deposits, now exposed over much of Otago, alpine Westland, and parts of Marlborough Sounds, were metamorphosed into schist and gneiss by high temperatures and the tremendous deforming pressures to which the geosyncline was subjected. The time that has elapsed since the intense folding of the strata in the New Zealand geosyncline in the mid-Cretaceous period may be considered as the later geological history of this country, embracing roughly million years. During the early part of this late history, erosion slowly wore down the mountains that had risen, producing a land of low relief.
Over these worn-down stumps of the Mesozoic mountains the sea gradually advanced, beginning its transgression earlier in some areas than in others. In the early Cretaceous period it began to submerge land in the region of present North Auckland and the eastern margins of the North and South Islands, and thick deposits of mudstone and sandstone accumulated in some parts of these areas.
At the close of the Mesozoic era, and in the very early Tertiary era, land became so reduced in size and relief that little sediment was formed, and only comparatively thin deposits of fine bentonitic and sulphurous muds, and fine white foraminiferal limestone accumulated. In some areas New Zealand's main coal deposits accumulated in swamps on the surface of the old land.
These became buried by marine deposits as the sea continued its transgression in the Eocene period.
- Four New Zealan police shot as gunman opens fire during a drug raid.
- Puhelinnumero Huittinen Sex education Suomi.
- Member login.
- Dating seite kostenlos.
- elite speed dating near New Plymouth New Zeland;
- Dating software freeware deutsch.
- dating place in Gisborne New Zeland;
By the Oligocene period most of the land was submerged, and in shallow waters free of land sediments thick deposits of shell and foraminiferal limestone accumulated. Scattered remnant patches of this Oligocene limestone furnish most of New Zealand's cement and agricultural lime. After the Oligocene submergence earth movements became more vigorous; many ridges rose from the sea as islands, and sank or were worn down again; sea basins formed and rapidly filled with sediments.
We can think of Tertiary New Zealand as an archipelago. A kind of writhing of part of the mobile Pacific margins seems to have gone on. The thick deposits of soft, grey mudstone and sandstone that now make up large areas of the North Island, and some parts of the South Island, are the deposits that accumulated rapidly in the many sea basins, large and small, that developed in the later Tertiary.
- Announcements!.
- Fleshlight Huittinen Suomi Prostituoituja.
- Auckland Man Saul Roberts Receives Home Detention For Defrauding Disability Trust.
Very late in the Cenozoic era—in the Pliocene and Pleistocene periods—one of the greatest episodes of mountain building in New Zealand's history took place. Earth movements became intense, and slowly pushed up the Southern Alps and other main mountain chains, and determined the general shape and size of the present islands of New Zealand.
Much of the movement during this mountain-building period the Kaikoura Orogeny took the form of displacement of blocks of the Earth's crust along fractures called faults.
Users Reviews
The total movements of the Earth blocks adjacent to major faults amounted to thousands of metres. It must have been achieved very slowly, probably by innumerable small movements, each less than a few metres. The New Zealand landscape today in some regions shows well preserved tilted fault blocks bounded by fault-scarps—steep faces hundreds or even thousands of metres high. Fault movements continue to the present day, and have accompanied several major earthquakes of the past century. Many minor but revealing landscape features such as scarplets, fault ponds, and shutter ridges show where movement has been occurring in recent centuries.
Erosion during this time has eaten into the major landscape forms that the earth movements built, carving detailed landscape patterns of peaks, ridges, valleys, and gorges, and the deposition of the debris has built up alluvial plains, shingle fans, and other construction forms. At the coast, waves have driven back the headlands and built beaches, spits, and bars. The Pleistocene period was the time of the Ice Age, and in the high mountains of the South Island glaciers carved deep valleys and carried huge loads of rock, dumping them in the lower parts of the valleys as moraines.
The late Pleistocene glaciers carved the fiords of Fiordland and the basins occupied by most South Island lakes; there were small glaciers also on Ruapehu, where remnants survive, and on Mount Egmont and the Tararua Range. Sea-level changes accompanied the formation and later melting of the land ice, affecting the erosion or deposition of the rivers and thus being responsible for the formation of the many prominent river terraces in this country.
Volcanic activity of the past few million years has played an important part in making the rocks and shaping the landscape of parts of the central and northern North Island. Banks Peninsula, a twin volcanic dome in Canterbury, also achieved much of its growth then. The largest volcanic outpourings of late geological times in New Zealand have been in the region between Tongariro National Park and the Bay of Plenty Coast: andesite lava, scoria, and ash were erupted in the Pleistocene period and later to build the huge volcanoes, Ruapehu, Tongariro, and Ngauruhoe. More than cu km of molten rhyolitic magma was erupted in the form of ignimbrite, pumice, and rhyolite lava, building up the Volcanic Plateau.
This is one of the largest and youngest accumulations of acid volcanic rocks in the world. Mount Egmont is a huge, conical, andesite volcano, with the remnants of two other volcanic cones nearby; all are of Pleistocene age. In the Waikato there are eroded Pleistocene cones of approximately basic andesite composition. The largest is Pirongia, some m high. Auckland city and the area immediately to the south has been the scene of many eruptions of basalt lava and scoria in late Pleistocene and Holocene times; and many small scoria cones can be seen in the locality.
Late Tertiary and Quaternary basaltic eruptions in North Auckland have built lava plateaus and many young cones. Earthquakes are most common in certain geographically limited regions, one of which includes New Zealand. Within these disturbed zones, young fold mountains, oceanic trenches, volcanoes, anomalies in the Earth's gravitational field, and active geological faulting are also usual, and like the earthquakes have their ultimate cause in the internal processes incidental to the major structural development of the Earth, and as yet are imperfectly understood.
The seismically active zones define the margins of a system of stable blocks or plates which are not completely inactive, but experience large earthquakes only infrequently, and are thought to be the primary units of the Earth's crust. Two of these units, the Pacific and Indian Plates, abut in the vicinity of New Zealand, forming a triple junction with a third, the Antarctic Plate, south of Macquarie Island. As a result of thermally generated convective movements in the deeper levels of the earth, relative displacement of the plates is occurring and this provides the continuing source of the energy that is intermittently released as earthquakes.
Dating seite kostenlos
Instrumental records have shown that at the time of an earthquake large shearing movements take place at the source. It seems probable that all major earthquakes are the result of the breakage of rock under strain, but other factors such as the presence or absence of liquid in the pores and fractures of the rock are also of primary importance in determining the time and place at which a shock occurs. In large shallow earthquakes a rupture may appear at the surface, forming or renewing movement on a geological fault.
In regions where the majority of earthquakes are very shallow, such as California, there is a tendency for the earthquake origins to cluster near geological fault traces, but in regions where there is deeper activity, such as New Zealand, this is not so. For example, there is little activity near the Alpine Fault, which stretches for some km from Milford Sound to Lake Rotoiti, and is considered one of the world's largest and most active faults. Conversely, instances of fault movement that have not been accompanied by earthquakes are known. Practical assessments of earthquake risk must therefore be based upon the statistics of known earthquake distribution and the broader geological setting of the origins.
New Zealand Seismicity —Compared with some other parts of the Pacific margin, such as Japan, Chile, and the Philippines, the level of seismic activity in New Zealand is moderate. It may be roughly compared with that prevailing in California. A shock of Richter magnitude 6 or above occurs on the average about once a year, one of magnitude 7 or above once in ten years, and one of about magnitude 8 perhaps once a century, but in historic times only one shock the south-west Wairarapa earthquake in is known to have reached this magnitude.
Other natural disasters and accidents are together responsible for more casualties than earthquakes, the most serious seismic disasters in New Zealand having been the Hawke's Bay earthquake of in which deaths occurred, and the Buller earthquake of in which there were The total resulting from all other shocks since is less than 15 deaths. The last earthquake to cause deaths occurred at Inangahua in , when 3 people died. Regarded broadly, the zone of seismicity within which New Zealand lies extends continuously from the triple junction south of Macquarie Island to Samoa. When looked at more closely, breaks in continuity and changes in the character of the activity become apparent.
There are changes in direction, in the positional relationship of the deeper and shallower activity, and in its association with the other geophysical and geological features of the region. Within New Zealand itself, at least two separate systems of seismic activity can be distinguished. Less clearly defined activity covers the remainder of the two main islands, and extends eastwards from Banks Peninsula to include the Chatham Islands.
Shallow earthquakes, which are the most numerous, originate within the Earth's crust, which in New Zealand has an average thickness of some 35 km. These shocks are responsible for almost all damage to property, and now and in the past they have been widely scattered throughout the country.
In historically recent times, the Main and Fiordland Seismic Regions have been significantly more active than the rest of New Zealand, but neither the Central Seismic Region that lies between them nor the Northern peninsula has been free from damaging shocks. The details of the present pattern are not necessarily unchanging, and could alter significantly after the occurrence of a major earthquake. Because of this, because of the broader geophysical setting, and because of the distance to which the effects of a large earthquake extend, it would be highly imprudent to treat any part of New Zealand as free from the risk of serious earthquake damage.
Many active regions of the Earth have only shallow earthquakes, but in others shocks have been known to occur at depths as great as km below the surface.
Bengali New Zealand Matrimony
It is thought that these deep shocks originate within the edges of crustal plates that have been drawn down or thrust beneath their neighbours. Such deep events are common in both the Main and Fiordland Seismic Regions of New Zealand, but their relative positions with respect to the shallow activity and to other geophysical features are rough mirror images. This is believed to indicate that in the North Island, the edge of the Pacific Plate lies below that of the Indian Plate, while in the south of the South Island the Pacific Plate is uppermost and the Indian Plate has been thrust beneath it.