The New Zealand landmass lies over the boundary between the Australian and Pacific tectonic plates, which has been active for the last 25 million years. The motion of the plates, and resulting deformation of the earth's crust, have had a strong influence on the shape of the emerged New Zealand land as we know it , as well as on many of its landforms.
   Movements of compression, shear, rotation, spreading in the crust have created mountain ranges, drowned areas, lowland basins and troughs. Volcanism is also a direct consequence of plate tectonic activity.
Image: The Wellington Fault is clearly visible here, cutting across the hills in the left foreground, then forming the western (left) shore of Wellington Harbour, then marking the western (left) side of the Hutt Valley. Photo
copyright NZ Institute of Geological and Nuclear Sciences 2000.
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Other landforms are the more direct consequence of individual earthquakes: scarps and lakes in particular.

Mountains
In New Zealand, mountains are the most visible part of the landscape that results from tectonic activity. Indeed New Zealand's highest mountains in both North and South Islands are part of the Axial Tectonic Belt, which is where most of the country's crustal deformation occurs.

Alpine Fault and Southern Alps
  The Southern Alps rise abruptly from the lowlands and coastal plains of the west coast. The sharp limit between lowlands and mountain is further enhanced by the Alpine Fault, which marks the western edge of the Southern Alps on their entire length.
  The Alpine Fault is the emerged boundary between the Australian and Pacific tectonic plates, which at that place mainly slide past each other. It has been active for the last 25 million years, and in that time its two sides have been displaced by 480 km (300 miles) relative to each other.
   Approximately ten million years ago the plate boundary along the Alpine Fault became compressive. The amount of crustal shortening is estimated at 70 km (43 miles) in the central part of the collision zone, mostly accommodated by overriding of the Australian plate by the Pacific plate.
  Another consequence was the rise of the crust that underlies the Southern Alps, giving birth to the present mountain range. It is estimated that during that time total uplift may have been in excess of 20 km (12 miles). However, due to high rates of erosion the maximum altitude of the Southern Alps may never have been higher than at present (3750 m, 12303').

Lakes
  In areas of steep terrain landslides caused by earthquakes may block rivers and cause the formation of lakes. In New Zealand landslide lakes are relatively numerous: 46 of more than 0.5 km (1640') in length have been identified. The regions where such lakes are most common are eastern North Island, the Wanganui region, the northwest part of the South Island, and the central and southern glacial region.   Not all landslide lakes are permanent: numerous temporary ones were caused by the 1929 Buller earthquake, such as Lake Perrine on the Mokihinui River, and Mud Lake on the Matakitaki River. Similarly, Lake Ngatapa was formed on a tributary of the Mohaka River by the 1931 Hawkes Bay earthquake, and washed out in a flood in 1938.
   The largest and best known of New Zealand's landslide lakes is Lake Waikaremoana, which was formed between 2000 and 3000 years ago. Other well-known landslide lakes include Lake Tutira in Hawkes Bay, Lake Stanley in Kahurangi National park, Lake Matiri north of Murchison, Lake Adelaide in Nelson Lakes National Park, and Lake Lochnagar.

(former) Ahuriri Lagoon, Napier
Ahuriri Lagoon was uplifted by 1 to 1.5 m (3-5') during the 1931 earthquake. About 1300 ha (3500 a) emerged, and a further 1700 have since been reclaimed. This area is now used for farming, and the regional airport.

Wellington
  Wellington lies within the Axial Tectonic Belt, where most of the relative motion between the Pacific and Australian tectinic plates is absorbed, and which continues further north-east through the main axial mountain ranges of the North Island. As a result the area is traversed by several major faults, and the landscape is made of a series of tilted blocks, such as the Rimutaka Ranges.   
   To the east of these blocks frictional drag has caused the creation of lower areas (faulted synclines and anticlines), where are now located Wellington Harbour, Lower Hutt, Upper Hutt and Kaitoke basins.
  Wellington Fault forms the western shore of Wellington Harbour and the north-west boundary of the Hutt Valley, as can clearly be seen from aerial photographs.