The South Island, with an area of , is the largest landmass of New Zealand; it contains about one-quarter of the New Zealand population and is the
world's 12th-largest island. It is divided along its length by the
Southern Alps, the highest peak of which is
Aoraki / Mount Cook at , with the high
Kaikōura Ranges to the northeast. There are eighteen peaks of more than in the South Island. The east side of the island is home to the
Canterbury Plains while the western side is renowned for its rough coastlines in
Fiordland and along the
West Coast, a very high proportion of native
bush, and
Fox and
Franz Josef Glaciers. The mountains of the South Island are exposed to prevailing westerly winds from the Tasman Sea, leading to high
orographic rainfall and the creation of streams and rivers. These contribute to erosion, and together with continuing uplift and the effects of glaciation create vast quantities of gravel and
loess. Glaciation, rivers and gravels have formed the
Canterbury Plains and other South Island flood plains. Most of the loess has formed on the eastern side of the South Island, because of the prevailing winds.
Geology During the
Last Glacial Period when sea levels were over 100 metres lower than present day levels, the North and South Islands were connected by a vast coastal plain that formed at the
South Taranaki Bight. Similarly, the South Island and
Stewart Island were connected by coastal plains that covered modern-day
Foveaux Strait. During this period, most of the South Island was covered in grassland and glaciers, compared to the woodlands and rainforest that grew in the more temperate North Island. Sea levels began to rise 7,000 years ago, eventually separating the islands and linking the
Cook Strait to the
Tasman Sea. There is movement of around per year along the Alpine Fault, very fast by global standards. This is mostly
strike-slip (sideways) movement, with the
Tasman district and
West Coast moving north and
Canterbury and
Otago moving south. The last major earthquake on the Alpine Fault was in about 1717 AD with a great () earthquake magnitude of ± 0.1. The probability of another one occurring before 2068 was estimated at 75 percent in 2021. However, compression also occurs because there is 11° of convergence at the boundary. For most of the length of the Alpine Fault, the compression forces the
continental crust of the Pacific plate up and over the continental crust of the Indo-Australian plate, creating uplift of per year in different places, and forming the
Southern Alps. This uplift has been occurring for at least 5 myr, leading to a total uplift of over the period, although almost all of this is lost to erosion. From
Fiordland south, the Indo-Australian plate
subducts beneath the Pacific plate, with the boundary between the two plates forming the
Macquarie Ridge complex extending to the south of New Zealand. Some of New Zealand's major earthquakes have occurred in the South Island. The
1929 Murchison earthquake caused landslides and widespread damage to roads, bridges and buildings and resulted in 17 deaths. The
Inangahua earthquake occurred on the Alpine Fault in 1968. It killed three people and caused widespread damage to roads, railway tracks and other infrastructure. On 4 September 2010, the South Island was struck by
a 7.1 magnitude earthquake that caused extensive damage, several power outages, and many aftershocks. Five and a half months later, the 6.3 magnitude
22 February Christchurch earthquake caused far more damage in Christchurch, resulting in 181 deaths. This quake was centred closer at
Lyttelton, and shallower than the prior quake, consequently causing extensive damage. There were no fatalities in the
Seddon earthquake of 2013, but it caused damage to buildings in Wellington. In 2016 the
Kaikōura earthquake caused the closure of State Highway 1 between Picton and Waipara and the Main North Line of the railways. Two people died.
Natural geographic features Southern Alps The Southern Alps (officially Southern Alps / Kā Tiritiri o te Moana) are a range of mountains that extend for approximately northeast to southwest along much of the length of the South Island. They were created by the meeting of the Pacific and Indo-Australian tectonic plates. The range includes the South Island's 'Main Divide', which separates the water catchments of the more heavily populated eastern side of the island from those on the
West Coast. is the tallest mountain in New Zealand. The tallest peak of the Southern Alps is
Aoraki / Mount Cook, the highest point in New Zealand at . The Southern Alps include sixteen other points that exceed in height. The mountain ranges are bisected by glacial valleys, many of which on the eastern side are infilled with glacial lakes, including
Lake Coleridge in the north and
Lake Wakatipu in Otago in the south. Settlements within the Southern Alps include
Maruia Springs, a spa near
Lewis Pass, the town of
Arthur's Pass, and
Mount Cook Village. Major crossings of the Southern Alps in the New Zealand road network include Lewis Pass (
SH 7),
Arthur's Pass (
SH 73),
Haast Pass (
SH 6), and the road to
Milford Sound (
SH 94). The
TranzAlpine train operates on the Midland Line between Greymouth and Christchurch, crossing the Southern Alps at Arthur's Pass.
Glaciers Most of New Zealand's
glaciers are in the South Island, generally found in the Southern Alps near the Main Divide. According to inventories conducted in the late 1970s and 1980s, the Southern Alps contained over 3,000 glaciers larger than one hectare. About a sixth of these glaciers covered more than 10 hectares. These include the
Fox and
Franz Josef glaciers on the West Coast, and the
Tasman,
Hooker,
Mueller and
Murchison glaciers in the east. The Tasman Glacier is the longest, reaching in length. It has retreated from a recent maximum of in the 1960s. featuring
Mount Pembroke Fiords and lakes The South Island has 15 named maritime
fiords, which are all located in the southwest of the island in a mountainous area known as
Fiordland. The spelling 'fiord' is used in New Zealand rather than 'fjord', although all the maritime fiords have the word '
Sound' in their name instead. (The
Marlborough Sounds, a series of deep indentations in the coastline at the northern tip of the South Island, are in fact
rias, drowned river valleys.) The South Island has eight of New Zealand's 10 biggest lakes, some of which are fiords that became dammed. Much of the higher country in the South Island was covered by ice during the
glacial periods of the last two million years. Advancing glaciers eroded large
steep-sided valleys and often formed
moraines, accumulations of rocks and soil that acted as natural dams. When the glaciers retreated, they left basins that are now filled by lakes.
Lake McKerrow / Whakatipu Waitai to the north of
Milford Sound / Piopiotahi is a fiord with a silted-up mouth.
Lake Manapouri has fiords as its west, north and south arms.
Lake Te Anau has three western arms, which are fiords (and are so named).
Lake Wakatipu fills a large glacial valley, as do lakes
Hakapoua,
Poteriteri,
Monowai and
Hauroko in the far south of Fiordland. Lake Hauroko is the deepest (462 m) lake in New Zealand, and one of the deepest lakes in the world. The water level of most glacial lakes in the upper parts of the
Waitaki and
Clutha / Mata-Au rivers is controlled for electricity generation. Hydroelectric reservoirs are common in
South Canterbury and
Central Otago. The largest of these is
Lake Benmore, an artificial lake created in the 1960s on the
Waitaki River. Millions of years ago in the
Miocene, Central Otago had a huge lake –
Lake Manuherikia. It slowly filled in with mud, and
fossils of plants, fish, birds and crocodiles have been found there. A group of fossils from the ancient lake that has been studied is known as the
St Bathans fauna. is roughly circular, with many bays and two deep harbours.
Volcanoes There are
extinct volcanoes in the South Island, all located on the east coast.
Banks Peninsula forms the most prominent of these volcanic features. The peninsula comprises the eroded remnants of two large
shield volcanoes. These formed due to intraplate volcanism between about eleven and eight million years ago (
Miocene) on a continental crust and together are known as the
Banks Peninsula Volcano complex. The peninsula formed as offshore islands, with the volcanoes reaching to about 1,500 m above sea level. Two dominant craters formed
Lyttelton / Whakaraupō and
Akaroa Harbours. The portion of the crater rim lying between Lyttelton Harbour / Whakaraupō and Christchurch city forms the
Port Hills.
Otago Harbour was formed from the drowned remnants of a giant
shield volcano (the
Dunedin Volcano) centred close to what is now the town of
Port Chalmers. The remains of this violent origin can be seen in the
basalt of the surrounding hills. The last eruptive phase ended some ten million years ago, leaving the prominent peak of
Mount Cargill.
Timaru was constructed on rolling hills created from the lava flows of the extinct Mount Horrible, which last erupted many thousands of years ago.
Climate The climate in the South Island is mostly
temperate. The mean temperature for the South Island is . January and February are the warmest months, while July is the coldest. Historical
maxima and minima are in
Rangiora, Canterbury, and in
Ranfurly, Otago. Conditions vary sharply across the regions, from extremely wet on the
West Coast to
semi-arid in the
Mackenzie Basin of inland Canterbury. Most areas have between of
rainfall annually, with the most rain along the West Coast and the least rain on the East Coast, predominantly on the
Canterbury Plains.
Christchurch is the driest city, receiving about of rain per year, while
Invercargill is the wettest, receiving about . The southern and south-western parts of South Island have a cooler and cloudier climate, with around 1,400–1,600 hours of
sunshine annually; the northern and north-eastern parts of the South Island are the sunniest areas and receive about 2,400–2,500 hours.
Biodiversity and conservation , a mountain parrot Several bird species are
endemic to the South Island. They include the
kea,
great spotted kiwi,
Okarito brown kiwi,
South Island kōkako,
South Island pied oystercatcher,
Malherbe's parakeet,
king shag,
takahē,
black-fronted tern,
South Island robin,
rock wren,
wrybill, and
yellowhead. Many South Island bird species are now
extinct, mainly due to hunting by humans and predation by mammals introduced by humans. Extinct species include the
South Island goose,
South Island giant moa,
Haast's eagle and
South Island piopio. The
South Island kōkako is also likely to be extinct. Nine of New Zealand's
thirteen national parks are in the South Island. They are known for their scenery and geographic features, such as the
Pancake Rocks in
Paparoa National Park, and are popular recreation and tourism areas.
Arthur's Pass National Park, established in 1929, is the oldest.
Fiordland National Park (established 1952) is New Zealand's largest and one of the largest in the world.
Kahurangi National Park, established in 1996, is the newest and the country's second-largest.
Abel Tasman National Park is New Zealand's smallest, at 225 km2.
Te Wāhipounamu, in the south-west corner of the island, is a
World Heritage Site that incorporates
Westland Tai Poutini National Park,
Aoraki / Mount Cook National Park,
Mount Aspiring National Park and Fiordland National Park. Inscribed on the World Heritage List in 1990, it covers . It is thought to contain some of the best modern representations of the original
flora and
fauna present in
Gondwanaland, one of the reasons for listing as a World Heritage Site. The Conservation Act 1987 defines a conservation park as an area with predominantly natural systems, managed to maintain protection of ecosystems and historical resources while also providing visitor access. Pre-existing forest parks were transferred to the Department of Conservation in 1987 and became ‘conservation parks’, but have retained the designation ‘forest park’. Conservation and forest parks have a less stringent level of protection than national parks and are used for a wide variety of recreational and commercial activities. There are five forest parks in the South Island that are on public land administered by the Department of Conservation:
Mount Richmond Forest Park in Marlborough,
Craigieburn,
Hanmer and
Lake Sumner Forest Parks in Canterbury, and
Victoria Forest Park in the West Coast region. In addition to forest parks, there are a number of conservation parks in the South Island, including:
Ahuriri,
Hakatere,
Ruataniwha and
Te Kahui Kaupeka Conservation Parks in Canterbury;
Oteake Conservation Park in Waitaki;
Te Papanui and
Hāwea Conservation Parks in Otago; and
Eyre Mountains / Taka Ra Haka and
Catlins Conservation Park in Southland. == Demographics ==