Mountains dominate large areas of the New Zealand landscape. About 60% of the South Island is covered by ranges with peaks over 1,500 metres high. Some peaks in the Aoraki/Mt Cook region of the central Southern Alps are more than twice this height.
The highest peaks
Aoraki/Mt Cook, at 3,724 metres high, is New Zealand’s tallest mountain. It is 230 metres higher than its nearest rival, Mt Tasman.
The South Island also has:
- 23 named peaks over 3,000 metres high
- more than 3,000 glaciers or permanent snow patches
- many lakes of glacial origin (including seven of the 10 largest lakes in the country)
- ice-carved fiords
- the deepest and longest cave systems in the Southern Hemisphere and the best example of glaciated karst terrain (with limestone formations such as fissures, sinkholes, and underground streams), both in Kahurangi National Park.
The Southern Alps
The Southern Alps stretch for 500 kilometres, from Nelson Lakes National Park in the north-east to near the entrance of Milford Sound in the south-west. Made of greywacke sandstone in the east and schist in the west, they are by far the highest, longest, and most heavily glaciated chain of mountains in the country.
All of New Zealand’s peaks over 3,000 metres are in the Southern Alps. They also contain all the larger high snowfields (névés) and all remaining glaciers that extend down to the floors of major valleys.
In the west, the mountains end steeply and abruptly at the line of the Alpine Fault. To the east they spread further, with ranges and basins covering a large area of mostly high-country lands.
Effect on climate
For thousands of kilometres, the Southern Alps are the only significant mountain barrier to the moist westerly winds of the Southern Ocean. This causes the range to generate the most extreme climatic conditions in New Zealand. There is a very high-rainfall zone to the west, and often drought-prone regions to the east.
The Fiordland ranges
South of the Southern Alps is the steep maze of the Fiordland ranges, which continue for 220 kilometres to the south-west corner of the island. These ranges gradually taper from high glaciated peaks in the north (Mt Tūtoko, 2,723 metres, and Mt Madeline, 2,536 metres) to summits between 1,500 metres and 1,000 metres, south of Dusky Sound.
The different geology of these ranges has produced strikingly different landforms. The very hard rocks of the sheer-walled valleys and fiords do not show the weathering and erosion seen in the Southern Alps.
The Kaikōura ranges
In the north-east of the South Island, the high Inland and Seaward Kaikōura ranges splinter eastwards from the Southern Alps.
Explorer Julius Haast wrote of the Tasman Glacier, ‘As far as the eye could reach everywhere snow and ice and rock appeared around us, and in such gigantic proportions that I sometimes thought I was dreaming, and instead of being in New Zealand I found myself in the Arctic or Antarctic mountain regions.’ 1
The Inland Kaikōuras are dominated by the highest mountains in the country north of the Aoraki/Mt Cook region. These are Tapuae-o-Uenuku (2,884 metres) and Mt Alarm (2,877 metres).
The Seaward range includes the highest peaks near New Zealand’s eastern coast – Manakau (2,608 metres) and Te Ao Whēkere (2,590 metres).
The north-west ranges
In the north-west of the South Island are the Paparoa, Victoria and north-west Nelson ranges. They are not as high as other prominent mountain regions, but they contain New Zealand’s oldest sedimentary and volcanic rocks, its oldest fossils, its northernmost glaciated valleys, and some of the most dramatic landslides.