Story: Otago region
Page 2 – Geology and landscape
Otago is dominated by ranges and basins that stretch east from the Southern Alps, across Central Otago, and to the ocean at Palmerston and Waikouaiti. The Taieri River, the Shag River (Waihemo) and the Clutha and its tributaries drain the greatest part of this block of land.
Erosion and uplift
Central Otago is a massive block of schist (metamorphosed greywacke), part of the 80-million-year-old Zealandia continent, whose surface was eroded over 60 million years and then uplifted in the last 2 million years. The uplift in Central Otago was not as dramatic as that which produced the Southern Alps, but it reactivated faults, producing the alternating ranges and basins found across the region.
The rivers were established before the land was uplifted, and in places – notably between Queenstown and Cromwell, Cromwell and Clyde, and Alexandra and Millers Flat – they have cut gorges into the uplifted rock.
Central Otago tors
Huge castle-like columns of rock up to 20 metres high, tors are schist outcrops on the summits of the Central Otago ranges. They have weathered less rapidly than the surrounding, less resistant schist, which is the basement rock of Central Otago.
Lakes, mountains and coastal plains
To the north-west, the Central Otago block abuts the Southern Alps, where glaciers have gouged the deep valleys that now contain Lakes Wakatipu, Wānaka and Hāwea. Mt Aspiring/Tititea (3,027 metres) is the highest South Island peak outside the Aoraki/Mt Cook area.
Central Otago is flanked to its north-east and south by the alluvial plains of the Waitaki and Clutha rivers, which are at the centre of North and South Otago respectively.
There are three other sub-regions.
- Otago Peninsula and the adjacent mainland area is an old and now extinct volcanic centre – Otago Harbour is the product of valleys formed north-east (lower harbour) and south-west (upper harbour) of the original eruption site near Port Chalmers.
- The Catlins, and indeed most land south of the Clutha, is an old block of sedimentary rock, uplifted by tectonic action. It is related to similar blocks in Southland such as the Hokonui Hills.
- In North Otago, the hill country along the Waitaki River valley is greywacke, but not metamorphosed into schist as in Central Otago. North Otago also has limestone deposits.
Landforms and people
Otago’s geology and landforms have shaped it in a variety of ways. Gold in the Central Otago rivers brought population and wealth, but later growth – especially in farming – was limited by elevation and by poorer soils than Southland and Canterbury.
Artists, many from Dunedin, have responded powerfully to the Central Otago landscape. Tourists have favoured Central Otago and the lakes district for their dramatic landscapes and unrivalled combination of winter and summer pastimes. In the 2000s Queenstown and Wānaka were among New Zealand’s fastest-growing communities.