Beginning in the west, the geography of Otago consists of high alpine mountains. The highest peak in Otago (and highest outside the
Aoraki / Mount Cook area) is
Mount Aspiring / Tititea, which is on the
Main Divide. From the high mountains the rivers discharge into large glacial lakes. In this part of Otago
glacial activity – both recent and very old – dominates the landscape, with large
U-shaped valleys and rivers which have high sediment loads. River flows also vary dramatically, with large flood flows occurring after heavy rain. Lakes
Wakatipu,
Wānaka, and
Hāwea form the sources of the
Clutha River / Mata-Au, the largest river (by discharge) in New Zealand. The Clutha flows generally to the southeast through Otago and discharges near
Balclutha. The river has been used for
hydroelectric power generation, with large dams at
Clyde and
Roxburgh. , where
Roaring Meg joins the
Kawarau River, in central Otago area, looking southwest.
State Highway 8 runs across the photo (only visible in the right half), crossing the
Clutha River just below centre. is New Zealand's highest mountain outside the
Aoraki / Mount Cook region. The country's fourth-longest river, the
Taieri, also has both its source and outflow in Otago, rising from rough hill country and following a broad horseshoe-shaped path, north, then east, and finally southeast, before reaching the Pacific Ocean. Along its course it forms two notable geographic features – the broad high valley of the
Strath-Taieri in its upper reaches, and the fertile
Taieri Plains as it approaches the ocean. Travelling east from the mountains, the
Central Otago drylands predominate. These are
Canterbury–Otago tussock grasslands dominated by the block mountains, upthrust
schist mountains. In contrast to Canterbury, where the Northwest winds blow across the plains without interruption, in Otago the block mountains impede and dilute the effects of the
Nor'wester. The main Central Otago centres, such as
Alexandra and
Cromwell, are found in the intermontane basins between the block mountains. The schist bedrock influence extends to the eastern part of Otago, where remnant volcanics mark its edge. The remains of the most spectacular of these are the Miocene volcanics centred on
Otago Harbour. Elsewhere, basalt outcrops can be found along the coast and at other sites. Comparatively similar terrain exists in the high plateau land of the
Maniototo Plain, which lies to the east of Central Otago, close to the upper reaches of the Taieri River. This area is sparsely populated, but of historical note for its importance during the
Otago gold rush of the 1860s. The townships of
Ranfurly and
Naseby also lie in this area. In the southeastern corner of Otago lies
The Catlins, The Catlins ranges are
strike ridges composed of
Triassic and
Jurassic sandstones,
mudstones and other related sedimentary rocks, often with a high incidence of
feldspar. Fossils of the late and middle Triassic
Warepan and Kaihikuan stages are found in the area. ==Climate==