Our Region

Flat-topped mountains

Central Otago is often called a “World of Difference” – and part of that difference is caused by what is under the ground – the rocks.

The land mass that is now Central Otago was formed over millions of years and it contains the largest area of metamorphic rock in New Zealand – which affects the landscape. The numerous mountain ranges which border the Rail Trail are mostly “flat-topped” – the Dunstans, the Rock and Pillars, Rough Ridge, and the favourite of artists and photographers - the Hawkduns. Long ago, sedimentary rocks were heated and compressed deep under ground, forming metamorphic schist – we see this rock everywhere in Central, in old cottages and buildings and in the rocky tors scattered along the hilltops. Later, much of the land mass sank under the water and was eroded, forming a flat “peneplain” which was then uplifted, exposing the Otago schist. Later still, within the last 5 million years, the land was compressed sideways between two plates, forming a series of parallel, block-faulted mountain ranges – leaving valleys between, where we cycle. The flat tops on these mountains that we see today are the remains of the peneplain, and they stay flat, because metamorphic schist doesn’t easily erode to form peaks. Oh, and gold was formed during the metamorphic process. Gold is twice the weight of lead and it accumulated in the river valleys for millions of years - awaiting the arrival of the miners.