Granite boulders, Waitutu, Fiordland National Park

The Waitutu Forest makes up the southeastern extremity of Fiordland National Park, New Zealand’s largest national park. In contrast to the famous glacially-shaped landscape of most of the rest of the park further north, the Waitutu Forest is situated on a series of raised coastal terraces that slope gradually down to the wild and remote southern coast. These terraces also contrast with much of the rest of the park in that they are underlain by relatively soft sedimentary rocks whereas most of the steeper mountainous country elsewhere in the park is underlain by granite, a much harder and more resistant metamorphic rock.

The Waitutu River drains southward from Lake Poteriteri, and over the course of thousands of years it and other local rivers have transported large quantities of granite to the coast from their mountainous upper catchments. This has resulted in granite being widespread along the park’s southern beaches, despite the fact that it doesn’t occur naturally in any of the local bedrock. These resistant boulders have been beautifully rounded and worn smooth from being tumbled over many kilometres of riverbed on their way downstream, a grinding process that is continued by waves and tides once they reach the coast. These granite boulders, some over half a metre in diameter, are especially abundant around the mouth of the Waitutu River where many thousands of them lie at the top of the beach.