Wairere Boulders

The Wairere Boulders are a rock formation at Wairere, in the Hokianga region of northern New Zealand. A geological nature park around the boulders was planned and constructed by Felix and Rita Schaad in 1999. The walkways were built between 2000 and 2003. Wairere Boulders allows visitors to see the large basalt boulders many with rare and spectacular solution features (karst) on the outside that are scattered all over the property of the Schaads, a Swiss couple who emigrated to New Zealand in 1983.

There are several walks ranging from 40 minutes to a maximum walking time of two hours. The gigantic rocks are surrounded by subtropical rainforest. There are some information panels along the track and lots of trees are labelled in Maori and English. The walks are through the Wairere valley which features an unusually large assemblage of basalt rocks.

Part of the farmed area is open for bouldering, which has become more and more popular in recent years. The bouldering area is vast and offers climbing to beginners and experienced boulderers.

The Schaads undertook to create private walkways in highly dangerous surroundings. Therefore, they had to overcome many legal and design obstacles. As Felix was a registered civil engineer, he was able to design the 24 bridges, ramps and stairs and a viewing platform to NZ building standards to guarantee the safety of the visitors.

In March 2000 they got approval and construction started. It took 4 years of hard labour. They dug and metalled all tracks by hand. Also, they singlehandedly built all 25 structures themselves. After rigorous compliance tests by the Far North District Council, the Wairere Boulders finally opened towards end of 2003.

The Wairere Boulders have rolled down the hillsides from an eroding Pliocene basalt lava flow of the Kerikeri Volcanic Group [formerly known as [Horeke basalts]]. Many of the boulders have deep solution basins and fluting formed on their surfaces - a particularly good example of the relatively rare phenomenon of karst formation on basalt (sometimes known as proto-karst). This phenomenon was documented by geologists as early as the 1920s-1940s in Hawaii and New Zealand. Usually karst landforms are formed by solution of calcareous rocks (e.g. limestone and marble) by mildly acidic percolating water. At Wairere, and elsewhere, basalt has been dissolved, probably over a much longer interval of time, by the production of weakly acidic humic acid in the leaf litter that collects around the roots of plants that grow on the top of the boulders, usually beneath a forest canopy. On the top of the boulders this humic acid has etched out solution basins 20–50 cm across and of similar depth. Humic acid seeping down the sides of the boulders has, over thousands of years, dissolved deep, near-vertical flutes out of the hard basalt. In some places the fluting is no longer vertical as the boulders have rolled over or tilted since it was formed. Basalt karst occurs in a number of places in northern New Zealand with some of the best examples at Wairere Boulders, but also at Stoney Batter, Waiheke Island; Ti Pt, Leigh; Lake Manuwai, Kerikeri; and Stoney Knowe, Helena Bay. Excellent examples of karst features developed on basalt boulders can be seen on Norfolk Island, Tasman Sea.

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Wikipedia