Manukau Cave a Scientific Reserve

Forest and Bird, Issue 291, 1 February 1999, Page 13

Manukau Cave a Scientific Reserve

fter nearly three decades of campaigning by conervationists, a volcanic lava cave within New Zealand’s largest city, Manukau, has become a scientific reserve. The Minister of Conservation, Dr Nick Smith, descended into the depths of the 280-metre cave to sign the reserve document. The Matukururu Scientific Reserve protects a lava tunnel, formed as molten lava spilled from Wiri Mountain, one of Auckland’s 48 basalt volcanoes. As the lava set on the outside, the molten centre continued to flow, leaving the tunnel behind it. Part of the cave has a "Gothicshaped’ cross-section, with some small lava stalactites hanging from its ceiling. The floor is marked with parallel ridges left by the escaping lava. The values, however, are all underground and a permit is required for access through

what is still a working quarry. The cave is the most spectacular of the few lava caves left on the Auckland volcanic field. Auckland’s volcanoes are geologically young, erupting in succession at intervals from about 150,000 years ago till some 600 years ago when Rangitoto emerged from the Waitemata Harbour. The Wiri field is estimated to be 28,000 years old. Most of the volcanoes on the Auckland isthmus have been damaged and many have vanished completely, excavated away for such uses as road and rail foundations. Quarrying over 30 years by the old New Zealand Railways and subsequent Crown leasees has taken away the bulk of Wiri mountain. A case before the Planning Tribunal, brought by the Historic Places Trust and the Geological Society, saw the cave protected under the Manukau District Scheme in 1970. Yet

quarrying continued while people argued for further protection. Eventually, excavation stopped only metres short of destroying the formation. The name Matukururu, means the ‘watchful bittern’ the Maori name for McLaughlin’s Mountain which was once paired with Matukutureia, the ‘careless bittern’ which was Wiri mountain on the same volcanic field.