What remains of Wiri Mountain hints at a fascinating past. This area was once a vast sprawling maunga. It covered around 18 hectares. At its summit, Wiri Mountain stood about 90 meters high. Quarrying has leveled almost all of it.
Wiri Mountain was also an impressive Māori pā. This village settlement dates back to the thirteenth century AD. Around the slopes, inhabitants created short terraces. They cut into the slopes or built scoria rock retaining walls. These terraces served many purposes. They were used for living, food storage, and gardening.
On the lower slopes, earth-and-stone walls radiated outwards. They extended into the surrounding lava fields. These divided spaces were used for growing crops. Like many maunga, large-scale gardens likely expanded. They reached into the fertile volcanic soils surrounding Wiri Mountain.
Geologically, Wiri Mountain owes its existence to a series of volcanic eruptions. The last eruption was an explosive fire-fountaining event. It created a large scoria cone with a crater at its summit. Lava erupted through fissures around the cone’s lower flanks. It flowed outwards in all directions. The lava completely encircled the cone. It extended 1 kilometer to the north and 1.5 kilometers to the south. Scientists accurately dated a tree caught in the northern lava flow. They determined this eruption occurred around 32000 years ago. Many of Auckland’s volcanoes erupted around that time.
Beneath the northern part of Wiri Mountain lies a hidden wonder. The Wiri Lava Cave was created by lava carving through the landscape. The outer edges cooled leaving behind a cavity. Positioned only 4 meters below Wiri Station Road, it’s quite expansive. It measures over 7 meters wide and 3 meters tall. The cave runs for approximately 300 meters. This lava cave is the best of its kind in New Zealand. It is protected as a Scientific Reserve. The cave is not open to the public.
Extensive quarrying significantly altered Wiri Mountain. It provided scoria for railway building. It also provided roading metal. A lake formed in the quarry pit. It sat at the center of the area previously occupied by the mountain. This lake has been drained and filled. There is no longer evidence of a hill at Wiri Mountain. The previous site is now used for various industrial activities. However, 3.8 hectares have been designated an Historic Reserve. This ‘U’ shaped plot fronts Wiri Station Rd. It is covered in piles of rubble, rocks, and overgrown weed vegetation.
In Māori mythology, Auckland’s isthmus sustained volcanic wounds. This happened in a battle between the Turehu people and Hunua Ranges. The Waitakere tohunga invoked the volcano deity Mataoho to intervene. Mataoho threw the whole isthmus into volcanic activity. The Hunua warriors were quickly routed by explosions and lava.
There are only 8 trees remaining on Wiri Mountain. The remaining vegetation is scrub, gorse, and wilding wattles. The 8 trees comprise 3 medium size Pine trees, 2 native trees and 3 exotic trees. All of these trees are in the area around Jacaranda House.
The Tūpuna Maunga Authority gained control of a small area. It is on the northern lower slopes. This was part of the Ngā Mana Whenua o Tāmaki Makaurau Collective Redress Act.
Despite the significant alterations Wiri Mountain has endured, it remains a place of historical and geological significance. The Wiri Lava Cave holds international renown. It features rare lava stalactites. The story of Wiri Mountain is a reminder of the dynamic forces that have shaped Auckland’s landscape. It also highlights the rich cultural heritage associated with its volcanic origins.