At the northern end of Takapuna Beach curious-looking basalt formations can be seen across the shore platform at low tide.
Ever wondered what they are?
These formations are the fossilised remnants of an ancient forest?
The cylindrical moulds were formed approximately 200,000 years ago during the eruption of nearby Lake Pupuke volcano, when the sea level was much lower than it is today. Lava flows engulfed the forest and encased their lower trunks. The trees themselves were incinerated by the hot lava but the shape of their trunks and fallen branches were preserved as the lava cooled and solidified around them.
The size and symmetry of some of the moulds that have been preserved suggest that some of the trees are likely to have been kauri. The most impressive of these is a 1.6-metre diameter, 3-meter-deep tree cast, located beneath a protective grating about 100m north along the coastal walkway from Takapuna Beach. A 1.2-metre-wide imprint of a fallen trunk, believed to have belonged to a kauri, can also be seen preserved in the lava flow at Takapuna Beach.
In some locations, arches connecting the tree moulds can also be observed. These formed when the top of the lava flow cooled and formed a hard roof. Some thicker areas of the roof remained, creating the arches still seen today. Takapuna Reef Fossil Forest is one of the best examples in the world of a lava-preserved fossil forest and is scheduled for protection as an Outstanding Natural Feature in the Auckland Unitary Plan.