Auckland sits atop the Auckland Volcanic Field, a unique geological area dotted with 53 volcanoes. Many past eruptions produced significant lava flows, and within these flows, remarkable natural formations known as lava caves, or lava tubes, developed. These caves formed when the outer surface of a lava flow cooled and solidified, creating an insulating crust. Underneath this crust, molten lava continued to flow like a river. When the eruption ceased or the lava diverted, the molten interior drained away, leaving behind the hollow, cave-like tube. This process has gifted the Auckland region a hidden network of subterranean passages beneath its urban landscape.
There are around 200 distinct cave systems. However, the many of these have been lost over the last century and a half. Extensive quarrying for scoria, widespread urban development, road construction, and landfilling have led to the destruction or filling-in of many cave systems. While it’s hard to give an exact figure, it’s thought that perhaps only around 50 or so significant cave systems remain known or partially intact today, though many of these are fragmented, blocked, or inaccessible.
Auckland boasts several well-known caves, including Stewart’s Cave in Three Kings. This impressive cave stretches 180 metres in length and reaches heights of up to 8 metres in certain sections, making it one of the city’s largest. Another notable example is the Wiri Lava Tube at Matukutūruru / Wiri Mountain. As Auckland’s longest single lava tube, it extends for 290 metres and showcases remarkable flow ledges.