North Head / Maungauika

North head is a very popular location due to its stunning views, accessible walkways and fascinating military fortifications. It is also a great place to have a close-up look at the volcanic rocks created during violent eruptions when magma interacts with water. The rapid expansion of steam and volcanic gases blows the magma into very small pieces which are blasted up and sideways to form layers of tuff. Each layer represents an explosion and they might typically occur minutes apart. The upper part of North Head is made of mainly of red scoria, which is exposed in a few places, and was the product of fire-fountaining eruptions occurring once the water was no longer able to reach the hot magma.There is also a lava flow that was produced in the last phase of the eruption, but it is mostly hidden to the west of the cone.

The abundant fortifications dug into North Head are fascinating to explore. If you enter the tunnels, and have a torch, take a close look at the places where the rocks are exposed. It's not often that you can get right inside a volcano! The same tuff beds can be seen in the sea cliffs that you can access down one of several pathways. They show interesting features including interspersed scoria layers, collapse structures (faults and tilted bedding), lava bombs, and fragments of the local country rocks through which the eruption occurred (such as pieces of whitish coloured sandstone). The scoria at the top of the cone is best seen in the face of an old quarry on the access road below the car park.