Paku Hill, the volcanic guardian of Tairua

Paku (originally Paaku, meaning 'winged') Hill represents the remnants of the last phase of activity at a large rhyolite volcano that formed about 7-8 million years ago. The earlier more explosive phase of the eruption led to the emplacement of widespread ignimbrites (thick pyroclastic flow deposits). This was followed by the eruption of viscous (sticky) silica-rich lava in the vent, which formed a rhyolite dome at the surface (the current outer slopes of Paku). A later extrusion pushed more lava up, now represented by the two peaks of Paku. Most of the older, softer ignimbrites have long since eroded away, leaving only remnants of the last phases of the eruption preserved. There are great views of Tairua Harbour from the summit. Interestingly, the harbour was once a broad river valley (when sea level was much lower than it is today). As sea levels rose following the Last Glaciation, the river valley was drowned and filled with sand, to form the Tairua Estuary as we know it today. This influx of sand also formed the Tombolo (narrow neck of dune sand) that joins Paku, which until then was an island, to the mainland.

The rhyolite lava can be viewed at the base of Paku at the end of Ocean Beach. Have a look out for the interesting layers and swirls in the lava. This is a result of 'flow banding', a type of layering that develops in flowing lava as crystals segregate due to friction. The outcrops also display other interesting patterns and structures that have formed due to a combination of jointing, iron-oxide staining, weathering and erosion from wave action. There are also a few small outcrops of weathered rhyolite lava near the summit.

At the summit enjoy a spectacular view of Tairua Harbour, and imagine what the valley might have looked like when sea levels were around 120 m lower than present.