Mount Maunganui / Mauao

Mount Maunganui, aka Mauao (‘caught by the dawn’ in Māori), or simply the Mount, is a rhyolitic volcanic dome at the southern entrance to the Tauranga Harbour. Standing at 252m, Mount Maunganui is steeply sided with a flat top and is estimated to be around 2.3-3.5 million years old. Rhyolite domes are the most prominent landforms in the Tauranga area, of which Mount Maunganui is the most iconic.

Mount Maunganui is part of the Mount Maunganui Group, comprising four rhyolitic volcanic centres in the Tauranga area that range in age from about 2 to 3.5 million years. In addition to the Mount, the Mount Maunganui Group includes the two islands off Maunganui Beach (Motuotau and Moturiki) and Mount Drury. This collection of volcanoes has the same geological make up (geochemistry) and similar ages, which differentiates it from the other volcanic systems in the Tauranga region.

Overall, Mount Maunganui and its siblings are part of other domes and volcanic flows in the Tauranga area that make up the local Tauranga Volcanic Zone. In a wider context, the Tauranga Volcanic Zone is part of the Coromandel Volcanic Zone which stretches from Kaimai (south of Tauranga) to Great Barrier Island in the north.

Over the past few thousand years, sediments have built up to form the present Tauranga Harbour. It is known as a barrier-enclosed estuary due to the presence of Matakana Island, which acts as the barrier. Dunes that have accumulated over the last few thousand years have joined Mount Maunganui to the mainland.

- From the top, have a look at the two islands off Maunganui Beach and the Mount Drury Reserve: these are the Mount’s siblings, related by their similar geological make up and age.
- Notice how strong the rock is: volcanic domes are viscous (sticky) extrusions of lava from a volcano. The fact that this structure is still present and not completely eroded away even though it is 2 million years old is because of the original high silica and low gas content in the magma, meaning that it solidified to a dense rock very resistant to degradation.
- Notice also the light colouration of the rock: rhyolite is often pale coloured. Lava domes are often the product of highly silicious magma which is sticky and slow moving, and therefore unable to flow far from the vent.
- The stretch of land that joins the Mount was created by deposition of sediment once sea levels had risen to their present level in the Holocene (about 7000 years ago). This is known as a ‘tombolo’.
- The Mount is sacred to local iwi (Māori tribes) and the area shows evidence of human habitation such as pa (fortified village) sites.