The District’s dramatic skyline is dominated by the geological structures of Bream Head and offshore islands to the east, the result of the powerful forces that shaped the land throughout our earth’s history.
Much of the interior of Whangarei comprises gently rolling to moderately steep hill country, studded with scoria cones such as those found at Maungatapere and Maunu. To the south and west, dominant features include uplifted blocks charactised by steep hills and jagged ranges. No part of the District is more than 800 metres above sea level.
The Whangarei District is dotted with the conical reminders of long extinct volcanoes. Areas that were once lava flows now form gently rolling countryside of sought after volcanic soils. The volcanic peaks at Whangarei Heads are part of one large family of volcanoes. The Hen and Chicken islands and Sail Rock are a separate group from around the same period dating back 20 million years. The peaks at Hikurangi and Maungatapere were formed around 10,000 years ago.
Manaia and Bream Head have rocks that date back 135 million years giving credence to the science behind New Zealand being part of the great land mass, Gondwanaland.
Outstanding topographical features that form the boundaries and hills to the west and south of the District, including the Bryderwyn Range, the Tangihua Ranges and Taipuha, are remnants of great blocks of rock that have been lifted, lowered and twisted by tectonic plate movement. The basement blocks date back to the Jurassic Period.
As the last Ice Age melted, flooding the Hatea, Mangapai and Otaika river valleys, rising waters formed what is now Whangarei Harbour.
Residues of this geological history include coal fields at Hikurangi, Kamo and Kiripaka and, limestone deposits at Portland, Hikurangi and Waipu.
There are two natural lakes in Whangarei District, Lake Ora, north west of Whangarei City and a dune lake near the Ruakaka Racecourse. Lake Waro is an artificial lake north of the Hikurangi township.
The District has a dense network of rivers and streams although most are short with relatively small catchments. Rivers such as Hatea, Ngunguru and Mangapai flow into large harbours or estuaries.
Whangarei District has 270km of coastline characterised by irregular rocky headlands, sheltered harbours, sandy bay, estuaries and tidal mud flats.
DRY RIVER VALLEYS
Travelling to the coast, much of the dramatic landscape is defined by deep dry river valleys, running down to beaches and bays off the coastline.
Large islands of the District include the Poor Knights Islands, Taranga Island and Marotere Islands, commonly known as the Hen and Chicks, and Sail Rock. The Poor Knights Islands are the heavily eroded rims of a large volcano, which erupted some 10 million years ago. This volcano was possibly 1000 metres high, measuring 15 – 25 kilometres in diameter. The Hen and Chicks and Sail Rock are from a group of volcanoes dating back 20 million years.
None of these islands are inhabited and all are protected conservation areas.