Hauraki Gulf

The Hauraki Gulf (Māori: Tīkapa Moana) is a coastal feature of the North Island of New Zealand. It has an area of 4000 km², and lies between, in anticlockwise order, the Auckland Region, the Hauraki Plains, the Coromandel Peninsula, and Great Barrier Island. Most of the gulf is part of the Hauraki Gulf Marine Park.

Hauraki is Māori for north wind. In 2014, the gulf was officially named Hauraki Gulf / Tīkapa Moana. The New Zealand Ministry for Culture and Heritage gives a translation of "the mournful sea" for Tīkapa Moana. In traditional legend, the Hauraki Gulf is protected by a taniwha named Ureia, who takes the form of a whale.

The gulf is part of the Pacific Ocean, which it joins to the north and east. It is largely protected from the Pacific by Great Barrier Island and Little Barrier Island to the north, and by the 80-kilometre-long Coromandel Peninsula to the east. It is thus well protected against all but northern winds.

Three large channels join the gulf to the Pacific. Colville Channel lies between the Coromandel Peninsula and Great Barrier, Cradock Channel lies between the two islands, and Jellicoe Channel lies between Little Barrier and the Northland Peninsula. To the north of Auckland several peninsulas jut into the gulf, notably the Whangaparāoa Peninsula. Tiritiri Matangi Island is near the end of this peninsula. Further north, Kawau Island nestles under the Tāwharanui Peninsula.

Numerous beaches dot the shores of the gulf, many of them well known for swimming and surfing.

During the last glaciation period the gulf was dry land, with the sea level being around 100–110 m (300 ft) lower than at present. The gulf was submerged when the sea reached its current level around 7200 years ago. During this period, the area was home to two river systems. The first of these was a river formed by two tributaries, the Mahurangi River and Waitematā Harbour (then a river). This river flowed north-east between modern day Little Barrier Island and Great Barrier Island, and emptied into the Pacific Ocean north of Great Barrier Island. The second was a stream formed by the major Hauraki Plains rivers: the Waihou River, Piako River and Waitakaruru River. Prior to the Ōruanui eruption 27,000 years ago, the Waikato River also flowed into the Hauraki Gulf at the Firth of Thames. The Hauraki Plains rivers were met by two tributaries, the Wairoa River to the west from modern-day Clevedon and the Umangawha Stream to the east, at Colville, Coromandel Peninsula. This river flowed north, along the plains, turning east and exiting towards the Pacific Ocean along the modern-day Colville Channel between the Coromandel Peninsula and Great Barrier Island.

In the west of the gulf lie a string of islands guarding the mouth of the Waitematā Harbour, one of Auckland's two harbours. These include Ponui Island, Waiheke Island, Tiritiri Matangi and the iconic dome of Rangitoto Island (a dormant volcano), which is connected to the much older Motutapu Island by a causeway. The islands are separated from the mainland by the Tāmaki Strait and Rangitoto Channel.

Other islands in the gulf include Browns Island, Motuihe Island, Pakihi Island, Pakatoa Island, Rākino Island, and Rotoroa Island in the inner gulf, around Waiheke and Rangitoto; Tarahiki Island just east of Waiheke; Motukawao Islands and Whanganui Island in the lee of the Coromandel Peninsula; and Channel Island in the outer gulf.