Hawke Bay is a large, rather regularly oval indentation on the east coast of the North Island, its northern end nearly at the thirty-ninth parallel of south latitude, its southern end at 39° 38'. Mahia Peninsula lies at its north-eastern end and Cape Kidnappers at the south. The 100-fathom line marking the edge of the continental shelf lies just within the line joining Mahia and Kidnappers, and the water of the bay gently and steadily shoals from this line to the shore. At a distance of 22 miles off shore from Napier, an area of submarine springs has been mapped and it is believed that these mark the outlet from the notable Heretaunga Artesian Basin in the vicinity of Napier and Hastings at the southern end of the Bay.
From Wairoa to Nuhaka in the north and from Tangoio to Te Awanga in the south are more or less extensive areas of prograded and alluviated coast, but the rest of the coastline, except for the tombolo isthmus of Mahia joining the former island, now Mahia Peninsula, to the mainland, is formed from vertical or nearly vertical cliffs in soft and rapidly eroding upper Cretaceous and Tertiary rocks. From Waihua River mouth, a little to the south of Wairoa, the rocks were all laid down in the Pleistocene which commenced about 3 million years ago. The spectacular coastal section from Te Awanga to Black Reef, which lies about half a mile to the west of Cape Kidnappers, exposes an impressive river delta which existed during the Lower Pleistocene. This has now been uplifted, tilted, and much eroded.
Although small coastal vessels at one time did enter the Wairoa River and a small, purely fishing wharf exists at Waikokopu at the western end of the isthmus of Mahia, the only port on the bay is the artificial Napier Harbour, which for a number of years has been third on the list for tonnage handled in New Zealand. Prior to the Napier earthquake of 1931, Napier Harbour lay within the restricted entrance of the Old Ahuriri Lagoon, but the uplift of 6 ft so markedly altered the conditions that plans for a breakwater harbour, which were even then under discussion, were immediately proceeded with. The inner harbour is now used only by yachts and launches. Until the earthquake of 1931, the Ahuriri Lagoon was an extensive arm of the bay lying behind gravel bars and stretching south-west from Napier to Greenmeadows, south to Awatoto, and north to Bayview. Early in the period of settlement, extensive reclamation had been undertaken in Napier both to the north and south of Scinde Island, and the great bulk of the flat land of Napier was at one time part of the old Ahuriri Lagoon reclamation.
Hawke Bay has an origin in the geological structure of the area; all rocks around it dip into the bay and in consequence it is the focus of the drainage of the district. No fewer than five large rivers flow to its shores, namely, from south to north, the Tukituki, draining the northern Central Ruahine Range; the Ngaruroro, draining the northern end of the Ruahine Range and the eastern slopes of the Kaimanawa Range; the Tutaekuri, draining the Black Birch and Kaweka Ranges; the Mohaka, draining the northern face of the Kaweka Range, the Ahimanawa Range, and the southern end of the Huiarau Range; and the Wairoa, which drains not only the Waikaremoana area but also as far north as Waerengaokuri, a few miles west of Gisborne. The steep cliffs on the western shore of Hawke Bay collapse from time to time in unusual and spectacular dry rockfalls. Although these rockfalls occur normally, there was an unusual number of them at the time of the Napier earthquake when the largest, a few miles south of the mouth of the Mohaka River, “flowed” almost half a mile into Hawke Bay. Even now its remains form a small point.
Prior to European times the shores of Hawke Bay supported a considerable Maori population. The first name mentioned in the legends of settlement of the shore of Hawke Bay was that of Whatonga, who settled at Mahia. The name Hawke Bay was given by Captain Cook after Sir Edward Hawke, First Lord of the Admiralty from 1766 to 1771.
by Thomas Ludovic Grant-Taylor, M.SC., New Zealand Geological Survey, Lower Hutt.