Cook Strait
Cook Strait lies between the North and South Islands of New Zealand. To the west is the Tasman Sea and to the east the Pacific Ocean. On the south side lies Cloudy Bay and the islands and entrances to the Marlborough Sounds. On the north side lies a coast which runs 40 kilometres from Turakirae Head to Cape Palliser, then crosses the entrance to Wellington harbour and moves along some Wellington suburbs before continuing another 15 kilometres along the Makara Coast to Makara Village.
In good weather one can see clearly across Cook Strait. At its narrowest point 23 kilometres (14 miles) separate Cape Terawhiti in the North Island from Perano Head on Arapawa Island in the Marlborough Sounds.[1] Counter-intuitively, at this point the South Island's coast lies further north than that of the North Island.
The strait takes its name from Captain James Cook, the first European commander to sail through it, in January - February 1770. In Māori it has the name Raukawa or Raukawa Moana. Raukawa may mean "bitter leaves". [2]
Geology
The shores of Cook Strait on both sides are mostly composed of steep cliffs. The beaches of Cloudy Bay, Clifford Bay, and Palliser Bay shoal gently down to 70 fathoms, where there is a more or less extensive submarine plateau. However the bottom topography of the strait is complex. To the east is the Cook Strait Canyon with steep walls descending eastwards into the bathyal depths of the Hikurangi Trench. To the north-west of the Cook Strait Canyon lies the Narrows Basin, where depths of water between 150 and 200 fathoms predominate. Fisherman's Rock in the north end of the Narrows Basin near the centre rises to within a few feet of low tide, and is marked by wave break in rough weather. Leading into the Narrows Basin from the north-west is the North West Trough, a rather shallow submarine “valley” lying across the northern end of the Marlborough Sounds. Its head lies near the centre line of Tasman Bay.
Near shore on both coasts from the Narrows both to north and west, the bottom topography is most irregular, particularly around the coast of the South Island where the presence of offshore islands, submerged rocks, and the entrances to the sounds, create violent eddy conditions.[1]
The strait has an average depth of 128 metres (420 feet).
European history
When Dutch explorer Abel Tasman first saw New Zealand in 1642, he interpreted the area of Cook Strait as a bight closed to the east. He named it Zeehaen's Bight, after the Zeehaen, one of the two ships in his expedition. In 1769 James Cook found that the strait formed a navigable waterway.
Cook Strait attracted European settlers in the early 19th century. Because of its use as a whale migration route, whalers established bases in the Marlborough Sounds and in the Kapiti area. From 1840 more permanent settlements sprang up, first at Wellington, then at Nelson and at Wanganui (Petre). At this period the settlers saw Cook Strait in a broader sense than today's ferry-oriented New Zealanders: for them the strait stretched from Taranaki to Cape Campbell, so these early towns all clustered around "Cook Strait" (or "Cook's Strait", in the pre-Geographic Board parlance of the times) as the central feature and central waterway of the new colony.
Shipping traffic through the Strait has been significant since the early days of colonisation, and a number of shipwrecks have taken place, notably that of the Wahine in 1968.
Cables
Communications and electric-power cables, linking the North and South Islands, follow the strait’s floor.[3]
Tidal flow
The tidal flow through Cook Strait is particularly interesting, as on each side of the strait the tide is almost exactly out of phase so that high water on one side meets low water on the other. Strong currents result, with almost zero tidal height change in the centre of the strait. Yet, although the tidal surge should flow in one direction for six hours and then the reverse direction for six hours, a particular surge might last eight or ten hours with the reverse surge enfeebled. In especially boisterous weather conditions, the reverse surge might be entirely overcome so that the flow remains in the same direction through three surge periods and longer. A further complication for Cook Strait's pattern of current flow is that the tides at the north end have the ordinary two cycles of spring-neap tides in a month (as found along the west side of the country), but the south end's tidal pattern has only one cycle of spring-neap tides a month, as found on the east side of the country.
Power generation
In April 2008, a resource consent was granted to a small company for the installation of a $10m experimental underwater tidal stream turbine capable of producing one megawatt of power in eighty metres of water 4.5 kilometres due south of Sinclair Head. The company claims there is enough tidal movement in Cook Strait to generate 12GW of power, more than one-and-a-half times New Zealand's current requirements.[4]
Ferry services
Regular ferry services run between Picton in the Sounds and Wellington. The strait often experiences rough water and heavy swells from strong winds, especially from the south. New Zealand's position directly athwart the Roaring Forties means that the strait funnels westerly winds and deflects them into northerlies. Due to this the Cook Strait is regarded as one of the most dangerous and unpredictable Waters in the world.
Swimming the strait
Māori accounts tell of at least one swimmer who conquered the strait in 1831. Following the crossing by Barrie Devenport on 20 November 1962, many successful swims across the strait have taken place. Lynne Cox swam it in 1975, famously stopping often and diving to the sea floor to collect shellfish, crayfish and other bottom feeders for her husband. By 2008, 71 successful single crossing had been made by 61 individuals, and 3 double crossings had been made by 2 individuals. Crossing times are largely determined by the strong and sometimes unpredictable currents that operate in the strait.[5]
See also
Notes
- ^ a b McLintock, A H, Ed. (1966) Cook Strait from An Encyclopaedia of New Zealand, updated 18-Sep-2007
- ^ Reed, A W (2002) The Reed Dictionary of New Zealand Place Names, Reed, page 99.
- ^ A Powerful link: The Cook Strait Cable
- ^ Green light for Cook Strait energy generator trial NZ Herald. Apr 15, 2008
- ^ Cook Strait Swim
External links
- Encyclopaedia of New Zealand link
- Cook Strait: Ship Wrecks, Swells and Gales
- New Zealand's Cook Strait Rail Ferries:
41°13′46″S 174°28′59″E / 41.22944°S 174.48306°E
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