The Hikurangi Trench, also called the Hikurangi Trough, is an

oceanic trench Oceanic trenches are prominent long, narrow topographic depressions of the ocean floor. They are typically wide and below the level of the surrounding oceanic floor, but can be thousands of kilometers in length. There are about of oceanic tren ...

in the bed of the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contin ...

off the east coast of the North Island of New Zealand, lying between the southern end of the

Cook Strait Cook Strait ( mi, Te Moana-o-Raukawa) separates the North and South Islands of New Zealand. The strait connects the Tasman Sea on the northwest with the South Pacific Ocean on the southeast. It is wide at its narrowest point,McLintock, A ...

and the

Chatham Rise The Chatham Rise is an area of ocean floor to the east of New Zealand, forming part of the Zealandia continent. It stretches for some from near the South Island in the west, to the Chatham Islands in the east. It is New Zealand's most productiv ...

. It is the southward continuation of the much deeper

Kermadec Trench The Kermadec Trench is a linear ocean trench in the south Pacific Ocean. It stretches about from the Louisville Seamount Chain in the north (26°S) to the Hikurangi Plateau in the south (37°S), north-east of New Zealand's North Island. Toget ...

. It lies in the Hikurangi Margin subduction zone, which is the southern extension of the

Kermadec-Tonga subduction zone The Kermadec-Tonga subduction zone is a convergent plate boundary that stretches from the North Island of New Zealand northward. The formation of the Kermadec and Tonga Plates started about 4–5 million years ago. Today, the eastern boundary ...

. The Hikurangi Margin is the subduction zone where the thick oceanic

Hikurangi Plateau The Hikurangi Plateau is an oceanic plateau in the South Pacific Ocean east of the North Island of New Zealand. It is part of a large igneous province (LIP) together with Manihiki and Ontong Java, now located and north of Hikurangi respective ...

is subducting beneath

continental crust Continental crust is the layer of igneous, sedimentary, and metamorphic rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called '' sial'' be ...

of the

Indo-Australian Plate The Indo-Australian Plate is a major tectonic plate that includes the continent of Australia and the surrounding ocean and extends northwest to include the Indian subcontinent and the adjacent waters. It was formed by the fusion of the Indian an ...

. By contrast, the Kermadec and Tonga trenches represent the parts of the subduction zone where

oceanic crust Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic ...

of the Pacific Plate is subducting beneath oceanic crust of the Indo-Australian Plate. Although shallower than the trenches north of it, the Hikurangi Trench reaches depths of 3,000 metres as close as 80 kilometres from shore. Its maximum depth is about .Keith B. Lewis, Jean-Yves Collott and Serge E. Lallemand (1998)
The dammed Hikurangi Trough: a channel-fed trench blocked by subducting seamounts and their wake avalanches (New Zealand-France GeodyNZ Project)
''Basin Research'' 10, 441-468. At the southern end of the trench, off the coast of the

Marlborough region Marlborough District or the Marlborough Region (, or ''Tauihu''), commonly known simply as Marlborough, is one of the 16 regions of New Zealand, located on the northeast of the South Island. Marlborough is a unitary authority, both a distric ...

, the seabed rises sharply, and because of the prevailing winds and tides in this area, many deep water species are found close to the shore. This food source attracts the

whales Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. As an informal and colloquial grouping, they correspond to large members of the infraorder Cetacea, i.e. all cetaceans apart from dolphins and ...

for which the town of Kaikoura is famous. The plate boundary continues inland along the

Marlborough Fault System The Marlborough Fault System is a set of four large dextral strike-slip faults and other related structures in the northern part of South Island, New Zealand, which transfer displacement between the mainly transform plate boundary of the Alpine ...

, linking through to the

Alpine Fault The Alpine Fault is a geological fault that runs almost the entire length of New Zealand's South Island (c. 480 km) and forms the boundary between the Pacific Plate and the Indo-Australian Plate. The Southern Alps have been uplifted on the f ...

. Here the plates converge much more obliquely, exhibiting

transpression In geology, transpression is a type of strike-slip deformation that deviates from simple shear because of a simultaneous component of shortening perpendicular to the fault plane. This movement ends up resulting in oblique shear. It is generally v ...

instead of subduction.

References

* Zealandia Geography of the New Zealand seabed Oceanic trenches of the Pacific Ocean Subduction zones {{marine-geo-stub

See also

References