The Hikurangi Trench is a linear deep in the Pacific Ocean

Pacific Ocean

The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

 off the east coast of the North Island

North Island

The North Island is one of the two main islands of New Zealand, separated from the much less populous South Island by Cook Strait. The island is in area, making it the world's 14th-largest island...

 of New Zealand

New Zealand

New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

, lying between the southern end of the Cook Strait

Cook Strait

Cook Strait is the strait between the North and South Islands of New Zealand. It connects the Tasman Sea on the west with the South Pacific Ocean on the east....

 and the Chatham Rise

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...

. Though much shallower, it is the southward continuation of the Kermadec Trench

Kermadec Trench

The Kermadec trench is one of Earth's deepest oceanic trenches, reaching a depth of . Formed by the subduction of the Pacific Plate under the Indo-Australian Plate, it runs over a thousand kilometres parallel with and to the east of the Kermadec Ridge and island arc, from near the northeastern tip...

 and forms part of the Kermadec-Tonga Subduction Zone

Kermadec-Tonga Subduction Zone

The Kermadec-Tonga Subduction Zone is a convergent plate boundary which stretches from the North Island of New Zealand northward, and includes the Hikurangi Trough, the Kermadec Trench and the Tonga Trench...

. It represents the part of the subduction

Subduction

In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge. These 3D regions of mantle downwellings are known as "Subduction Zones"...

 zone where the thick oceanic Hikurangi Plateau

Hikurangi Plateau

Hikurangi Plateau is an Early Cretaceous basaltic oceanic plateau in the southwestern Pacific Ocean. The portion of the plateau exposed on the seafloor has an area of 350,000 km2, and including the portions subducted beneath the...

 is subducting beneath continental crust

Continental crust

The continental crust is the layer of igneous, sedimentary, and metamorphic rocks which form the continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called sial due to more felsic, or granitic, bulk composition, which lies in...

 of the Indo-Australian Plate

Indo-Australian Plate

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

. By contrast, the Kermadec and Tonga Trench

Tonga Trench

The Tonga Trench is located in the South Pacific Ocean and is deep at its deepest point, known as the Horizon Deep.The Tonga Trench is a convergent plate boundary. The trench lies at the northern end of the Kermadec-Tonga Subduction Zone, an active subduction zone where the Pacific Plate is being...

es represent the parts of the subduction zone where oceanic crust

Oceanic crust

Oceanic crust is the part of Earth's lithosphere that surfaces in the ocean basins. Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium...

 of the Pacific Plate

Pacific Plate

The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres, it is the largest tectonic 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 3750 metres (12,303.1 ft).

At the southern end of the trench, off the coast of Marlborough, New Zealand

Marlborough, New Zealand

Marlborough is one of the regions of New Zealand, located in the northeast of the South Island. Marlborough is a unitary authority, both a region and a district, and its council is located at Blenheim. Marlborough is known for its dry climate, the picturesque Marlborough Sounds, and sauvignon blanc...

, 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 for which the town of Kaikoura

Kaikoura

Kaikoura is a town on the east coast of the South Island of New Zealand. It is located on State Highway 1 180 km north of Christchurch.Kaikoura became the first local authority to reach the Green Globe tourism certification standard....

 is famous.

The plate boundary continues inland along the Hope Fault

Hope Fault

The Hope Fault is an active dextral strike-slip fault in the northeastern part of South Island, New Zealand. It forms part of the Marlborough Fault System, which accommodates the transfer of displacement along the oblique convergent boundary between the Indo-Australian Plate and Pacific Plate,...

. Here the plates converge much more obliquely, exhibiting transpression

Transpression

Transpression is a geological term used to describe a region of the Earth's crust that experiences strike-slip shear and a component of shortening, resulting in oblique shear. Transpression typically occurs at a regional scale, such as plate boundaries that have an oblique convergence. More...

instead of subduction.