The Kermadec Trench is a linear

ocean 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 south

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 continen ...

. It stretches about from the

Louisville Seamount Chain The Louisville Ridge, also known as the Louisville Seamount Chain, is an underwater chain of over 70 seamounts located in the Southwest portion of the Pacific Ocean. As one of the longest seamount chains on Earth it stretches some Vanderkluysen, ...

in the north (26°S) to the

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 ...

in the south (37°S), north-east of

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

North Island The North Island, also officially named Te Ika-a-Māui, is one of the two main islands of New Zealand, separated from the larger but much less populous South Island by the Cook Strait. The island's area is , making it the world's 14th-largest ...

. Together with the Tonga Trench to the north, it forms the -long, near-linear Kermadec-Tonga subduction system, which began to evolve in the Eocene when the Pacific Plate started to subduct beneath the Australian Plate. Convergence rates along this subduction system are among the fastest on Earth, /yr in the north and /yr in the south.

Geology

The Kermadec Trench is one of Earth's deepest oceanic trenches, reaching a depth of . Formed by the subduction of the

Pacific Plate The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate. The plate first came into existence 190 million years ago, at the triple junction between the Farallon, Phoenix, and Iza ...

under 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 ...

, it runs parallel with and to the east of the

Kermadec Ridge The Tonga-Kermadec Ridge is an oceanic ridge in the south-west Pacific Ocean underlying the Tonga- Kermadec island arc. It is the most linear, fastest converging, and most seismically active subduction boundary on Earth, and consequently has the ...

and

island arc Island arcs are long chains of active volcanoes with intense seismic activity found along convergent tectonic plate boundaries. Most island arcs originate on oceanic crust and have resulted from the descent of the lithosphere into the mantle alon ...

. The Tonga Trench marks the continuation of subduction to the north. The Kermadec Trench has a southern continuation in the

turbidite A turbidite is the geologic deposit of a turbidity current, which is a type of amalgamation of fluidal and sediment gravity flow responsible for distributing vast amounts of clastic sediment into the deep ocean. Sequencing Turbidites were ...

-filled Hikurangi Trough, but a series of seamounts on the Australian Plate act as a dam and prevents this turbidity from reaching the sediment-starved Kermadec Trench. Debris from a larger subducted seamount probably dammed the trench from 2 Ma to 0.5 Ma and similar events probably redirected sediments in similar ways before that. Two oceanic plates meet at the Kermadec Trench which is located far from any larger landmass. Because of this, the Pacific Plate as well as the trench itself is only covered by of sediments. The trench is almost perfectly straight and its simple geometry is the result of the uniformity of the subducting sea-floor. This sea-floor formed at the extinct Osbourn

Trough Trough may refer to: In science * Trough (geology), a long depression less steep than a trench * Trough (meteorology), an elongated region of low atmospheric pressure * Trough (physics), the lowest point on a wave * Trough level (medicine), the l ...

, located just north of the Louisville Seamount Chain. Abyssal hills on the subducting sea-floor are oriented perpendicular to the old spreading centre and the sea-floor is 72–80 Ma near the Louisville seamounts at the northern end and more than 100 Ma near Hikurangi Plateau at the southern end. There are no seamounts on the sea-floor near the Kermadec Trench except one sitting on the trench slope at which has been dated to 54.8±1.9 Ma. The Hikurangi Plateau formed part of the Ontong-Java-

Manihiki 250px, Map of Manihiki Atoll Manihiki is an atoll in the northern group of the Cook Islands known informally as the "Island of Pearls". It is located in the Northern Cook Island chain, approximately north of the capital island of Rarotonga, ma ...

Hikurangi Hikurangi is a settlement in Northland, New Zealand. The city of Whangārei is 17 km (11 miles) to the south, and Kawakawa is 39 km (24 miles) northwest. The Glenbervie Forest is southeast of the settlement. State Highway ...

large igneous province A large igneous province (LIP) is an extremely large accumulation of igneous rocks, including intrusive (sills, dikes) and extrusive (lava flows, tephra deposits), arising when magma travels through the crust towards the surface. The formation ...

(LIP) during the Ontong Java Event 120 . The Manihiki Plateau is currently subducting under the southern part of the Kermadec Arc but most of it has already been subducted. The LIP-arc collision occurred north of its present location, but oblique plate convergence has migrated the subducted plateau southward.

Fauna

In 2012, deep sea researchers discovered individuals of a species of giant amphipod at the trench's lowest depths. Unlike most

amphipod Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far descr ...

s, which are approximately 2.5 cm (1 inch) long, this species reaches up to 34 cm (13 inches) in length, and are milky-white. The second-deepest fish, the

hadal The hadal zone, also known as the hadopelagic zone, is the deepest region of the ocean, lying within oceanic trenches. The hadal zone ranges from around below sea level, and exists in long, narrow, topographic V-shaped depressions. The cumula ...

snailfish '' Notoliparis kermadecensis'', is endemic to the trench and occupies a very limited depth range, . A species of

pearlfish Pearlfish are marine fish in the ray-finned fish family Carapidae. Pearlfishes inhabit the tropical waters of the Atlantic, Indian, and Pacific Oceans at depths to , along oceanic shelves and slopes. They are slender, elongated fish with no ...

, '' Echiodon neotes'', has been caught in the Kermadec Trench at a depth of . All other known pearlfishes live in the range and the presence of ''E. neotes'' at this depth remains unexplained.

''Nereus'' research submarine

In May 2014, the ''Nereus'', an unmanned research submarine operated by the

Woods Hole Oceanographic Institution The Woods Hole Oceanographic Institution (WHOI, acronym pronounced ) is a private, nonprofit research and higher education facility dedicated to the study of marine science and engineering. Established in 1930 in Woods Hole, Massachusetts, it i ...

(WHOI), imploded due to high pressure at a depth of 9,990 metres while exploring the Kermadec Trench.

References

Notes Bibliography * * * * * *

External links

* An animation of a 3D model of the Kermadec Trench {{Coord, 28, S, 175, W, type:waterbody_source:dewiki, display=title Zealandia Geography of the Kermadec Islands Geography of the New Zealand seabed Oceanic trenches of the Pacific Ocean Subduction zones

Geology

Fauna

''Nereus'' research submarine

See also

References

External links