The Lord Howe Seamount Chain formed during the

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

. It features many

coral Corals are colonial marine invertebrates within the subphylum Anthozoa of the phylum Cnidaria. They typically form compact Colony (biology), colonies of many identical individual polyp (zoology), polyps. Coral species include the important Coral ...

-capped guyots and is one of the two parallel seamount chains alongside the east coast of

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

; the Lord Howe and Tasmantid seamount chains both run north-south through parts of the

Coral Sea The Coral Sea () is a marginal sea of the Pacific Ocean, South Pacific off the northeast coast of Australia, and classified as an Interim Biogeographic Regionalisation for Australia, interim Australian bioregion. The Coral Sea extends down t ...

and

Tasman Sea The Tasman Sea is a marginal sea of the South Pacific Ocean, situated between Australia and New Zealand. It measures about across and about from north to south. The sea was named after the Dutch explorer Abel Janszoon Tasman, who in 1642 wa ...

. These chains have

longitude Longitude (, ) is a geographic coordinate that specifies the east- west position of a point on the surface of the Earth, or another celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek lett ...

s of approximately 159°E and 156°E respectively.

Geography

The Lord Howe Seamount Chain has been known under a variety of different gazetted names, including the Lord Howe Seamounts, Lord Howe Guyots, Lord Howe Rise Guyots and the Middleton Chain. The Lord Howe Seamount Chain is on the western slope of Lord Howe Rise, a deep-sea elevated plateau which is a submerged part of

Zealandia Zealandia (pronounced ), also known as (Māori language, Māori) or Tasmantis (from Tasman Sea), is an almost entirely submerged continent, submerged mass of continental crust in Oceania that subsided after breaking away from Gondwana 83� ...

. The Tasmantid and Lord Howe seamount chains are both broadly within the Tasman basin which is the

abyssal plain An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between . Lying generally between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth's surface. They ...

between Lord Howe Rise and the Australian

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an islan ...

. The two chains lie on opposite sides of the Dampier Ridge which is believed to be a submerged continental fragment, that is over 250 million years old, and had split from the Australian plate during Tasman Sea formation. Earlier magnetic studies suggest that the Dampier Ridge is adjunct to the Tasman Sea's former extinct mid oceanic ridge, and it had been postulated to be much younger. The Lord Howe Seamount Chain extends from north of the Chesterfield group of islands (17°S) to Flinders Seamount (34.7°S).Przeslawski et al.
Biogeography of the Lord Howe Rise region, Tasman Sea
'. Deep-Sea Research Part II 58 (2011) 959–969. It includes the officially named Nova Bank, Argo and Kelso seamounts, Capel and Gifford guyots, Middleton and Elizabeth reefs,

Lord Howe Island Lord Howe Island (; formerly Lord Howe's Island) is an irregularly crescent-shaped volcanic remnant in the Tasman Sea between Australia and New Zealand, part of the Australian state of New South Wales. It lies directly east of mainland Port ...

and

Ball's Pyramid Ball's Pyramid is an uninhabited islet in the Pacific Ocean located southeast of Lord Howe Island, between Australia and New Zealand. The steep rocky basalt outcrop is the eroded plug of a shield volcano and caldera that formed 6.4million ye ...

Geology

The Lord Howe and Tasmantid chains each resulted from the Indo-Australian Plate moving northward over a stationary hotspot; historically the hotspot for the Lord Howe chain was expected to presently be beneath Flinders Seamount.W. J. Morgan and J. P. Morgan.
Plate velocities in hotspot reference frame: electronic supplement
' but is now thought likely to be somewhat to the south of this, possibly beyond the Heemskerck and Zeehaen seamounts. Indeed the dating of this chain has only been as far south as

which erupted 6.5 million years ago and there are other gaps in relevant knowledge of this hotspot chain. The chain has now been characterised by compositional analysis to be related at 28 million years to the South Rennell Trough spreading center as its potential initiation point with lessening

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

being erupted progressively as the younger seamounts of the hot spot were formed. On the Australian mainland, a third north-south sequence of extinct volcanoes (which includes the Glass House Mountains) is likely to have the same origin. The Lord Howe Seamount Chain includes the following features:

References

{{reflist Seamount chains Guyots Hotspot tracks Volcanoes of Zealandia Seamounts of the Pacific Ocean Seamounts of the Tasman Sea

Geography

Geology

See also

References