Lord Howe Rise | |
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Stratigraphic range: | |
Location | |
Coordinates | 28°S161°E / 28°S 161°E |
Region | South Pacific, Coral Sea, Tasman Sea |
Type section | |
Named for | Lord Howe Island |
The Lord Howe Rise is a deep sea plateau which extends from south west of New Caledonia to the Challenger Plateau, west of New Zealand in the south west of the Pacific Ocean. To its west is the Tasman Basin and to the east is the New Caledonia Basin. [1] Lord Howe Rise has a total area of about 1,500,000 km2 (580,000 sq mi), [1] and generally lies about 750 to 1,200 metres under water. [2] It is part of Zealandia, a much larger continent that is now mostly submerged, and so is composed of continental crust. Some have included the 3,500 m (11,500 ft) deep New Caledonia Basin as within the rise, given its continental crust origin, and this would give a larger total area of 1,950,000 km2 (750,000 sq mi). [3]
The Lord Howe Rise is associated with seafloor spreading which also resulted in the creation of the Tasman Sea. [4] The geology has not yet been characterised as well as other parts of Zealandia but when previous samples are analysed with current geological techniques they fit with the Zealandia hypothesis. [5] The seafloor is known to be dominated by soft sediments and the highest quality recent survey only mapped approximately 25,500 km2 (9,800 sq mi) of the western flank of the rise which is less than 1% of the total area of the rise. [3] In this area about 0.1% of the rises seafloor was classed as hard substrata based on a combined area of 31 km2 (12 sq mi) for 16 volcanic peaks. [3] Sandstone rocks dredged from the central Lord Howe Rise contained granite pebbles that were in the range 216–183 million years old. [6] It was rifted away from Eastern Australia in association with a mid-ocean ridge that was active from 80 to 60 million years ago, and now lies 800 kilometres offshore from mainland Australia.
The Lord Howe Rise contains a line of seamounts called the Lord Howe Seamount Chain which formed during the Miocene period when this part of Zealandia existed over the Lord Howe hotspot. One rhyolite sample has been dated at 97 million years drilled on the southern Lord Howe Rise. [6] Lord Howe Island was the last volcano to erupt on the rise 6.5 million years ago. [4]
Lord Howe Island and Ball's Pyramid cap a seamount towards the central east of the rise in an area known as the Lord Howe platform. The Lord Howe Seamount Chain extends northwards along the rise. The seamounts provide habitat to a diverse range of marine species which attracts commercial fishers, but cover a very small area, less than 1% of the total area of Lord Howe Rise. [7]
Further north is the Elizabeth and Middleton part of the Coral Sea Islands, which together with reefs around Lord Howe Island are the most southern coral reefs on Earth. [8]
The seabed on the rise is mostly sandy mud with some volcanic outcrops, gravel and boulders. [2]
The doubleheader fish, Coris bulbifrons , is endemic to reefs on the Lord Howe Rise and the West Norfolk Rise. [9]
Much of the basin remains unexplored in relation to oil and gas reserves. [10]
The Tasman Sea is a marginal sea of the South Pacific Ocean, situated between Australia and New Zealand. It measures about 2,000 km (1,200 mi) across and about 2,800 km (1,700 mi) from north to south. The sea was named after the Dutch explorer Abel Janszoon Tasman, who in 1642 was the first known person to cross it. British explorer Lieutenant James Cook later extensively navigated the Tasman Sea in the 1770s during his three voyages of exploration.
In marine geology, a guyot, also called a tablemount, is an isolated underwater volcanic mountain (seamount) with a flat top more than 200 m (660 ft) below the surface of the sea. The diameters of these flat summits can exceed 10 km (6.2 mi). Guyots are most commonly found in the Pacific Ocean, but they have been identified in all the oceans except the Arctic Ocean. They are analogous to tables on land.
A seamount is a large submarine landform that rises from the ocean floor without reaching the water surface, and thus is not an island, islet, or cliff-rock. Seamounts are typically formed from extinct volcanoes that rise abruptly and are usually found rising from the seafloor to 1,000–4,000 m (3,300–13,100 ft) in height. They are defined by oceanographers as independent features that rise to at least 1,000 m (3,281 ft) above the seafloor, characteristically of conical form. The peaks are often found hundreds to thousands of meters below the surface, and are therefore considered to be within the deep sea. During their evolution over geologic time, the largest seamounts may reach the sea surface where wave action erodes the summit to form a flat surface. After they have subsided and sunk below the sea surface such flat-top seamounts are called "guyots" or "tablemounts".
The South Tasman Rise is an area of seafloor that lies 550 km south of Hobart, Tasmania in the Southern Ocean where water depths are about 1,500 metres. The South Tasman Rise is also known as the Tasmania Ridge or South Tasmania Ridge. The South Tasman Rise is a sunken landbridge that used to connect Tasmania to Antarctica.
The Campbell Plateau is a large oceanic plateau south of New Zealand and the Chatham Rise. It originated in the Gondwanan breakup and is part of Zealandia, a largely submerged continent. The above sea level parts of the plateau — the Bounty Islands, Antipodes Islands, Auckland Islands and Campbell Island — form part of the New Zealand Subantarctic Islands which were declared a World Heritage Site in 1998. Large parts of the Campbell Plateau lie less than 1000 m below sea level. It rises to 500 m at the Pukaki Rise and emerges above sea level at the Auckland and Campbell Islands.
The Lord Howe Seamount Chain formed during the Miocene. It features many coral-capped guyots and is one of the two parallel seamount chains alongside the east coast of Australia; the Lord Howe and Tasmantid seamount chains both run north-south through parts of the Coral Sea and Tasman Sea. These chains have longitudes of approximately 159°E and 156°E respectively.
Lansdowne Bank, sometimes called Landsdowne Bank, is an extensive submerged bank located between the main island of New Caledonia and the Chesterfield Islands, in the easternmost part of the Coral Sea. It covers an area of 4,300 km2 (1,660 sq mi), making it one of the largest banks of the world, has general depths of 60 to 80 metres (197–262 ft), and a largely sandy bottom. Two reefs mark the shallowest spots of the bank, but they are still submerged at low tide.
The following outline is provided as an overview of and introduction to Oceanography.
The 1,600 kilometres (990 mi) long Macquarie Fault Zone is a major right lateral-moving transform fault along the seafloor of the south Pacific Ocean which runs from New Zealand southwestward towards the Macquarie Triple Junction. It is also the tectonic plate boundary between the Australian Plate to the northwest and the Pacific Plate to the southeast. As such it is a region of high seismic activity and recorded the largest strike-slip event on record up to May 23, 1989, of at least Mw8.0
Hotspot Ecosystem Research and Man's Impact On European Seas (HERMIONE) is an international multidisciplinary project, started in April 2009, that studies deep-sea ecosystems. HERMIONE scientists study the distribution of hotspot ecosystems, how they function and how they interconnect, partially in the context of how these ecosystems are being affected by climate change and impacted by humans through overfishing, resource extraction, seabed installations and pollution. Major aims of the project are to understand how humans are affecting the deep-sea environment and to provide policy makers with accurate scientific information, enabling effective management strategies to protect deep sea ecosystems. The HERMIONE project is funded by the European Commission's Seventh Framework Programme, and is the successor to the HERMES project, which concluded in March 2009.
The Pacific Ocean evolved in the Mesozoic from the Panthalassic Ocean, which had formed when Rodinia rifted apart around 750 Ma. The first ocean floor which is part of the current Pacific Plate began 160 Ma to the west of the central Pacific and subsequently developed into the largest oceanic plate on Earth.
The Norfolk Marine Park is an Australian marine park located in the waters immediately offshore of Norfolk Island, an external territory of Australia. The marine park extends 700 km (430 mi) in a north–south direction and covers an area of 188,444 km2 (72,759 sq mi). The park is assigned IUCN category IV and is one of 8 parks managed under the Temperate East Marine Parks Network.
The Lord Howe Marine Park is an Australian marine park located about 550 km (340 mi) offshore of New South Wales, near Lord Howe Island. The marine park covers an area of 110,126 km2 (42,520 sq mi), encompassing the smaller Lord Howe Island Marine Park, and is assigned IUCN category IV. It is one of 8 parks managed under the Temperate East Marine Parks Network.
Joseph Gilbert Seamount is a large seamount in the Tasman Sea located 450 km (280 mi) west of the South Island of New Zealand at the southern edge of the Lord Howe Rise. It has an elongated northwest–southeast trend, covering an area of about 11,500 km2 (4,400 sq mi) and rising to 2,400 m (7,900 ft) below sea level.
The geology of New Caledonia includes all major rock types, which here range in age from ~290 million years old (Ma) to recent. Their formation is driven by alternate plate collisions and rifting. The mantle-derived Eocene Peridotite Nappe is the most significant and widespread unit. The igneous unit consists of ore-rich ultramafic rocks thrust onto the main island. Mining of valuable metals from this unit has been an economical pillar of New Caledonia for more than a century.
The Lord Howe Seamount Chain of which Gifford Guyot is an eruptive centre, and part of a pair of coral-capped guyots, formed during the Miocene. The Gifford Marine Park is co-located off the Queensland coast near Brisbane.
Zealandia is an area of mostly submerged continental crust that contains New Zealand and New Caledonia.
The Three Kings Ridge, sometimes known as Three Kings Rise and more rarely at its southern end as the Three Kings Bank is a deep sea westward facing volcanic arc of Zealandia continental crust extending from 55 kilometres (34 mi) northwest of Cape Reinga / Te Rerenga Wairua, New Zealand on a line bisecting New Caledonia and Fiji in the South Pacific Ocean. Its southern portion contains the Manawatāwhi / Three Kings Islands which have biological significance as they are host to unique species and important marine ecosystems.