Rockall Basin

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Bathymetric features to the northwest of Scotland and Ireland Rockall Trough.jpg
Bathymetric features to the northwest of Scotland and Ireland
North Atlantic around Iceland N-Atlantic-topo.png
North Atlantic around Iceland

The Rockall Trough (Scottish Gaelic : Clais Sgeir Rocail) is a deep-water bathymetric feature to the northwest of Scotland and Ireland, running roughly from southwest to northeast, flanked on the north by the Rockall Plateau and to the south by the Porcupine Seabight. At the northern end, the channel is bounded by the Wyville-Thomson Ridge, named after Charles Wyville Thomson, professor of zoology at the University of Edinburgh and driving force behind the Challenger Expedition. At the southern end, the trough opens into the Porcupine abyssal plain. The Rockall Basin (also known as the Hatton Rockall Basin) is a large (c. 800 km by 150 km) sedimentary basin that lies beneath the trough. Both are named after Rockall, a rocky islet lying 301.4 km west of St Kilda.

Contents

Features of the Rockall Plateau have been officially named after features of Middle-earth in the fiction of J. R. R. Tolkien, e.g. Eriador Seamount, Rohan Seamount, Gondor Seamount, Fangorn Bank, Edoras Bank, Lorien Knoll, Isengard Ridge. [1]

In February 2000, the RRS Discovery , a British oceanographic research vessel sailing in the Rockall Trough encountered the largest waves ever recorded by scientific instruments in the open ocean, with a SWH of 18.5 metres (61 ft) and individual waves up to 29.1 metres (95 ft). [2]

Geological structure

The nature of the crust beneath the Rockall Trough has long been a matter of debate. Originally thought to be oceanic crust it is now generally considered to be highly stretched continental crust, although some groups of researchers continue to favour either oceanic or transitional style crust, particularly at the southern end of the basin.

The Rockall Basin forms part of a chain of highly extended Mesozoic rift basins between the Charlie-Gibb and Senja Fracture Zones, that includes; the Faroe-Shetland Basin, the Møre Basin, and the Vøring Basin. There are indications that the Rockall Basin developed within an earlier rift system, which is likely to be of Triassic to Middle Jurassic in age, by analogy with the nearby Slyne-Erris Basins. The age of the main rift phase in the Rockall Basin is strongly debated, with Late Jurassic, Early-, Mid- and Late Cretaceous all being suggested.

One of the features of the Rockall Trough is the Anton Dohrn Seamount. It lies 600 metres (2,000 ft) beneath the surface, rising 1,500 metres (4,900 ft) from the surrounding seabed. The plateau formed approximately 55 million years ago, a continental fragment formed between Greenland and Europe when the ancient continent of Laurasia was split apart by plate tectonics. [3] The Rockall Islet is the highest point of the plateau, rising 21 m above sealevel. It is made of a type of peralkaline granite.

Economic geology

To date, there has been comparatively little drilling to explore for oil and gas within the Rockall Basin and only two discoveries have been made, Benbecula in the northern UK Rockall (Shell originally Enterprise Oil) and Dooish in the northern Irish Rockall (Shell originally Enterprise Energy Ireland). The discoveries show that, at least locally, there is a working petroleum system. Rights to exploit these resources are disputed between the United Kingdom, the Republic of Ireland, Iceland and the Faroe Islands (a possession of Denmark). This topic is addressed in Rockall Bank dispute.

Ecology

Hatton-Rockall Basin MPA
IUCN category IV (habitat/species management area)
Rockall-Hatton Basin MPA.png
The location and extent of the Hatton-Rockall Basin MPA, shown in red
Location North Atlantic, Scotland
Area1,256 km2 (485 sq mi) [4]
Designation Scottish Government
Established2014
Operator Marine Scotland

The area supports cold-water coral colonies and carbonate mound fields such as the Logachev Mounds; the trough supports a rich deep sea fish population. [5] There are also unusual aggregations of deep-sea sponges, in particular the encrusting sponge and bird's nest sponge. A range of other species are found amongst the sponges beds, which are considered biodiversity hotspots. For the bird's nest sponge associated species include ascidians, Foraminifera, polychaetes and burrowing anemones, whilst for the encrusting sponge beds species such as anemones, ascidians, crinoids and ophiuroids are found. The area is also home to brittlestars: filter feeders which live on the seabed. [6]

In 2014 an area of 1,256 square kilometres (485 sq mi) of the Hatton-Rockall Basin was declared a Nature Conservation Marine Protected Area. [4] The MPA is designated a Category IV protected area by the International Union for Conservation of Nature. [7]

See also

Related Research Articles

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<span class="mw-page-title-main">Wyville Thomson Ridge</span> Feature of the North Atlantic Ocean floor between the Faroe Islands and Scotland

The Wyville Thomson Ridge is a bathymetric feature of the North Atlantic Ocean floor ca. 200 km in length, located between the Faroe Islands and Scotland. The ridge separates the Faroe–Shetland Channel to the north from the Rockall Trough to the south. Its significance lies in the fact that it forms part of the barrier between the colder bottom waters of the Arctic and the warmer waters of the North Atlantic.

The Slyne-Erris Trough is a geological basin off the west coast of Donegal, Ireland.

The Hatton Basin is a ca. 600 km long SW–NE trending sedimentary basin, located off the west coast of Ireland. It lies between the Hatton and Edoras Banks to the west and the Rockall Bank to the east. The basin contains about 4,000 m of sediments of probable Cretaceous to Cenozoic age. Its relationship to the Rockall Basin remains uncertain.

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<span class="mw-page-title-main">Anton Dohrn Seamount</span> Guyot in the Rockall Trough in the northeast Atlantic

The Anton Dohrn Seamount is a guyot in the Rockall Trough in the northeast Atlantic. It is 1.8 kilometres (1.1 mi) high and is topped with pinnacles, one of which reaches a depth of 530 metres (1,740 ft). Away from the flat top upon which the pinnacles rest, the slopes fall off steeply into the Rockall Trough and a moat in the sediment that surrounds the seamount.

<span class="mw-page-title-main">Porcupine Seabight</span> Deep-water oceanic basin on the continental margin of the northeastern Atlantic

The Porcupine Seabight or Porcupine Basin is a deep-water oceanic basin located on the continental margin in the northeastern portion of the Atlantic Ocean. It can be found in the southwestern offshore portion of Ireland and is part of a series of interconnected basins linked to a failed rift structure associated with the opening of the Northern Atlantic Ocean. The basin extends in a North-South direction and was formed during numerous subsidence and rifting periods between the Late Carboniferous and Late Cretaceous. It is bordered by the

<span class="mw-page-title-main">Porcupine Bank</span> Area of the Atlantic Ocean

Porcupine Bank is an area of the Irish shelf, on the fringes of the Atlantic Ocean approximately 200 kilometres (120 mi) west of Ireland. The relatively raised area of seabed, 200 m below sea level at its highest, lies between the deep-water Porcupine Seabight and Rockall Trough.

<span class="mw-page-title-main">Orca Seamount</span> Underwater volcano near King George Island in Antarctica, in the Bransfield Strait.

Orca Seamount is a seamount near King George Island in Antarctica, in the Bransfield Strait. While it is inactive, last volcanic activity at Orca Seamount is judged to have occurred in the recent past as there are temperature anomalies in the seawater around the seamount. Thermophilic and hyperthermophilic microorganisms have been found at the seamount.

Rosemary Bank is a seamount approximately 120 kilometres (75 mi) west of Scotland, located in the Rockall Trough, in the northeast Atlantic. It was discovered in 1930 by the survey vessel HMS Rosemary, from which it takes its name. It is one of only three seamounts known in Scottish waters.

<span class="mw-page-title-main">East Tasman Plateau</span> Submerged microcontinent south east of Tasmania

The East Tasman Plateau is a submerged microcontinent south east of Tasmania. Its area is 50,000 square kilometres (19,000 sq mi), and it is mostly from 2,500 to 3,000 metres deep. It is a circular piece of continental rocks surrounded by oceanic crust. Volcanism occurred there 36 million years ago. The East Tasman Plateau is separated from the island of Tasmania by 100 kilometres (62 mi) of deeper water, and the East Tasman Saddle is a higher ridge connecting the plateau to the Freycinet Peninsula region of the Tasmanian East Coast. This ridge runs north west from the plateau. South-west of the plateau is the L'Atalante Depression. The East Tasman Plateau represents a continental fragment.

<span class="mw-page-title-main">Charlie-Gibbs Fracture Zone</span> Oceanic feature on the Mid-Atlantic Ridge

Charlie-Gibbs Fracture Zone is a system of two parallel fracture zones. It is the most prominent interruption of the Mid-Atlantic Ridge between the Azores and Iceland, with the longest faults in the North Atlantic, and is ecologically an important biosystems boundary. It can be traced over more than 2,000 kilometres (1,200 mi), from north-east of Newfoundland to south-west of Ireland. It took 90 million years for the fault to grow to this length.

The Wallaby Plateau, which is also known as the Cuvier Plateau, is a large bathymetric high about 450 kilometres (280 mi) west of Carnarvon, Western Australia. The Wallaby Plateau covers approximately 100,000 km2 (39,000 sq mi) and is in water depths of 2,200 meters (7,200 ft) to greater than 5,000 meters (16,000 ft). In the west, the Wallaby Plateau is separated from the Zenith Plateau by a 100–150-kilometre (62–93 mi) wide, north to northeast-trending bathymetric trough. Wallaby Plateau is the name used by the Australian geologists and government for this undersea plateau. This name was first used in a Hartog AGSO bathymetric map and formally recognized in a peer-reviewed paper by Symonds and Cameron in 1977. In contrast, the internationally recognized name for it is Cuvier Plateau. Cuvier is a historical name that is presumably derived from the adjacent Cape Cuvier. Cape Cuvier was named for Georges Cuvier, zoologist and statesman, by a French expedition led by Baudin in 1800–1803. The Wallaby Plateau lies inside the Australian Exclusive Economic Zone.

The Zenith Plateau is a large bathymetric high in the Indian Ocean, located about 450 kilometres (280 mi) west-northwest of the Wallaby Plateau, 1,400 kilometres (870 mi) west-northwest of Carnarvon, Western Australia, and 1,700 kilometres (1,100 mi) north-west of Perth, Western Australia. The summit of the Zenith Plateau lies 1,960 meters (6,430 ft) below sea level and its base is at about 5,000 meters (16,000 ft) below sea level. It is about 300 kilometres (190 mi) long and 200 kilometres (120 mi) wide. In the east, the Zenith Plateau is separated from the Wallaby (Cuvier) Plateau by a 100–150 kilometres (62–93 mi) wide, north to northeast-trending bathymetric trough. The Zenith Plateau lies outside of the Australian Exclusive Economic Zone.

<span class="mw-page-title-main">Louisiade Plateau</span> Underwater plateau in the South Pacific Ocean

The Louisiade Plateau, also called the Louisiade Rise, is a poorly studied oceanic plateau in the northern Coral Sea of the South Pacific Ocean. To its west is the Louisiade Archipelago that it is named after. It has been described as a continental fragment that rifted away from the northwestern continental margin of Australia but its position at the northern end of the Tasmantid Seamount Chain also suggests that the Louisiade Plateau might be a large igneous province formed by the arrival of the Tasmantid hotspot. A sample of volcanic rock from the southern spur of the Louisiade Plateau was dated at 56.4 ± 0.6 million years ago by Ar-Ar methodology which is not inconsistent with Tasmantid Seamount Chain timings. Recent sampling however along the northernmost part of the plateau found serpentinized peridotites, mid-ocean ridge basalt and volcaniclastic breccia–conglomerates consistent with placement of oceanic crust during a subduction initiation event in the formation of this part of the plateau.

<span class="mw-page-title-main">Faroe–Shetland Channel</span> Area of the north Atlantic to the north of Scotland

The Faroe–Shetland Channel is stretch of the North Atlantic lying between the two island groups of Shetland and the Faroe Islands. The channel is a rift basin that separates the Scottish and the Faroese continental shelves, and has a maximum depth of 1900 m, compared to the surrounding seabed which mostly lies at 200 m. It was first noted by Charles Wyville Thomson during the mid-nineteenth century.

<span class="mw-page-title-main">Barra Fan and Hebrides Terrace Seamount Marine Protected Area</span> Seabed features in the North Atlantic

The Barra Fan and Hebrides Terrace Seamount is the name given to a Nature Conservation Marine Protected Area that lies in Scottish waters to the west of the Outer Hebrides, adjacent to the boundary with Ireland. It covers two distinct geological features of the North Atlantic Ocean: the Barra Fan and the Hebrides Terrace Seamount.

Hebrides Terrace Seamount is a seamount in the Atlantic Ocean, west-southwest from the Hebrides, Scotland. It formed through volcanism during the early Cenozoic in the Rockall Trough 60 million to 67 million years ago and afterwards sank below sea level. Presently, it is a flat-topped underwater mountain that rises to about 980 metres depth. "Coral gardens" that host a number of animals are found on its slopes.

<span class="mw-page-title-main">West of Scotland Marine Protected Area</span> Area of the North North Atlantic

The West of Scotland Marine Protected Area covers a large area of the North Atlantic to the west of the Outer Hebrides. The Marine Protected Area (MPA) was designated by the Scottish Government in 2020, replacing the Rosemary Bank MPA, which covered a much smaller area. Covering a sea area of over 100,000 square kilometres (39,000 sq mi), it is the largest marine protected area in Europe.

References

  1. ↑ General Bathymetric Chart of the Ocean Sub-Committee on Undersea Feature Names. "International Hydro-graphic Organization-Intergovernmental Oceanographic Commission General Bathymetric Chart of the Ocean (IHO-IOC GEBCO) Gazetteer of Undersea Feature Names" http://www.gebco.net/data_and_products/undersea_feature_names/
  2. ↑ Holliday, NP, MJ Yelland, RW Pascal, VR Swail, PK Taylor, CR Griffiths, and EC Kent (2006). Were extreme waves in the Rockall Trough the largest ever recorded? Geophysical Research Letters, Vol. 33, L05613
  3. ↑ Igneous Rocks of the British Isles edited by D.S. Sutherland, 1982, Wiley
  4. 1 2 "Hatton-Rockall Basin MPA(NC)". NatureScot. Retrieved 11 October 2020.
  5. ↑ WWF Brasil. "Map of Proposed MPAs" . Retrieved 27 January 2008.[ dead link ]
  6. ↑ "Hatton-Rockall Basin MPA(NC)". Joint Nature Conservation Committee. Retrieved 24 October 2019.
  7. ↑ "Hatton-Rockall Basin in United Kingdom of Great Britain and Northern Ireland". Protected Planet. Retrieved 24 October 2019.

55°00′N14°00′W / 55.000°N 14.000°W / 55.000; -14.000

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