Английская Википедия:Hebrides Terrace Seamount
Шаблон:Short description Шаблон:Infobox 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 (3,220 ft) depth. "Coral gardens" that host a number of animals are found on its slopes.
Geography and geomorphology
The seamount lies in the southern Rockall Trough,Шаблон:Sfn at the foot of the Scottish continental slope and Шаблон:Convert west-southwest of Barra Head, Hebrides.Шаблон:Sfn It is the smallest of three seamounts in the Rockall Trough;Шаблон:Sfn the other two are Anton Dohrn Seamount and Rosemary Bank both north of Hebrides Terrace Seamount,Шаблон:Sfn and farther west is the Rockall Bank.Шаблон:Sfn It straddles the political border between the United Kingdom and Ireland.[1]
The Hebrides Terrace Seamount is a volcanicШаблон:Sfn guyot, a seamount with a flat top and steep slopes,Шаблон:Sfn that rises to a depth of about Шаблон:Convert.[2] It is about Шаблон:Convert wide at its basisШаблон:Sfn and its southern and western flanks feature canyons, escarpments and gullies. The surrounding terrain at Шаблон:Convert depth is covered by debris of Plio-Pleistocene age; the debris deposits are almost Шаблон:Convert thick.Шаблон:Sfn The Barra and Donegal fans, two sediment fans that form a larger complex, border the Hebrides Terrace Seamount to the north and south, respectively.Шаблон:Sfn The seamount has diverted sediment flows,Шаблон:Sfn leading to the formation of these two fansШаблон:Sfn and the accumulation of sediments east of Hebrides Terrace Seamount.[3]
Rocks dredged from Hebrides Terrace Seamount have a tholeiiticШаблон:Sfn basaltic composition and define two separate suites, one aluminium-rich and the other aluminium-poor. They contain phenocrysts of augite, olivine, pigeonite, plagioclase and titanomagnetite, which together with ilmenite and pyroxene also occur in the groundmass.Шаблон:Sfn The seamount is the location of a positive gravity anomaly that is thought to indicate the presence of a Шаблон:Convert thick igneous body.[4]
Geologic history
The formation of the Hebrides Terrace Seamount began after the Cretaceous-Palaeogene extinction event. In the early Cenozoic, three pulses of volcanic activity generated the seamount.Шаблон:Sfn The volcanism may be correlative to the early Cenozoic Hebridean volcanic province.Шаблон:Sfn Ages of 67-60 million years have been obtained on Hebrides Terrace Seamount,Шаблон:Sfn as well as 62±1, 51±1 and 48±1 million years ago which coincide with activity at Anton Dohrn Seamount.Шаблон:Sfn These dates have been interpreted as indicating fluctuations of the Iceland hotspot.Шаблон:Sfn
After the end of volcanic activity, its top was flattened perhaps by Paleocene erosion that has been recognized in the regionШаблон:Sfn although other processes may be involved as well.Шаблон:Sfn This along with subsidence during the Eocene, Oligocene and in a lesser measure during the Miocene and later time lowered its summit below sea level.Шаблон:Sfn
Evidence of more recent seismic activity is found along its southern slopes.Шаблон:Sfn On 13 April 1980 a Шаблон:M earthquakeШаблон:Sfn occurred just west of Hebrides Terrace Seamount;Шаблон:Sfn it was probably not an underwater explosion and may have been instead caused by movements along a local fault.Шаблон:Sfn Isostatic processes may have caused the earthquake.[5] Another Шаблон:M earthquake occurred south of the seamount in 1986.[6]
Life
Xenophyophores (mainly Syringammina fragilissima), sponges and corals (such as Solenosmilia variabilis) occur on Hebrides Terrace Seamount,Шаблон:Sfn principally on its slopes,Шаблон:Sfn and form so-called "coral gardens".[7] These also host black corals, crinoids, egg cases of elasmobranchs, glass sponges and ophiuroids.Шаблон:Sfn The faunal communities vary depending on the depth, the substrate (bedrock, cobbles, corals, gravel and sand), the nature of the watermass surrounding themШаблон:Sfn and internal tides which modulate the nutrient supply.Шаблон:Sfn The complicated oceanographic regime may facilitate the concentration of nutrients at the seamount, enabling the development of rich biological communities.Шаблон:Sfn
Beaked whales, fin whales, harbour porpoises, long-finned pilot whales have been sighted on the seamount.Шаблон:Sfn Fish species encountered at Hebrides Terrace Seamount include Atlantic codling, false boarfish and roundnose grenadier.[8] Overfishing has decimated orange roughy spawning aggregations that formerly occurred at Hebrides Terrace Seamount.Шаблон:Sfn Sharks and other fish have also declined since the 1970s.Шаблон:Sfn
Marine Protected Area
The Hebrides Terrace Seamount, together with a nearby seabed feature known as the Barra Fan, are together designated by the Scottish Government as a Nature Conservation Marine Protected Area named the Barra Fan and Hebrides Terrace Seamount Marine Protected Area.[9]
References
Sources
- Шаблон:Cite journal
- Шаблон:Cite journal
- Шаблон:Cite journal
- Шаблон:Cite journal
- Шаблон:Cite journal
- Шаблон:Cite journal
- Шаблон:Cite journal
