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.
The Hebrides Terrace Seamount is a volcanic[7]guyot, a seamount with a flat top and steep slopes,[1] that rises to a depth of about 980 metres (3,220 ft).[8] It is about 28 by 37 kilometres (17 mi × 23 mi) wide at its basis[3] and its southern and western flanks feature canyons, escarpments and gullies. The surrounding terrain at 2,300 metres (7,500 ft) depth is covered by debris of Plio-Pleistocene age; the debris deposits are almost 1 kilometre (0.62 mi) thick.[2] The Barra and Donegal fans, two sediment fans that form a larger complex, border the Hebrides Terrace Seamount to the north and south, respectively.[9] The seamount has diverted sediment flows,[10] leading to the formation of these two fans[11] and the accumulation of sediments east of Hebrides Terrace Seamount.[12]
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.[2] The volcanism may be correlative to the early Cenozoic Hebridean volcanic province.[16] Ages of 67-60 million years have been obtained on Hebrides Terrace Seamount,[17] as well as
62±1, 51±1 and 48±1 million years ago which coincide with activity at Anton Dohrn Seamount.[18] These dates have been interpreted as indicating fluctuations of the Iceland hotspot.[19]
After the end of volcanic activity, its top was flattened perhaps by Paleocene erosion that has been recognized in the region[7] although other processes may be involved as well.[16] 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.[20]
Evidence of more recent seismic activity is found along its southern slopes.[2] On 13 April 1980 a ML 3.5 earthquake[21] occurred just west of Hebrides Terrace Seamount;[22] it was probably not an underwater explosion and may have been instead caused by movements along a local fault.[23]Isostatic processes may have caused the earthquake.[24] Another ML 3.1 earthquake occurred south of the seamount in 1986.[25]
^Sacchetti, F.; Benetti, S.; Georgiopoulou, A.; Shannon, P. M.; O'Reilly, B. M.; Dunlop, P.; Quinn, R.; Ó Cofaigh, C. (1 January 2012). "Deep-water geomorphology of the glaciated Irish margin from high-resolution marine geophysical data". Marine Geology. 291–294: 114. Bibcode:2012MGeol.291..113S. doi:10.1016/j.margeo.2011.11.011. ISSN0025-3227.
El-Tokhi, M.; Omran, M.; El-Muslem, A. (1 January 2005). "Geochemistry of Late Cretaceous (60–67 Ma) igneous activities in the hebrides terrace seamount (guyot) area, Scotland". Chinese Journal of Geochemistry. 24 (1): 9–17. doi:10.1007/BF02869684. ISSN1993-0364. S2CID129235924.