Echo Bank

Echo Bank (also known as Endeavour Bank) is an underwater mountain southwest of the Canary Islands. Of uncertain geologic origin, it is part of a larger cluster of submarine mountains and rises to a depth of 255 metres (837 ft) below sea level. It has a flat top, indicating that it formerly might have emerged from the sea.

Echo Bank
Echo Bank
Echo Bank (North Atlantic)
North Atlantic
Summit depth255 m (837 ft)
Location
LocationNorth Atlantic
GroupCanary Islands Seamount Province
Coordinates25.40°N 19.44°W / 25.40; -19.44[1]
Geology
Volcanic arc/chainSahara Seamounts

Name

The etymology of "Echo Bank" is unknown[2] but it is also known as Endeavour Bank[3] and the name "Echo Bank" might refer to a submarine feature discovered in 1925-1927 and so named after its reflective crest.[4]

Geography and geomorphology

Regional
Map of the CISP (Rivera et al., 2016)

Echo Bank is part of the Canary Islands Seamount Province (CISP), which reaches from north of Lanzarote in the Canary Islands to southwest of the archipelago. This province aside from Echo Bank includes Tropic Seamount, The Paps Seamount, Ico Seamount and Drago Seamount but also Essaouira Seamount north of Lanzarote. Especially the southern among these underwater mountains are poorly studied;[5] together with the Canary Islands proper they form an important volcanic province in the Atlantic Ocean.[6] Aside from the seamounts, submarine canyons and large debris flows occur in the region[7] such as the Sahara Slide which has run around Echo Bank.[8]

Local

Echo Bank rises from the continental slope to a depth of about 300 metres (980 ft) below sea level, making it the shallowest seamount in the region.[7] It has a maximally 16 kilometres (9.9 mi) wide flat top like a guyot at a depth of 350 metres (1,150 ft) that is surmounted by volcanic cones which reach depths of 255 metres (837 ft) and also by small depressions;[1] the cones cluster in the central summit platform.[9] Around the summit lie terraces and scarps, with the terraces particularly pronounced on the eastern side[1] and perhaps reflecting a slight tilt of the seamount.[10] The slopes of the seamount are steep and cut by curved slide scars and gullies which both reach lengths of 12–13 kilometres (7.5–8.1 mi). Echo Bank is 40 by 34 kilometres (25 mi × 21 mi) wide with a round shape and a 20 kilometres (12 mi) long ridge to the northwest and rests on a seafloor with a minimum depth of 3,700 metres (12,100 ft).[1]

Northwest of Echo Bank lies first at 90 kilometres (56 mi) distance[11] The Paps Seamount and after a group of submarine hills comes Ico Seamount, while southwest lies Drago Seamount and south-southwest lies Tropic Seamount[7] 200 kilometres (120 mi) away.[11] Northeast from Echo Bank lies first Hierro Seamount and then the island of El Hierro.[12]

Geology

The geological origin of the Canary Islands Seamounts are unclear, with various hotspot processes as well as crustal and mantle phenomena proposed.[7] Volcanic activity at Echo and Tropic seamounts was probably focused and generated a circular volcanic structure, while at Drago and The Paps it was controlled by lineaments and thus formed elongated edifices.[13]

Composition

Dredging at Echo Bank has yielded basaltic lapillistones, carbonates, coral debris, intermediate volcanic rocks, limestone of hemipelagic origin, manganese crusts, sandstone of volcanic and calcarenite origin and vesicular basalt.[14] The volcanic rocks at the Canary Islands seamounts like those of the Canary Islands are classified as alkalic;[6] the basaltic rocks contain clinopyroxene while the rare intermediary volcanic rocks contain amphibole.[11]

Dredged samples of the ferromanganese crusts consist mainly of goethite and manganese dioxide and minor amounts of calcite, phyllosilicate and quartz.[15] The ferromanganese deposits which occur on the Canary Islands Seamounts including at Echo Bank reach thicknesses of 20 centimetres (7.9 in) and are rich in cobalt[16] and other elements of industrial significance; thus such submarine deposits have been considered to be targets for future mining efforts.[6]

Environment

A number of separate water masses surround Echo Bank, which originate from regions such as the North Atlantic, the South Atlantic and Antarctica and are stacked over each other.[7] In general, the region is under the influence of the nutrient-poor waters of the subtropical gyre and the upwelling regions off northwestern Africa.[6]

Bottom net trawlings of Echo Bank have revealed remarkable findings[17] such as a rich decapod fauna.[18] African cuttlefish,[19] the barnacle Poecilasma aurantia,[20] the common cuttlefish,[21] the elegant cuttlefish[22] and the giant African cuttlefish occur at Echo Bank; the giant African cuttlefish is the most commercially important cuttlefish in the region.[23] In addition, the bobtail squids Rossia and Sepiola[24] and the ram's horn squid have been found at Echo Bank.[25] Shoals of fish were frequently observed on the seamount.[26] In 1960–1970, snapper fisheries at Echo Bank were replaced by cephalopod fisheries.[27]

Geologic history

The flat top of Echo Bank has been interpreted as having formed during subaerial erosion, implying that the seamount was once an island although the evidence for such is less clear than at Tropic Seamount[10] and alternative explanations for the flat summit exist.[13] Echo Bank is currently undergoing sedimentation and it appears to be volcanically inactive.[8]

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References
  1. Palomino et al. 2016, p. 128.
  2. SCUFN 2003, p. 4.
  3. SCUFN 2003, p. 43.
  4. Egloff, Julius (1972). "Morphology of Ocean Basin Seaward of Northwest Africa: Canary Islands to Monrovia, Liberia". AAPG Bulletin. 56 (4): 702. ISSN 0149-1423.
  5. Palomino et al. 2016, p. 125.
  6. Marino et al. 2017, p. 42.
  7. Palomino et al. 2016, p. 126.
  8. Palomino et al. 2016, p. 135.
  9. Palomino et al. 2016, p. 131.
  10. Palomino et al. 2016, p. 134.
  11. Schmincke & Graf 2000, p. 38.
  12. Schmincke & Graf 2000, p. 2.
  13. Palomino et al. 2016, p. 133.
  14. Schmincke & Graf 2000, p. 75.
  15. Marino et al. 2017, p. 47.
  16. Torres Pérez-Hidalgo, Trinidad José; Ortiz Menéndez, José Eugenio; González, F.J.; Somoza, L.; Lunar, R.; Martínez-Frías, J.; Medialdea, T.; León, R.; Martín-Rubí, J.A.; Marino, E. (2014). Polymetallic ferromanganese deposits research on the Atlantic Spanish continental margin. Harvesting Seabed Minerals Resources in Harmony with Nature UMI 2014. Lisboa. p. 7 – via Academia.edu.
  17. NATIONAL INSTITUTE OF OCEANOGRAPHY 1970, p. 2.
  18. NATIONAL INSTITUTE OF OCEANOGRAPHY 1970, p. 16.
  19. Jereb & Roper 2005, p. 74.
  20. Southward, Alan J.; Lorenzo, José M.; Martín-García, Laura; Shalaeva, Kate; González, José A. (1 January 2017). "First account on deep-sea stalked barnacles from the Canary Islands (NE Atlantic), with an updated checklist of the Cirripedia, Thoracica and their hosts in the area". Crustaceana. 90 (13): 1579. doi:10.1163/15685403-00003708. ISSN 1568-5403.
  21. Jereb & Roper 2005, p. 100.
  22. Jereb & Roper 2005, p. 80.
  23. Jereb & Roper 2005, p. 88.
  24. Clarke 2006, p. 41.
  25. Clarke 2006, p. 37.
  26. Hargreaves, P. M. (1 February 1975). "Some observations on the relative abundance of biological sound scatters in the North-eastern Atlantic Ocean, with particular reference to apparent fish shoals". Marine Biology. 29 (1): 84. doi:10.1007/BF00395529. ISSN 1432-1793.
  27. Jereb & Roper 2005, p. 18.

Sources
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