Adams Seamount

Adams Seamount (also known as Forty Mile Reef[2]) is a submarine volcano above the Pitcairn hotspot in the central Pacific Ocean about 100 kilometres (62 mi) southwest of Pitcairn Island.

Adams Seamount, Forty Mile Reef
Summit depth39 m (128 ft)[1]
Height3,500 m (11,500 ft)
Location
LocationPacific Ocean, SW of Pitcairn Island
Coordinates25°22′S 129°16′W
Geology
Last eruption50 BCE ± 1000 years

Geography and geomorphology

Adams is part of a field of about 90 seamounts 90 kilometres (56 mi) east-southeast away from Pitcairn Island, and the largest of these.[3] Adams lies southeast of another large seamount, Bounty Seamount.[4] Most of these seamounts except for Adams and Bounty are less than 0.5 kilometres (0.31 mi) high.[5] They were discovered in 1989 by the RV Sonne research ship.[6]

It is a conical[7] seamount rising 3,500 metres (11,483 ft) from the sea floor to about 39 metres (128 ft)[1] or 59–75 metres (194–246 ft) below the surface of the ocean.[2] The total volume of the seamount, whose base has a diameter of about 30 kilometres (19 mi), is about 858 cubic kilometres (206 cu mi).[8] Adams has two summits,[9] and coral and sand derived from coral has been found on Adams.[5] Given its height, during the last glacial maximum Adams was likely an island.[10]

Its slopes are covered by recent lava flows, volcanic debris and hyaloclastite.[9] Lava flows feature aa lava characteristics and lava tubes, while deeper parts of the edifice are covered with lapilli and scoria.[11] Parasitic vents form cones and mounds on its flanks.[12]

Geology

Adams and the other seamounts were created by the Pitcairn hotspot, and these seamounts are its present-day location.[3] This hotspot is one among several hotspots in the Pacific Ocean, along with the Austral hotspot, Hawaii hotspot, Louisville hotspot, Samoa hotspot and Society hotspot.[6] The seamounts rise from a 30 million years old crust.[13]

Alkali basalt, trachyte[9] and tholeiite have been dredged from Adams Seamount.[14]

Eruption history

The fresh appearance of samples and the lack of sedimentation indicates that Adams Seamount is a recently active seamount.[3] Potassium-argon dating of rocks dredged from Adams Seamount has yielded Holocene ages, including one age of 3,000 ± 1,000 years before present.[13] Other ages range from 4,000 - 7,000 years before present.[15] Unlike Bounty, Adams Seamount displays no active hydrothermal system.[5]

Biology

Adams seamount features a coral reef, one of the deepest tropical reefs in the world. It is mainly formed by Pocillopora sp. and Porites deformis corals, but also many reef fish and sharks; it is used as a fishing ground by Pitcairn.[2] Adams seamount is part of the Pitcairn Islands Marine Reserve.[16]

References
  1. "Adams Seamount". Global Volcanism Program. Smithsonian Institution. Retrieved 2017-02-28.
  2. Irving, Robert A.; Dawson, Terence P.; Christian, Michele (2019-01-01), Sheppard, Charles (ed.), "Chapter 34 - The Pitcairn Islands", World Seas: an Environmental Evaluation (Second Edition), Academic Press, p. 751, ISBN 9780081008539, retrieved 2019-07-27
  3. Garapić et al. 2015, p. 2.
  4. Thießen et al. 2004, p. 418.
  5. Thießen et al. 2004, p. 409.
  6. Hekinian et al. 2003, p. 220.
  7. Binard, Hékinian & Stoffers 1992, p. 261.
  8. Hekinian et al. 2003, p. 228.
  9. Binard, Hékinian & Stoffers 1992, p. 257.
  10. Neall, Vincent E.; Trewick, Steven A. (27 October 2008). "The age and origin of the Pacific islands: a geological overview". Philosophical Transactions of the Royal Society of London B: Biological Sciences. 363 (1508): 3293–3308. doi:10.1098/rstb.2008.0119. ISSN 0962-8436. PMC 2607379. PMID 18768382.
  11. Binard, Hékinian & Stoffers 1992, p. 259.
  12. Hekinian et al. 2003, p. 229.
  13. Guillou, Garcia & Turpin 1997, p. 244.
  14. Garapić et al. 2015, p. 9.
  15. Guillou, Garcia & Turpin 1997, p. 247.
  16. Albert, Donald Patrick (3 July 2018). "Did or Could Seabirds "Halo" Pitcairn Island for Fletcher Christian?". Terrae Incognitae. 50 (2): 114. doi:10.1080/00822884.2018.1498638. ISSN 0082-2884. S2CID 134051156.

Sources
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