Adams Seamount
Submarine volcano above the Pitcairn hotspot in the central Pacific Ocean
From Wikipedia, the free encyclopedia
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 depth | 39 m (128 ft)[1] |
| Height | 3,500 m (11,500 ft) |
| Location | |
| Location | Pacific Ocean, SW of Pitcairn Island |
| Coordinates | 25°22′S 129°16′W |
| Geology | |
| Last eruption | 50 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]