Adams Seamount (also known as Forty Mile Reef) is a

submarine volcano Submarine volcanoes are underwater vents or fissures in the Earth's surface from which magma can erupt. Many submarine volcanoes are located near areas of tectonic plate formation, known as mid-ocean ridges. The volcanoes at mid-ocean ridges ...

above the

Pitcairn hotspot The Pitcairn hotspot is a volcanic hotspot located in the south-central Pacific Ocean. Over the past 11 million years, it has formed the Pitcairn-Gambier hotspot chain. It is responsible for creating the Pitcairn Islands and two large seamounts ...

in the central

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

about southwest of

Pitcairn Island Pitcairn Island is the only inhabited island of the Pitcairn Islands, of which many inhabitants are descendants of mutineers of HMS ''Bounty''. Geography The island is of volcanic origin, with a rugged cliff coastline. Unlike many other ...

Geography and geomorphology

Adams is part of a field of about 90

seamount A seamount is a large geologic landform that rises from the ocean floor that does not reach to the water's surface (sea level), and thus is not an island, islet or cliff-rock. Seamounts are typically formed from extinct volcanoes that rise abru ...

s east-southeast away from Pitcairn Island, and the largest of these. Adams lies southeast of another large seamount,

Bounty Seamount Bounty Seamount is a seamount in the Pacific Ocean, which reaches a depth of or . It is about high. Geology and geomorphology The seamount is part of a group of seamounts about away from Pitcairn Island, which includes several small seamoun ...

. Most of these seamounts except for Adams and Bounty are less than high. They were discovered in 1989 by the

RV Sonne The RV'' Sonne'' (German for 'Sun') was a former German fishing trawler converted into a research vessel by Schichau Unterweser AG, doing mostly geoscience-related work for a variety of commercial and scientific clients. She was registered in Bre ...

research ship. It is a conical

rising from the sea floor to about or below the surface of the ocean. The total volume of the seamount, whose base has a diameter of about , is about . Adams has two summits, and

coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and sec ...

and sand derived from coral has been found on Adams. Given its height, during the

last glacial maximum The Last Glacial Maximum (LGM), also referred to as the Late Glacial Maximum, was the most recent time during the Last Glacial Period that ice sheets were at their greatest extent. Ice sheets covered much of Northern North America, Northern Eur ...

Adams was likely an island. Its slopes are covered by recent

lava flow Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or und ...

s, volcanic debris and

hyaloclastite Hyaloclastite is a volcanoclastic accumulation or breccia consisting of glass (from the Greek ''hyalus'') fragments (clasts) formed by quench fragmentation of lava flow surfaces during submarine or subglacial extrusion. It occurs as thin margin ...

. Lava flows feature

aa lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or und ...

characteristics and

lava tube A lava tube, or pyroduct, is a natural conduit formed by flowing lava from a volcanic vent that moves beneath the hardened surface of a lava flow. If lava in the tube empties, it will leave a cave. Formation A lava tube is a type of lava ca ...

s, while deeper parts of the edifice are covered with

lapilli Lapilli is a size classification of tephra, which is material that falls out of the air during a volcanic eruption or during some meteorite impacts. ''Lapilli'' (singular: ''lapillus'') is Latin for "little stones". By definition lapilli range f ...

and

scoria Scoria is a pyroclastic, highly vesicular, dark-colored volcanic rock that was ejected from a volcano as a molten blob and cooled in the air to form discrete grains or clasts.Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, eds. (2005) ''G ...

Parasitic vents A parasitic cone (also adventive cone or satellite cone) is the cone-shaped accumulation of volcanic material not part of the central vent of a volcano. It forms from eruptions from fractures on the flank of the volcano. These fractures occur ...

form cones and mounds on its flanks.

Geology

Adams and the other seamounts were created by the

, and these seamounts are its present-day location. This hotspot is one among several hotspots in the

, along with the Austral hotspot,

Hawaii hotspot The Hawaii hotspot is a volcanic hotspot located near the namesake Hawaiian Islands, in the northern Pacific Ocean. One of the best known and intensively studied hotspots in the world, the Hawaii plume is responsible for the creation of the ...

Louisville hotspot The Louisville hotspot is a volcanic hotspot responsible for the volcanic activity that has formed the Louisville Ridge in the southern Pacific Ocean. Location The Louisville hotspot is believed to lie close to the Pacific-Antarctic Ridge, altho ...

Samoa hotspot The Samoa hotspot is a volcanic hotspot located in the south Pacific Ocean. The hotspot model describes a hot upwelling plume of magma through the Earth's crust as an explanation of how volcanic islands are formed. The hotspot idea came from ...

and

Society hotspot The Society hotspot is a volcanic hotspot in the south Pacific Ocean which is responsible for the formation of the Society Islands, an archipelago of fourteen volcanic islands and atolls spanning around 720 km of the ocean which formed between 4. ...

. The seamounts rise from a 30 million years old crust.

Alkali basalt Alkali basalt or alkali olivine basalt is a dark-colored, porphyritic volcanic rock usually found in oceanic and continental areas associated with volcanic activity, such as oceanic islands, continental rifts and volcanic fields. Alkali basalt ...

trachyte Trachyte () is an extrusive igneous rock composed mostly of alkali feldspar. It is usually light-colored and aphanitic (fine-grained), with minor amounts of mafic minerals, and is formed by the rapid cooling of lava enriched with silica and al ...

and

tholeiite The tholeiitic magma series is one of two main magma series in subalkaline igneous rocks, the other being the calc-alkaline series. A magma series is a chemically distinct range of magma compositions that describes the evolution of a mafic magma i ...

have been dredged from Adams Seamount.

Eruption history

The fresh appearance of samples and the lack of sedimentation indicates that Adams Seamount is a recently active seamount. Potassium-argon dating of rocks dredged from Adams Seamount has yielded

Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...

ages, including one age of 3,000 ± 1,000 years

before present Before Present (BP) years, or "years before present", is a time scale used mainly in archaeology, geology and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Becaus ...

. Other ages range from 4,000 - 7,000 years before present. Unlike Bounty, Adams Seamount displays no active

hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...

system.

Biology

Adams seamount features a

coral reef A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups. Co ...

, one of the deepest tropical reefs in the world. It is mainly formed by ''

Pocillopora ''Pocillopora'' is a genus of stony corals in the family Pocilloporidae occurring in the Pacific and Indian Oceans.Veron, J.E.N. (2000) Corals of the World. Australian Institute of Marine Science, Townville, Australia. They are commonly called c ...

sp.'' and '' Porites deformis'' corals, but also many reef fish and sharks; it is used as a fishing ground by Pitcairn. Adams seamount is part of the Pitcairn Islands Marine Reserve.

References

Sources

* * * * * {{refend Submarine volcanoes Hotspot volcanoes Seamounts of the Pacific Ocean Landforms of the Pitcairn Islands Former islands from the last glacial maximum