A seamount is a mountain rising from the ocean seafloor that does not reach to the water's surface (sea level), and thus is not an island. These are typically formed from extinct volcanoes, that rise abruptly and are usually found rising from a seafloor of 1,000 - 4,000 meters depth. They are defined by oceanographers as independent features that rise to at least 1,000 meters above the seafloor. The peaks are often found hundreds to thousands of meters below the surface, and are therefore considered to be within the deep sea.^[1] An estimated 30,000 seamounts occur across the globe, with only a few having been studied. Lyskamm, 4 527 m, Pennine Alps A mountain is a landform that extends above the surrounding terrain in a limited area. ... Animated map exhibiting the worlds oceanic waters. ... The seabed (also sea floor, seafloor, or ocean floor) is the bottom of the ocean. ... For considerations of sea level change, in particular rise associated with possible global warming, see sea level rise. ... Thermohaline circulation Oceanography (from Ocean + Greek γράφειν = write), also called oceanology or marine science, is the branch of Earth Sciences that studies the Earths oceans and seas. ... The term deep sea refers to those areas of oceans to which little or no light penetrates (the aphotic zone). ...

Geography

The locations of the world's major seamounts

Seamounts are often found in groupings or submerged archipelagos, a classic example being the Emperor Seamounts, which are an extension of the Hawaiian Islands, which were formed millions of years ago by volcanism, and have since subsided to below sea level. The long chain of islands and seamounts, extending thousands of kilometres northwest from the Big Island demonstrates the movement of a plate over a volcanic hotspot. Image File history File links Size of this preview: 800 × 370 pixelsFull resolution (1357 × 628 pixel, file size: 25 KB, MIME type: image/png) I, the creator of this work, hereby grant the permission to copy, distribute and/or modify this document under the terms of the GNU Free Documentation... Image File history File links Size of this preview: 800 × 370 pixelsFull resolution (1357 × 628 pixel, file size: 25 KB, MIME type: image/png) I, the creator of this work, hereby grant the permission to copy, distribute and/or modify this document under the terms of the GNU Free Documentation... The Mergui Archipelago An archipelago is a landform which consists of a chain or cluster of islands. ... The Emperor Seamounts are a chain of seamounts (submerged volcanic mountains) extending from the northwestern Hawaiian Islands (see Kure and Midway atolls) in a northwesterly direction until approximately 170º east longitude where they trend abruptly northward towards the tip of the Aleutian Islands and the Kamchatka Peninsula. ... Map of the Hawaiian Islands, a chain of islands that stretches 2,400 km in a northwesterly direction from the southern tip of the Island of Hawai‘i. ... This article is about volcanoes in geology. ... The Island of HawaiÊ»i (called the Big Island or HawaiÊ»i proper) is one of eight main islands that make up the U.S. state of HawaiÊ»i. ... The tectonic plates of the world were mapped in the second half of the 20th century. ... In geology, a hotspot is a location on the Earths surface that has experienced active volcanism for a long period of time. ...

Isolated seamounts and those without clear volcanic origins appear to be less common. In recent years, geologists have confirmed that a number of seamounts are active undersea volcanoes: Lo‘ihi in the Hawaiian Islands and Vailu‘ulu‘u in the Manu‘a Group (Samoa) are examples. For other uses, see Volcano (disambiguation). ... For other uses, see Volcano (disambiguation). ... Lo‘ihi seamount is an undersea volcano in the Hawaiian archipelago. ... The Islands of Ofu and Olosega viewed from the village of Sili along the north shore of Olosega. ...

Ecology

Seamounts often project upwards into shallower zones more hospitable to sea life, providing habitats for marine species that are not found on or around the surrounding deeper ocean bottom. Because seamounts are isolated from each other they form "undersea islands" creating the same biogeographical interest. As they are formed from volcanic rock, the substrate is much harder than the surrounding sedimentary deep sea floor. This causes a different type of fauna to exist than on the seafloor, and leads to a higher degree of endemism. Habitat (which is Latin for it inhabits) is the place where a particular species live and grow. ... Biogeography is the science which deals with questions of the distribution of species usually at regional to continental scales. ... Endemic, in a broad sense, can mean belonging or native to, characteristic of, or prevalent in a particular geography, race, field, area, or environment; Native to an area or scope. ...

In addition to simply providing physical presence in this zone, the seamount itself may deflect deep currents and create upwelling. This process can bring nutrients into the photosynthetic zone, producing an area of activity in an otherwise desert-like open ocean. Seamounts may thus be vital stopping points for some migratory animals such as whales. Some recent research indicates whales may use such features as navigational aids throughout their migration. Due to the larger populations of fish in these areas overexpoitation by the fishing industry has caused some seamount fauna populations to decrease considerably. Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water towards the ocean surface, replacing the warmer, usually nutrient-deplete surface water. ... A Fin Whale The term whale is ambiguous: it can refer to all cetaceans, to just the larger ones, or only to members of particular families within the order Cetacea. ...

The primary productivity of the epipelagic waters above the submerged peak can often be enhanced by the hydrographic conditions of the seamount.^[2] This increases the densities of the zooplankton and leads to the high concentrations of fish in these areas. Another theory for this is that the fish are sustained on the diurnal migration of zooplankton being interrupted by the presence of the seamount, and causing the zooplankton to stay in the area. It is also possible that the high densities of fishes has more to do with the fish life histories and interaction with the benthic fauna of the seamount.^[3] The benthic fauna of the seamounts is dominated by suspension feeders, including sponges and true corals. For some seamounts that peaks at 200-300 metres below the surface benthic macroalgae is common. The sedimentary infauna is dominated by polychaete worms. The pelagic zone is the part of the open sea or ocean comprising the water column, i. ... Hydrography is the measurement of physical characteristics of waters and marginal land. ... Photomontage of plankton organisms Plankton is the aggregate community of weakly swimming but mostly drifting small organisms that inhabit the water column of the ocean, seas, and bodies of freshwater. ... Classes Calcarea Hexactinellida Demospongiae The sponges or poriferans (from Latin porus pore and ferre to bear) are animals of the phylum Porifera. ... Extant Subclasses and Orders Alcyonaria    Alcyonacea    Helioporacea Zoantharia    Antipatharia    Corallimorpharia    Scleractinia    Zoanthidea [1][2]  See Anthozoa for details For other uses, see Coral (disambiguation). ... Subclasses Palpata Scoleoida Tomopteris from plankton The Polychaeta or polychaetes are a class of annelid worms, generally marine. ...

In 2005 a Census of Marine Life project "CenSeam" (a global census of marine life on seamounts) was formed. CenSeam is intended to provide the framework needed to prioritise, integrate, expand and facilitate seamount research efforts in order to significantly reduce the unknown and build towards a global understanding of seamount ecosystems, and the roles they have in the biogeography, biodiversity, productivity and evolution of marine organisms. CenSeam researchers have identified two core research themes – (1): What factors drive community composition and diversity on seamounts, including any differences between seamounts and other habitat types? And (2): What are the impacts of human activities on seamount community structure and function?

Fishing

The main cause for the recent interest in seamounts is the discovery that they maintain large stocks of commercially important fishes and invertebrates. This began during the 1960s when Russia, Australia and New Zealand started to look for new stocks of fish and began to trawl the seamounts. The majority of the invertebrates brought up are corals, and are mainly used for the jewelry trade. The two major fish species were the orange roughy (Hoplostethus atlanticus) and pelagic armourhead (Pseudopentaceros wheeleri), which were quickly overexploited due to lack of knowledge of the longevity of the fish, late maturity, low fecundity, small geographic range and recuitment to the fishery. As well as the fishes being overexploited the benthic communities were destroyed by the trawling gear. 1960 (MCMLX) was a leap year starting on Friday (the link is to a full 1960 calendar). ... Binomial name Hoplostethus atlanticus Collett, 1889 The orange roughy, red roughy, or deep sea perch[2][3] Hoplostethus atlanticus, is a relatively large deep-sea fish belonging to the slimehead family (Trachichthyidae). ... Binomial name (Smith, 1844) The pelagic armorhead, pelagic armourhead, Richardsons boarfish, or southern boarfish, Pseudopentaceros richardsoni, is an armorhead of the genus Pseudopentaceros, found in the north and south Pacific Ocean, South Africa, South America, and the South Island of New Zealand, from the surface to depths of 300... Fecundity is the potential reproductive capacity of an organism or population, measured by the number of gametes (e. ...

One of the core research themes of CenSeam (a Census of Marine Life project - see link below) is the impact of human activities (e.g. fishing) on seamount community structure and function. CenSeam's Data Analysis Working Group recently assessed the vulnerability of deep-sea corals to fishing on seamounts beyond areas of national jurasdiction (Clark et al. 2006 - see external links).

Dangers

Some seamounts have not been mapped and thus pose a navigational danger. For instance, Muirfield Seamount is named after the ship that hit it in 1973. More recently, the USS San Francisco (SSN-711) submarine ran into an uncharted seamount in 2005 at a speed of 35 knots, sustaining serious damage and killing one seaman. The Muirfield Seamount is a submarine mountain located in the Indian Ocean approximately 130 kilometers (70 nautical miles) southwest of the Cocos (Keeling) Islands. ... USS San Francisco (SSN-711), a Los Angeles-class submarine, is the third ship of the United States Navy to be named for San Francisco, California. ...

See also

• Guyot

A guyot is a flat-topped seamount. ...

References

1. ^ Nybakken, James W. and Bertness, Mark D., 2005. Marine Biology: An Ecological Approach. Sixth Edition. Benjamin Cummings, San Francisco
2. ^ Boehlert, G. W. and Genin, A. 1987. A review of the effects of seamounts on biological processes. 319-334. Seamount, islands and atolls. Geophysical Monograph 43, edited by B. H. Keating, P. Fryer, R. Batiza, and G. W. Boehlert.
3. ^ Rogers, A. D. 1994. The biology of seamounts. Advances in Marine Biology 30:305-350

Notes

• Keating, B.H., Fryer, P., Batiza, R., Boehlert, G.W. (Eds.), 1987: Seamounts, islands and atolls. Geophys. Monogr. 43:319-334.
• Koslow, J.A. (1997). Seamounts and the ecology of deep-sea fisheries. Am. Sci. 85:168-176.
• Menard, H.W. (1964). Marine Geology of the Pacific. International Series in the Earth Sciences. McGraw-Hill, New York, 271 pp.

External links

• SeamountsOnline, a database of seamount biology
• Volcanic History of Seamounts in the Gulf of Alaska
• Hydrographic structure and circulation at the Great Meteor Seamount showing an example of an isolated seamount and the formation of a submerged island of life.
• Seamount Oasis
• CenSeam, Census of Marine Life project CenSeam: a global census of marine life on seamounts
• Vulnerability of deep sea corals to fishing on seamounts beyond areas of national jurisdiction Report authored by Clark et al. (2006)