Seamounts can be found in every ocean basin in the world, distributed extremely widely both in space and in age. A seamount is technically defined as an isolated rise in elevation of or more from the surrounding seafloor, and with a limited summit area, of conical form. There are more than 14,500 seamounts. In addition to seamounts, there are more than 80,000 small knolls, ridges and hills less than 1,000 m in height in the world's oceans. Most seamounts are volcanic in origin, and thus tend to be found on oceanic crust near mid-ocean ridges, mantle plumes, and island arcs.
Geography
Seamount
Seamount | Geography
Seamounts can be found in every ocean basin in the world, distributed extremely widely both in space and in age. A seamount is technically defined as an isolated rise in elevation of or more from the surrounding seafloor, and with a limited summit area, of conical form. Most they are volcanic in origin, and thus tend to be found on oceanic crust near mid-ocean ridges, mantle plumes, and island arcs Most seamounts are volcanic in origin, and thus tend to be found on oceanic crust near mid-ocean ridges, mantle plumes, and island arcs. Most seamounts are volcanic in origin, and thus tend to be found on oceanic crust near mid-ocean ridges, mantle plumes, and island arcs.
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The ridges contain individual volcanoes and reach lengths of over ; in the Italian and Bach Ridges the volcanoes are high. The Musicians horst and the Southern Ridges are additional features of the Musicians Seamounts. Terrain observed by remotely operated vehicles shows large blocks, pillow lavas, flat terrain, lava flows and talus. The total number of seamounts is about 65, some of which Henry William Menard named after 18th century musicians. Among the seamounts known by name are:
Musicians Seamounts | Geography and geomorphology
The seamount lies in the Mid-Pacific Mountains on their southern side and is a submarine mountain with a flat top that rises over to a depth of -. The flat top has an oval shape and a surface area of ; it is characterized by a limestone dome on the summit, buried beneath sediments; in turn a volcanic hill is buried within the limestone dome. The top of the seamount has a hummocky appearance which has been interpreted as a sediment cover and its southeastern sector has a bank-like shape that resembles that of an atoll. Cape Johnson Guyot is considered to be of Middle Cretaceous age with an age of 120 million years reported and shallow-water fossils were emplaced on it at that time.
Cape Johnson Guyot | Geography and geology
A seamount is a large geologic landform that rises from the ocean floor but 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 abruptly and are usually found rising from the seafloor to in height. They are defined by oceanographers as independent features that rise to at least above the seafloor, characteristically of conical form. The peaks are often found hundreds to thousands of meters below the surface, and are therefore considered to be within the deep sea. During their evolution over geologic time, the largest seamounts may reach the sea surface where wave action erodes the summit to form a flat surface.
Seamount | Introduction
While the official name for these features refers to knolls, researchers in different disciplines see these features in different terms. These features are often referred to as seamounts where a seamount is described as any geographic isolated topographic feature on the seafloor taller than , including ones whose summit regions may temporarily emerge above sea level, but not including features that are located on continental shelves or that are part of other major landmasses. The seamounts are the site of volcanism from the late Cenozoic era. The knolls are high, stand deep at their base and at their summit. Many of the seamounts bear marks of tidal scour from water erosion, the result of millions of years of wear by a current moving at per second.
Graveyard Seamounts | Geography and geology
Numerous craters and small volcanic cones dot its flanks which bear evidence of sector collapses.
Cadamosto Seamount | Geography and geomorphology
The seamount is elongated in about northeast-south-southwest direction, with ridges radiating from its northern sector and the lower southern sector spreading southwestward like a tongue. This elongation matches the trend of magnetic lineations on the surrounding seafloor, implying that it may be controlled by the surrounding tectonic environment. The submarine slopes of the seamount are quite steep and show two benches at and depth. The seamount has dimensions of on the seafloor. About 15–20 parasitic vents dot the deeper flanks of the seamount and reach height, and small ridges en echelon to Vesteris are found on the southeastern flank. The total volume of the seamount is about .
Vesteris Seamount | Geography and geology
The shallowest part of the chain is on one of the western seamounts and lies at depth while Sasha reaches to , "MIB" to depth, "MOK" to and "NEW" to ; in general the seamounts shallow westward and their outline changes from conical to more elongated.
Lamont seamount chain | Geography and geomorphology
Seamounts can be found in every ocean basin in the world, distributed extremely widely both in space and in age. A seamount is technically defined as an isolated rise in elevation of or more from the surrounding seafloor, and with a limited summit area, of conical form. There are more than 14,500 seamounts. In addition to seamounts, there are more than 80,000 small knolls, ridges and hills less than 1,000 m in height in the world's oceans. Most seamounts are volcanic in origin, and thus tend to be found on oceanic crust near mid-ocean ridges, mantle plumes, and island arcs.
Seamount | Geography
A number of flat-topped seamounts rise from the floor of the western Pacific Ocean to depths of below sea level. They are called guyots and are clustered in an elongated region with and between the Marshall Islands and the Tuamotus. It is presumed that hotspots generated most of these seamounts. The Marshall Islands are grouped in two chains and three groups, the Ratak Chain including Limalok Guyot, the Ralik Chain including Wōdejebato Guyot and an isolated cluster farther west including Eniwetok Island.
Ruwitūn̄tūn̄ | Geological context
It might have formed either through erosion of surrounding sediments by ocean currents or through isostatic subsidence.
Anton Dohrn Seamount | Geography and geomorphology
Seamount – A mountain rising from the ocean seafloor that does not reach to the water's surface
Outline of oceanography | Seamounts
Only Bilbo Seamount and Vayda Seamount show clear evidence of once having been emerged islands.
Researcher Ridge | Geography and geomorphology
Otherwise, seamounts tend not to form distinctive chains in the Indian and Southern Oceans, but rather their distribution appears to be more or less random. Isolated seamounts and those without clear volcanic origins are less common; examples include Bollons Seamount, Eratosthenes Seamount, Axial Seamount and Gorringe Ridge.
Seamount | Grouping
In addition there are long gullies formed either by erosional or volcanic processes, as well as parasitic vents and volcanic ridges.
Tropic Seamount | Local
The Foundation chain eventually becomes a set of three ridges close to the Pacific-Antarctic Ridge, the northern two of which are the more voluminous ones. These northern ridges are probably the main ones; the southern one may have formed through cracks in the crust induced by the northern ridge, but it might also be a "paired" expression of a hotspot similar to the Kea and Loa trends in Hawaii. The seamounts reach depths of beneath sea level (the highest seamount is located at ), and contain typical volcanic features such as smaller volcanic cones, calderas and individual rift zones. Some of the seamounts close to the ridge have flat tops and show evidence of having formed islands above sea level in the past.
Foundation Seamounts | Geography
The seamounts in the field are typically less than wide but several kilometres wide; seamounts that are part of a ridge are between high. The total volume of rocks in the seamount province is about .
Rano Rahi seamounts | Geography and geomorphology
They are formed from mud volcanism. The composition for the seamounts differ in the Izu-Ogasawara Trench and Mariana systems which indicates regional changes in geology.
Mariana Plate | Defining Features
On its northern and northeastern side, this ridge is in turn surrounded by another wide slightly raised ridge. The flat top has been interpreted as a lagoon surrounded by reefs which form the inner ridge; the outer ridge appears to be a pile of skeletal sand rather than a reef and may be a spit formed by reworked material. Small mounds, probably of biological origin, are found at the margins of the seamount. The seamount is high above the sea floor and has an irregular shape, with spurs projecting from its circumference. These spurs have widths of and surface features that are distinct from those on the main flat top.
Wōdejebato | Local setting
The Western Pacific Ocean features many seamounts with flat tops at depths of below sea level which are known as guyots. They were considered to be remnants of eroded islands before Cretaceous carbonate platforms were discovered on them which resemble present-day atolls although they do not have exactly the same properties. Later similar submarine mountains were identified elsewhere in the Pacific Ocean as well. Menard 1958 suggested that the Western Pacific guyots once were part of an elevated region known as the Darwin Rise, later compared to present day French Polynesia. Many of these seamounts originally formed in the South Pacific, such as in French Polynesia, where a number of recent volcanoes and volcanic chains can be found.
Takuyo-Daisan | Regional
The region lies between and around the islands of Pitcairn and Easter Island. There, the East Pacific Rise is interrupted by a trapezoid microplate known as the Easter Microplate about wide. Seafloor spreading occurs at a rate of about . There is a topographic swell that connects the two islands and continues eastward towards Sala y Gomez. The origin of this swell and the various volcanoes and seamounts associated with it has been variously explained as either being due to a mantle plume which forms volcanoes that are then carried away through plate motion or by a "hot line" where a number of simultaneously active volcanic centres develop.
Crough Seamount | Regional
This is a list of Seamounts in the Southern Ocean. 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, islet or Cliff-rock. Seamounts are typically formed from extinct volcanoes that rise abruptly and are usually found rising from the seafloor to in height. They are defined by oceanographers as independent features that rise to at least above the seafloor, characteristically of conical form.
List of seamounts in the Southern Ocean | Introduction
A conspicuous feature of the chain, as of the adjacent tableland, is the number of its parameras, isolated plateaus shut in by lofty mountains or even by precipitous walls of rock.
Cantabrian Mountains | Geography
Henry Seamount is located southeast of El Hierro, an island in the Canary Islands. It rises above the Jurassic ocean floor at depth, forming a dome. The seamount features ridges and gullies and a sharp slope break with respect to the surrounding ocean floor. The seafloor on the seamount itself is covered by sediments and pelagic ooze containing foraminifera and nanofossils has been found on the summit. Underwater cameras have observed deposits of lapilli and volcanic ash, outcrops of basement on Henry Seamount and pale sediment, while clam shells are widespread in the summit region. The surrounding ocean floor is covered with mounds and with various linear shapes and there is another volcanic seamount south of Henry Seamount while a moat north of the seamount may be a product of bottom scouring by ocean currents.
Henry Seamount | Geography and geomorphology
Its characteristics include coastal cliffs and rocky shores.
Qaqulluit | Geography
Other points on the Plateau also rise to depths of less than . The plateau appears to be a wave-cut platform of Pleistocene age, when sea levels were lower, and is swept by strong ocean currents. The seamount rises from a depth of , where it occupies a breadth of and forms an isolated conical feature. The seafloor from which Vema rises belongs to the abyssal plain of the Cape Basin. From there, the slopes of Vema first rise steeply and feature subsidiary summits; above depth the slopes flatten.
Vema Seamount | Geomorphology and geography
A thick layer of sediment covers the flat top and appears to be reworked by storms and sea currents. Mounds, slope breaks and other volcanic pinnacles are located on the flat top. The seamount tilts southeastward. Beyond the margin of the flat top, the slopes of Anton Dohrn Seamount drop down to depth. The steep slopes have been variously described as either lacking a sediment cover or featuring gravelly sediments along with outcropping bedrock. There are cliffs, ridges and rockfalls but no gullies or canyons. Parasitic cones lie on the northwestern slope. A moat surrounds the seamount and reaches depths of about .
Anton Dohrn Seamount | Geography and geomorphology
The most important feature of the hydrodynamics of the Condor seamount is the presence of a mainstream coming from North, and a pattern of movement with rotation to the right (clockwise) over its Western Ridge. This pattern of movement can capture and retain nutrients and organisms from the outside of the Bank, in the area of 50–60 m above its top. This model can be interrupted by sporadic events of default elimination of movement, which can last up to a few months, encouraging the entry of new materials of the surrounding areas. Thus, the biological productivity of the area may change depending on oceanographic conditions.
Condor seamount | Oceanography
The Discovery Seamounts are a group of seamounts east of Gough Island and southwest from Cape Town which extend over an east-west region of over length. The seamounts rise over to depths of and have the shape of guyots; this implies that they formerly rose above sea level, guyots form when islands are eroded to a flat plateau that is then submerged through thermal subsidence of the lithosphere. The shallowest peak reached by a seamount from the group is a depth of , although a depth of has been reported for Discovery Seamount also. These seamounts are also referred to as the Discovery Rise and subdivided into a northwestern and a southeastern trend.
Discovery Seamounts | Geography and geomorphology
Given its height, during the last glacial maximum Adams was likely an island. Its slopes are covered by recent lava flows, volcanic debris and hyaloclastite. Lava flows feature aa lava characteristics and lava tubes, while deeper parts of the edifice are covered with lapilli and scoria. Parasitic vents form cones and mounds on its flanks.
Adams Seamount | Geography and geomorphology
All the seamounts in the group are complex northeast-southwest trending structures, consisting of parallel ridges separated by sediment-filled troughs. The ridges constructed run parallel to an ancient spreading center which has since been replaced in its role by the San Andreas Fault system. They are unique in this origin, as they are formed from the remnants of an old ocean-ridge spreading center. A series of "knobs" are aligned with the ridges; however the distinctive summit crater, evident in many oceanic volcanoes, is absent. This lack of a collapse crater suggests that magma was never stored in a chamber within the structure, as with most other volcanoes.
Davidson Seamount | Geology
The seamount is located in the Greenland Sea-Norwegian Sea, west of due north from Jan Mayen Island and in between Norway and Greenland. Vesteris Seamount is an isolated volcanic seamount that reaches a depth of below sea level and with two summits that rise from a plateau at depth; it is likely that the summit once emerged from the sea. The summit area of the seamount is flat, probably due to wave erosion during the Weichselian glaciation, and sediment cover is scarce. Lava flows extend from the summit area to depths of almost , and sheet flows, scarps, pillow lavas, lava tubes and lava debris have been observed on the seamount.
Vesteris Seamount | Geography and geology
A mid-ocean ridge is a general term for an underwater mountain system that consists of various mountain ranges (chains), typically having a valley known as a rift running along its spine, formed by plate tectonics. This type of oceanic ridge is characteristic of what is known as an oceanic spreading center, which is responsible for seafloor spreading.
List of submarine topographical features | Mid-ocean ridges
This field lies west of the East Pacific Rise, and covers an area between the Rise and 118° western longitude and between 17° and 19° southern latitude. The Pukapuka submarine ridge extends west of the field towards the Tuamotu islands. The Rano Rahi seamount field consists of several chains of seamounts which emanate from the East Pacific Rise. These chains are lined up in the direction of the motion of the Pacific Plate and the farther away from the East Pacific Ridge the more the seamounts overlap with each other until they form ridges, which reach median lengths of .
Rano Rahi seamounts | Geography and geomorphology
Geographical features include:
Molar Massif | Features
Tropic Seamount lies in the northeast Atlantic Ocean west of Cape Blanc and south of the Canary Islands off the coast of Mauretania, Northwestern Africa. The seamount is currently claimed as part of the EEZ of Spain, as of 2017 Morocco also laid an EEZ claim over the area.
Tropic Seamount | Geography and geomorphology
The New England Seamounts is a chain of over twenty underwater extinct volcanic mountains known as seamounts. This chain is located off the coast of Massachusetts in the Atlantic Ocean and extends over 1,000 km from the edge of Georges Bank. Many of the peaks of these mountains rise over 4,000 m from the seabed. The New England Seamounts chain is the longest such chain in the North Atlantic and is home to a diverse range of deep sea fauna. Scientists have visited the chain on various occasions to survey the geologic makeup and biota of the region. The chain is part of the Great Meteor hotspot track and was formed by the movement of the North American Plate over the New England hotspot.
New England Seamounts | Introduction
Researcher Ridge lies in the Atlantic Ocean on the western side of the Mid-Atlantic Ridge, just south of the Fifteen-Twenty Fracture Zone. The Mid-Atlantic Ridge lies about east of Researcher Ridge. The ridge is a chain of individual seamounts. It is about long with an east-southeast-to-west-northwest strike and its minimum depth decreases eastward to , concordant with mean water depth. The individual seamounts that make up the ridge are, from east to west, Gollum Seamount, Vayda Seamount, Bilbo Seamount, Gandalf Seamount, The Shire Seamount, Pippin Seamount, Merry Seamount, Molodezhnaya Seamount, Frodo Seamount, Sam Seamount, and Mount Doom Seamount. Small cones occur on the surface of Vayda Seamount, which rises to a depth of about below sea level; many of these seamounts appear to be guyots.
Researcher Ridge | Geography and geomorphology
Krylov Seamount lies west of the Cape Verde islands in the Cape Verde Basin of the East Atlantic, at a water depth of ; the highest point lies at and the seamount rises about above the seafloor. It is an elongated volcano that consists of an eastern summit at about depth ("Krylov Seamount" proper), separated from a western ridge ("Krylov Ridge") by a wide depression. Formerly, the whole seamount was interpreted to be an apparently volcanic breccia-filled summit caldera plus three separate summits sharing a common pedestal at depth. The terrain of the seamount is covered by organic debris, which with depth gives way to pillow lavas; marine sediments cover much of the outer slopes of the seamount.
Krylov Seamount | Geography and geomorphology
This deep depression may be a volcanic crater but the more likely explanation is that the rim was formed by living organisms. The whole summit plateau covers an area of and the total volume of the seamount is about . Dredging has yielded no volcanic material, but chert, limestones (in the form of grainstone, packstone and wackestone) encrusted with ferromanganese as well as living animals were pulled up. The seafloor underneath the guyot lies at a depth of and has an age of 157 million years.
Darwin Guyot | Geography and geomorphology
Cadamosto Seamount lies about southwest of the island of Brava in the Cape Verde islands. Its name refers to Alvise Cadamosto, who discovered the Cape Verde islands in 1456. The seamount is wide at its foot and partially overlaps with Brava. Cadamosto and Brava may be part of a larger northeast-southwest trending alignment of volcanoes. It rises from a depth of to about depth and has a summit with three separate, well-preserved volcanic centres. Sediment cover is sparse and there is evidence of hydrothermal alteration and of recent activity in the form of spatter deposits. Agglutinates and lavas form most of the seamount.
Cadamosto Seamount | Geography and geomorphology
Channels, debris flow fronts and levees decorate its slopes. Noticeable ridges emanate from the east-southeastern, southwestern, west-northwestern and north-northeastern corners of the seamount; they appear to be rift zones, and flank cones are found on the eastern slopes. The southern slopes feature slump deposits, and the entire seamount is surrounded by a sediment fan. The volume of the entire seamount is about . Two large seamounts lie west and southwest of Takuyo-Daisan with a smaller seamount between the two; Takuyo-Daini is the western one and Jensen seamount the south-western one. The seafloor underneath Takuyo-Daisan has an age of 143 million years.
Takuyo-Daisan | Local
After a period of explosive activity near the ocean surface, the eruptions slowly die away. With eruptions becoming infrequent and the seamount losing its ability to maintain itself, the volcano starts to erode. After finally becoming extinct (possibly after a brief rejuvenated period), they are ground back down by the waves. Seamounts are built in a far more dynamic oceanic setting than their land counterparts, resulting in horizontal subsidence as the seamount moves with the tectonic plate towards a subduction zone. Here it is subducted under the plate margin and ultimately destroyed, but it may leave evidence of its passage by carving an indentation into the opposing wall of the subduction trench.
Seamount | Geochemistry and evolution
The Lamont seamount chain is a group of five seamounts in the Pacific Ocean; from southeast to northwest they are known as "Sasha", "MIB", "MOK", "DTD" and "NEW" and there is an additional unnamed seamount southwest from "NEW". The seamounts were discovered in 1983 and named later. The seamounts reach heights of and have summit craters/calderas, that on "DTD", "MOK" and "NEW" form nested, complex calderas. Horseshoe-shaped volcanic ridges accompany the calderas and lava effusion appears to have preferentially occurred on the margins of the calderas, along with mass wasting. The Lamont seamount chain forms a long chain and the individual seamounts surrounded by lava cones high.
Lamont seamount chain | Geography and geomorphology
Takuyo-Daisan is a guyot that rises to a minimum depth of and is capped by an approximately square-shaped surface platform at about depth which has a surface area of about . Depressions up to deep cover the flat top. The top is surrounded by a wide and up to high ridge, especially on the northeastern and southern sides. It may be either a bioherm or a karst landform. A - high structure may be part of the old volcanic edifice; the interface between the carbonate platform and the volcanic basement has a sloping aspect. Away from the platform, the seamount has steep slopes probably formed by short lava flows that rise above the seafloor.
Takuyo-Daisan | Local
Natural geographic feature – an ecosystem or natural landform.
Outline of geography | Natural geographic features
Geographical features include:
Quarles Range | Features
The geologic history of Lo-En seamount is relatively poorly known; paleomagnetic data have been used to infer an age of 45–85 million years ago for the seamount. It was located at about 25–30 degrees southern latitude when it formed, south of the hotspots that are presently active in the Cook Islands–Austral Islands. Eniwetok is about 36 million years younger than Lo-En.
Lo-En | Geologic history
The Pacific Ocean is characterized by long island chains, which typically extend from the southeast to the northwest in direction of the motion of the Pacific Plate. Often, such chains begin in the southeast with volcanoes such as Hawaii that become progressively more eroded northwestward and eventually end as series of atolls. This has led to the suggestion that they are formed by deep sources over which the Pacific Plate drifts and eventually carries the volcano away from its magma source. These sources are known as "hotspots", and their total number has been estimated to be between 42 and 117.
Macdonald seamount | Regional setting
Geographical features include:
Anderson Massif | See also
Tropic Seamount is the southernmost member of the Canary Islands Seamount Province (CISP), which reaches from north of Lanzarote in the Canary Islands to southwest of the archipelago and contains over a hundred seamounts in a space long. This province aside from Tropic Seamount in the south includes The Paps Seamount, Ico Seamount, Echo Bank and Drago Seamount but also Essaouira Seamount north of Lanzarote. Especially the southern among these underwater mountains are poorly studied. Aside from the seamounts, submarine canyons and large debris flows occur in the region such as the Sahara Slide which has run around Echo Bank.
Tropic Seamount | Regional
The Musicians Seamounts lie in the north-central Pacific, north of the Hawaiian Ridge north and northwest of Necker Island, extending over a length of . The seamounts were formerly known as the North Hawaiian Seamount Range and were among the first submarine mountains to be thoroughly researched. The seamounts consist of two separate chains (one trending in north-south direction parallel to the Emperor Seamounts and the other in northwest-southeast direction parallel to the northern Line Islands) of ridges that extend east-west and seamounts. Seamounts have usually an elliptical cross section and heights of and no flat tops like other seamounts south of the Hawaiian Ridge; the highest is Liszt Seamount whose summit has a depth of .
Musicians Seamounts | Geography and geomorphology
Geographical features include:
Herbert Mountains | Features
The seamount is the location of a positive gravity anomaly that is thought to indicate the presence of a thick igneous body.
Hebrides Terrace Seamount | Geography and geomorphology
Anton Dohrn Seamount is located in the northeast Atlantic Ocean west of Scotland, approximately halfway between St Kilda (Hebrides) and Rockall, about west of the former. It lies in the Rockall Trough, an over deep submarine depression of unclear origin. North-northeast lies the Rosemary Bank and Hebrides Terrace Seamount is found south-southeast from the seamount. The seamount is located inside the exclusive economic zone of the United Kingdom. Anton Dohrn Seamount is a high and about wide circular guyot with a flat top at depth. Flat-topped seamounts are unusual in the North Atlantic. The shallowest point of the seamount lies at about depth and is formed by a pinnacle that protrudes from the deep summit platform.
Anton Dohrn Seamount | Geography and geomorphology
The Pacific Ocean seafloor, especially the Mesozoic seafloor, contains most of the world's guyots (also known as tablemounts). These are submarine mountains which are characterized by steep slopes, a flat top and usually the presence of corals and carbonate platforms. While there are some differences to present-day reef systems, many of these seamounts were formerly atolls. Some atolls still exist, for example at Pikinni. All these structures originally formed as volcanoes in the Mesozoic ocean. Fringing reefs may have developed on the volcanoes, which then became barrier reefs as the volcano subsided and turned into an atoll. The crust underneath these seamounts tends to subside as it cools, and thus the islands and seamounts sink.
Wōdejebato | Regional setting
The Foundation Seamounts form a long and wide band of seamounts that extend northwestward away from the Pacific-Antarctic Ridge towards the Resolution () and Del Cano () fracture zones. A small ridge continues from there to the Macdonald seamount, but the relation of this ridge to the Foundation Seamounts appears to be questionable at best, and there are no other clear bathymetric features in between Foundation and Macdonald. Close to the western end of the Foundation Seamounts lie the "Old Pacific Seamounts", which may have the same origin. On the other end of the chain, the seamounts become short ridges decorated by volcanic cones; the Pacific-Antarctic Ridge is migrating northwestward and approaching the hotspot, and the younger crust close to the ridge results in the morphology of developing volcanoes being altered.
Foundation Seamounts | Geography
Four natural regions can be distinguished in the entity: the coastal mountain range, the depression of Lake Valencia, the inland mountain range, and the Central Wavy Plains. In the depression of Lake Valencia, recent sedimentary formations predominate, while the mountainous areas present others that are highly affected by metamorphic processes, although in the presence of nuclei with more conserved igneous and sedimentary rocks. In the mountain ranges of the Interior chain, galleys can be observed, as spurs of that mountain range, which smoothen their forms towards the South until they enter the formation of the plains.
Aragua | Geology
Resolution Guyot is part of the western Mid-Pacific Mountains, located west of Hawaii, north-northeast of the Marshall Islands. Unlike conventional Pacific Ocean island chains, the Mid-Pacific Mountains are a group of oceanic plateaus with guyots (also known as tablemounts)) that become progressively younger towards the east. Other guyots in the Mid-Pacific Mountains are Sio South, Darwin, Thomas, Heezen, Allen, Caprina, Jacqueline and Allison. The seamount is about high and rises from a raised seafloor to a depth of about . At a depth of it is capped off by a wide rather flat and roughly circular summit platform with a high rim and a moat inside of this rim.
Resolution Guyot | Local setting
In the middle of the chain lies Mount Steere with a summit elevation of and a rectangular summit caldera. Lie Cliff is a volcanic outcrop on the northeastern flank. Mount Steere is heavily dissected, bears evidence of former glaciation in the form of moraines and cirques have been eroded into its northern and northeastern flanks. As with Mount Rees, volcanic rocks alternate between these that formed subglacially and these formed subaerially. Outcrops feature breccias and lava with numerous intruded dikes.
Crary Mountains | Geography and geomorphology
The large guyot rises over from the eastern flank of the Tonga Trench to a depth of . It features a wide flat top at depth, which tilts gently westwards. A north-northeast trending scarp separates the flat top from another, shallower flat-topped knoll on the eastern side of the flat top which also tilts westwards; the shallowest point of the seamount lies on this knoll. Additional volcanic cones dot the slopes of Capricorn Seamount. At its foot the seamount is wide. The crust underneath the seamount is 75-95 million years old and is thickened, perhaps by the seamount's lava flows.
Capricorn Seamount | Geomorphology and geology
The shallowest point lies at a depth of about . It consists of nine volcanic cones that overlie a sedimentary structural high; the cones and the structural high make up the seamount. The wide 'Vince volcano' is the largest volcanic cone and forms a solitary northeasterly summit; the other eight are clustered in the southwest and one of these forms the shallowest point of the seamount. The southern slopes are steep and feature canyon-like features, the northern slopes are more gentle. Two faults, the North Coral Patch Ridge fault and the South Coral Patch Ridge fault, run northeastward away from Coral Patch Seamount.
Coral Patch Seamount | Geography and geomorphology
The seamount lies in the southern Rockall Trough, at the foot of the Scottish continental slope and west-southwest of Barra Head, Hebrides. It is the smallest of three seamounts in the Rockall Trough; the other two are Anton Dohrn Seamount and Rosemary Bank both north of Hebrides Terrace Seamount, and farther west is the Rockall Bank. It straddles the political border between the United Kingdom and Ireland. The Hebrides Terrace Seamount is a volcanic guyot, a seamount with a flat top and steep slopes, that rises to a depth of about . It is about wide at its basis and its southern and western flanks feature canyons, escarpments and gullies.
Hebrides Terrace Seamount | Geography and geomorphology
The isolated seamount lies about halfway between the Canary Islands and Cape Verde, west of West Sahara/Mauritania and on the upper continental rise. It is a wide guyot with the shape described as a diamond or of a square and a summit area with a four-point star form. The seafloor around Tropic Seamount has an age of about 155-150 million years and is covered by Quaternary silt, pelagic ooze and aeolian sediments; there is no indication of other volcanic edifices in the neighbourhood or of a swell although the so-called San Borondón crest connects it to Echo Bank. The seamount rises from a depth of to a depth of and a diamond-shaped flat summit that has a surface area of about and is covered with pelagic ooze and sediments; the shallowest sector of the seamount lies at depth.
Tropic Seamount | Local
A further sampling cruise by the United States Geological Survey (USGS) recovered pillow lava and hyaloclastite from 4 of the 8 volcanoes. The samples seemed to be of more primitive origin then those erupted elsewhere on the ridge. In 1998, the Monterey Bay Aquarium Research Institute conducted two dives on a cone cluster located southeast of the main structure. The chain consists of eight volcanoes. Of these, four are self-dependent, whereas the other four form twin fused, morphalogically complex, flat-topped structures. The volcanoes form a linear chain, and are relatively small, measuring less than in diameter, and are nearly circular in shape.
President Jackson Seamounts | Introduction
Geographical features include:
Athos Range | Features
On the other end of the ridge, "Buffon" seamount rises to a depth of and likewise shows evidence of having emerged above sea level, as well as of extensive erosion. The seamounts were originally named after letters of the alphabet A-Z followed by Aa-Hh; later they were numbered through from west to east and names based on scientists such as Ampere proposed.
Foundation Seamounts | Geography
Geographical features include:
Bush Mountains | Features
Possibly, as such a seamount or a seamount chain subducted it indented the trenches, forming a re-entrant.
Erimo Seamount | Regional
This flat summit is covered by high volcanic cones and features terraces at the margin of the summit as well as ridges that point due north, east, south and west. Volcanic cones are concentrated in the southern and eastern parts of the summit platform. The seamount has a volume of about , similar to other Atlantic Ocean volcanoes. Raised beaches have been reported from Tropic Seamount. The outer slopes of the seamount become steeper to the summit perhaps due to geochemical differences between the rocks that form the lower slopes and these of the upper slopes. They are cut by curved flank collapses that open to the northeast, southeast, southwest and northwest; these collapses have cut into the volcanic edifice and have left ridges between the individual collapses which give the seamount its four-point star form and deposited debris around the seamount, although the deposits are not recognizable probably because they are old and buried beneath sediments.
Tropic Seamount | Local
Overall, seamount and guyot coverage is greatest as a proportion of seafloor area in the North Pacific Ocean, equal to 4.39% of that ocean region. The Arctic Ocean has only 16 seamounts and no guyots, and the Mediterranean and Black seas together have only 23 seamounts and 2 guyots. The 9,951 seamounts, which have been mapped, cover an area of . Seamounts have an average area of , with the smallest seamounts found in the Arctic Ocean and the Mediterranean and Black Seas, whilst the largest mean seamount size occurs in the Indian Ocean . The largest seamount has an area of and it occurs in the North Pacific.
Seamount | Geography
Though the remaining ridge appears to be a steep and weathered fault scarp evidence suggests the geographic features are from wind and water rather than the landslide event. The volcano collapsed nearly in half at the caldera with the eastern half falling into the ocean cataclysmically with enough force to send debris including the massive Tuscaloosa seamount across the ocean floor and up a ridge. This landslide created a massive tsunami which ravaged the islands and possibly the Western coast of ancient North America.
Nuʻuanu Slide | Introduction
Vema Seamount lies in the South Atlantic Ocean, away from Tristan da Cunha. The cities of Cape Town and Lüderitz lie east-southeast and northeast of Vema, respectively, with Cape Town about distant. The seamount has a conical shape with a flat top; the shallowest point rises to an elevation of below sea level and is called Collins Point. At least one source gives a minimum depth of for the seamount, while recent bathymetric surveys have found a minimum depth of . The flat top is a summit plateau has a width of and as more recently determined at a mean depth of and has been named Emerson Plateau; it has a vaguely triangular shape pointing west, and Collins Point lies close to the western margin of the Emerson Plateau.
Vema Seamount | Geomorphology and geography
These tops must be or more below the surface of the sea; the diameters of these flat summits can be over . Knolls are isolated elevation spikes measuring less than . Lastly, pinnacles are small pillar-like seamounts.
Seamount | Structure
Geographic features are features of the Earth, natural or not. Natural geographical features consist of landforms and ecosystems. For example, terrain types (physical factors of the environment) are natural geographical features. Conversely, human settlements or other engineered forms are considered types of artificial geographical features.
Geographical feature | Introduction
Guyots cover a total area of and have an average area of , more than twice the average size of seamounts. Nearly 50% of guyot area and 42% of the number of guyots occur in the North Pacific Ocean, covering . The largest three guyots are all in the North Pacific: the Kuko Guyot (estimated ), Suiko Guyot (estimated ) and the Pallada Guyot (estimated ).
Seamount | Geography
Seamounts are underwater mountains that rise from the depths of the ocean, and whose summits can sometimes be found just a few hundred metres below the sea surface. To be classified as a seamount the summit must be 1000 m higher than the surrounding seafloor, and under this definition there are an estimated 1000–2800 seamounts in the Atlantic Ocean and around 60 in the Mediterranean Sea. Seamounts enhance water flow through localised tides, eddies, and upwelling, and these physical processes may enhance primary production. Seamounts may therefore be considered as hotspots of marine life; fauna benefit from the enhanced hydrodynamics and phytoplankton supply, and thrive on the slopes and summits.
Hotspot Ecosystem Research and Man's Impact On European Seas | Seamounts
Geographic features, northwest to southeast, include:
Temescal Mountains | Geographic features
Compared to mid-ocean ridge seamounts, subduction zone seamounts generally have more sodium, alkali, and volatile abundances, and less magnesium, resulting in more explosive, viscous eruptions. All volcanic seamounts follow a particular pattern of growth, activity, subsidence and eventual extinction. The first stage of a seamount's evolution is its early activity, building its flanks and core up from the sea floor. This is followed by a period of intense volcanism, during which the new volcano erupts almost all (e.g. 98%) of its total magmatic volume. The seamount may even grow above sea level to become an oceanic island (for example, the 2009 eruption of Hunga Tonga).
Seamount | Geochemistry and evolution
The Condor Seamount is located in the following geographic coordinates: latitude - 38°24′–38°38′N, longitude: 29°16′–28°51′W, having a surface area of 447 km2. On the west ridge, the shallowest zone of the Bank, the occurrence of rounded rocks indicate that this area was exposed to surface waves, when the sea level was about 120 m below current levels.
Condor seamount | Location
Strabo refers to his "Geography" within it by several names: Apart from the "outline", two words recur, "earth" and "country." Something of a theorist, Strabo explains what he means by Geography and Chorography:It is the sea more than anything else that defines the contours of the land ("geōgraphei") and gives it its shape, by forming gulfs, deep seas, straits and likewise isthmuses, peninsulas, and promontories; but both the rivers and the mountains assist the seas herein. It is through such natural features that we gain a clear conception of continents, nations, favourable positions of cities and all the other diversified details with which our geographical map ("chorographikos pinax") is filled.
Geographica | Title of the work
Some of these vents form alignments and Ioah lies at the intersection of two strike-slip faults. The seamount rises from the East Mariana Basin over Jurassic seafloor, between the two Ogasawara Fracture Zones.
Ioah Guyot | Geography and geomorphology
The Pacific Ocean contains several long seamount chains, formed by hotspot volcanism. These include the Hawaiian–Emperor seamount chain, the Tasmantid Seamount Chain, the Lord Howe Seamount Chain and the Louisville Ridge.
Geology of the Pacific Ocean | Seamount chains and hotspots
Geographical features include:
Holyoake Range | Features
The low Atlantic coast and the hilly or mountainous Pacific coast foreshadow the leading features in the distribution of mountains within the United States.
Geography of the United States | Physiographic regions
The seamount was named for the 58th emperor of Japan, Emperor Koko (A.D. 885-887) by geologist Thomas Davies and his colleagues in 1972, based on the results from a bathymetric expedition and contents of two dredge huals, led by Thomas Washington and undertaken with the ship "Aries-7". The seamount is elongate in shape, aligned northwest-southeast (the same direction as the chain), and has a gentle slope and a large, flat top. Koko Seamount also has a lot of small reefal bodies on its slopes. It rises from the abyssal floor about in height. A prominent south-trending ridge extends about from the summit area in the direction of Kimmei Seamount, to the southeast.
Koko Guyot | Geology and characteristics
The seamount is very close to the "V"-shaped bend in the Hawaiian-Emperor seamount chain, and thus would be useful in understanding the exact age of the bend. Although few dredge samples are available, they have all been reliably dated at 47 million years (Sharp and Clague, Science, 313, 1281-84, 2006), during the Eocene epoch of the Paleogene period. During the cruise SO112 of the "R/V SONNE", high resolution bathymetric mapping was conducted, showing that Daikakuji is nearly in diameter and nearly in height, with a summit lying underwater. Because of its flat capped top, Daikakuji is considered a guyot. A smaller, younger, secondary guyot just east of the main mass overlaps its slope.
Daikakuji Guyot | Geology
Echo Bank rises from the continental slope to a depth of about below sea level, making it the shallowest seamount in the region. It has a maximally wide flat top like a guyot at a depth of that is surmounted by volcanic cones which reach depths of and also by small depressions; the cones cluster in the central summit platform. Around the summit lie terraces and scarps, with the terraces particularly pronounced on the eastern side and perhaps reflecting a slight tilt of the seamount. The slopes of the seamount are steep and cut by curved slide scars and gullies which both reach lengths of .
Echo Bank | Local
Observations show that both the north and south rift zones lack sediment cover, indicating recent activity. A bulge in the western part of the north rift zone contains three cone-shaped prominences.
Lōʻihi Seamount | Geology
The seamount is part of a group of seamounts about away from Pitcairn Island, which includes several small seamounts and the large Adams Seamount. These seamounts were discovered in 1989. Bounty has a conical shape, with three summit cones and several rift zones. Pillow lavas and hyaloclastite cover its slopes, and parasitic vents can be observed as well. The volcano has a volume of about and has a width of at its foot. Bounty has erupted rocks with compositions of alkali basalt, trachyandesite and trachyte.
Bounty Seamount | Geology and geomorphology
The Eratosthenes Seamount or Eratosthenes Tablemount is a seamount in the Eastern Mediterranean about 100 km south of western Cyprus. Unlike most seamounts, it is a carbonate platform not a volcano. It is a large, submerged massif, about 120 km long and 80 km wide. Its peak lies at the depth of 690 m and it rises 2000 m above the surrounding seafloor, which is located at the depth of up to 2,700 m and is a part of the Herodotus Abyssal Plain. It is one of the largest features on the Eastern Mediterranean seafloor. In 2010 and 2012 the Ocean Exploration Trust's vessel EV Nautilus explored the seamount looking for shipwrecks.
Eratosthenes Seamount | Introduction
Crough Seamount (named after the geologist Thomas Crough) is a seamount in the Pacific Ocean, within the exclusive economic zone of Pitcairn. It rises to a depth of and is paired with a taller but overall smaller seamount to the east. This seamount has a flat top and probably formed an island in the past. It is about 7-8 million years old, although a large earthquake recorded at its position in 1955 may indicate a recent eruption. The seamount appears to be part of a long geological lineament with the neighbouring Henderson and Ducie islands, as well as the southern Tuamotus and Line Islands.
Crough Seamount | Introduction
Geographical features of Gallipoli Heights include:
Gallipoli Heights | Features
Undersea mountain ranges are mountain ranges that are mostly or entirely underwater, and specifically under the surface of an ocean. If originated from current tectonic forces, they are often referred to as a "mid-ocean ridge". In contrast, if formed by past above-water volcanism, they are known as a "seamount chain". The largest and best known undersea mountain range is a mid-ocean ridge, the Mid-Atlantic Ridge. It has been observed that, "similar to those on land, the undersea mountain ranges are the loci of frequent volcanic and earthquake activity".
Undersea mountain range | Introduction
The geographical structure of South America is deceptively simple for a continent-sized landmass. The continent's topography is often likened to a huge bowl owing to its flat interior almost ringed by high mountains. With the exception of narrow coastal plains on the Pacific and Atlantic Oceans, there are three main topographic features: the Andes, a central lowland, and the extensive Brazilian and Guiana Highlands in the east. The Andes are a Cenozoic mountain range formed (and still forming) Altiplano and a number of major valleys such as the Rio Magdalena. These contain three of the world's highest capitals: Bogotá, Quito and highest of all, La Paz, Bolivia.
Geography of South America | Topography and geology
Gascoyne Seamount, also called Gascoyne Guyot or Gascoyne Tablemount, is a guyot in the Tasman Sea of the South Pacific Ocean. Located east of the Australian coastal town of Bermagui, Gascoyne Seamount is the southernmost and youngest seamount of the Tasmantid Seamount Chain. This is an underwater mountain range extending some to the north. The Tasmantid Seamount Chain has resulted from the Indo-Australian Plate moving northward over a stationary hotspot. The seamount is about 7 million years old. It incorporates a tropical to subtropical, very shallow water calcareous algal/encrusting foraminiferid biota, suggesting deposition in water deep. Age diagnostic forms have not been recovered.
Gascoyne Seamount | Introduction
A landform comprises a geomorphological unit and is largely defined by its surface form and location in the landscape, as part of the terrain, and as such is typically an element of topography. Landforms are categorized by features such as elevation, slope, orientation, stratification, rock exposure, and soil type. They include berms, mounds, hills, cliffs, valleys, rivers, and numerous other elements. Oceans and continents are the highest-order landforms. A body of water is any significant accumulation of water, usually covering the Earth. The term "body of water" most often refers to oceans, seas, and lakes, but it may also include smaller pools of water such as ponds, creeks or wetlands.
Geographical feature | Landforms
Geographical features include:
Herbert Range | Features
Seamounts can form in a wide variety of tectonic settings, resulting in a very diverse structural bank. Seamounts come in a wide variety of structural shapes, from conical to flat-topped to complexly shaped. Some are built very large and very low, such as Koko Guyot and Detroit Seamount; others are built more steeply, such as Loihi Seamount and Bowie Seamount. Some seamounts also have a carbonate or sediment cap. Many seamounts show signs of intrusive activity, which is likely to lead to inflation, steepening of volcanic slopes, and ultimately, flank collapse. There are also several sub-classes of seamounts. The first are guyots, seamounts with a flat top.
Seamount | Structure
Most seamounts are built by one of two volcanic processes, although some, such as the Christmas Island Seamount Province near Australia, are more enigmatic. Volcanoes near plate boundaries and mid-ocean ridges are built by decompression melting of rock in the upper mantle. The lower density magma rises through the crust to the surface. Volcanoes formed near or above subducting zones are created because the subducting tectonic plate adds volatiles to the overriding plate that lowers its melting point. Which of these two process involved in the formation of a seamount has a profound effect on its eruptive materials. Lava flows from mid-ocean ridge and plate boundary seamounts are mostly basaltic (both tholeiitic and alkalic), whereas flows from subducting ridge volcanoes are mostly calc-alkaline lavas.
Seamount | Geochemistry and evolution
Geographical features include:
Explorers Range | Features