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 submarine USS "San Francisco" ran into an uncharted seamount in 2005 at a speed of , sustaining serious damage and killing one seaman. One major seamount risk is that often, in the late of stages of their life, extrusions begin to seep in the seamount. This activity leads to inflation, over-extension of the volcano's flanks, and ultimately flank collapse, leading to submarine landslides with the potential to start major tsunamis, which can be among the largest natural disasters in the world.
Dangers
Seamount
Seamount | Dangers
Yes, seamounts have not been mapped and thus pose a navigational danger. Extrusions begin to seep in the seamount, which leads to inflation, over-extension of the volcano's flanks, and ultimately flank collapse, leading to submarine landslides with the potential to start major tsunamis Yes, Some seamounts have not been mapped and thus pose a navigational danger. Some seamounts have not been mapped and thus pose a navigational danger.
what is a chain of underwater mountains called
user
Seamount
assistant
what can you tell about its geographic features?
user
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.
assistant
how are these chain of mountains formed?
user
Formed millions of years ago by volcanism, they have since subsided far below sea level. This long chain of islands and seamounts extends thousands of kilometers northwest from the island of Hawaii.
assistant
what can you tell about its structure?
user
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
assistant
how can you describe its ecological role?
user
Seamounts are exceptionally important to their biome ecologically, but their role in their environment is poorly understood. Because they project out above the surrounding sea floor, they disturb standard water flow, causing eddies and associated hydrological phenomena that ultimately result in water movement in an otherwise still ocean bottom.
assistant
any type of danger associated with it?
user
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 submarine USS "San Francisco" ran into an uncharted seamount in 2005 at a speed of , sustaining serious damage and killing one seaman. One major seamount risk is that often, in the late of stages of their life, extrusions begin to seep in the seamount. This activity leads to inflation, over-extension of the volcano's flanks, and ultimately flank collapse, leading to submarine landslides with the potential to start major tsunamis, which can be among the largest natural disasters in the world.
Seamount | Dangers
Seamounts are exceptionally important to their biome ecologically, but their role in their environment is poorly understood. Because they project out above the surrounding sea floor, they disturb standard water flow, causing eddies and associated hydrological phenomena that ultimately result in water movement in an otherwise still ocean bottom. Currents have been measured at up to 0.9 knots, or 48 centimeters per second. Because of this upwelling seamounts often carry above-average plankton populations, seamounts are thus centers where the fish that feed on them aggregate, in turn falling prey to further predation, making seamounts important biological hotspots. Seamounts provide habitats and spawning grounds for these larger animals, including numerous fish.
Seamount | Ecological role of seamounts
In an illustration of the potent power of flank collapses, a summit collapse on the northern edge of Vlinder Seamount resulted in a pronounced headwall scarp and a field of debris up to away. A catastrophic collapse at Detroit Seamount flattened its whole structure extensively. Lastly, in 2004, scientists found marine fossils up the flank of Kohala mountain in Hawaii (island). Subsidation analysis found that at the time of their deposition, this would have been up the flank of the volcano, far too high for a normal wave to reach. The date corresponded with a massive flank collapse at the nearby Mauna Loa, and it was theorized that it was a massive tsunami, generated by the landslide, that deposited the fossils.
Seamount | Dangers
This causes a different type of fauna to exist than on the seafloor, and leads to a theoretically higher degree of endemism. However, recent research especially centered at Davidson Seamount suggests that seamounts may not be especially endemic, and discussions are ongoing on the effect of seamounts on endemicity. They "have", however, been confidently shown to provide a habitat to species that have difficulty surviving elsewhere.
Seamount | Ecological role of seamounts
Interactions between seamounts and underwater currents, as well as their elevated position in the water, attract plankton, corals, fish, and marine mammals alike. Their aggregational effect has been noted by the commercial fishing industry, and many seamounts support extensive fisheries. There are ongoing concerns on the negative impact of fishing on seamount ecosystems, and well-documented cases of stock decline, for example with the orange roughy ("Hoplostethus atlanticus"). 95% of ecological damage is done by bottom trawling, which scrapes whole ecosystems off seamounts.
Seamount | Introduction
Complex hydrographical patterns with anticyclones and Taylor columns cause water flow around the summit. Water eddies tend to disrupt this flow. A bottom trawling experiment conducted during research brought up large orange roughy ("Hoplostethus atlanticus") aggregations, as well as bycatch of benthic fauna including sponges, gorgonians, and scleractinian corals.
Sedlo Seamount | Introduction
Thermophilic and hyperthermophilic microorganisms organism have been found at the seamount. Thermophiles found on the seafloor outside Orca Seamount may indicate that thermal waters of Orca Seamount may travel laterally through geological structures or that currents bring in thermal water from Deception Island, an active volcano.
Bransfield Strait | Description
There are several well-documented cases of fishery exploitation, for example the orange roughy ("Hoplostethus atlanticus") off the coasts of Australia and New Zealand and the pelagic armorhead ("Pseudopentaceros richardsoni") near Japan and Russia. The reason for this is that the fishes that are targeted over seamounts are typically long-lived, slow-growing, and slow-maturing. The problem is confounded by the dangers of trawling, which damages seamount surface communities, and the fact that many seamounts are located in international waters, making proper monitoring difficult. Bottom trawling in particular is extremely devastating to seamount ecology, and is responsible for as much as 95% of ecological damage to seamounts.
Seamount | Conservation
The ecological conservation of seamounts is hurt by the simple lack of information available. Seamounts are very poorly studied, with only 350 of the estimated 100,000 seamounts in the world having received sampling, and fewer than 100 in depth. Much of this lack of information can be attributed to a lack of technology, and to the daunting task of reaching these underwater structures; the technology to fully explore them has only been around the last few decades. Before consistent conservation efforts can begin, the seamounts of the world must first be mapped, a task that is still in progress. Overfishing is a serious threat to seamount ecological welfare.
Seamount | Conservation
The Secretary General of the United Nations reported in 2006 that 95 percent of damage to seamount ecosystems worldwide is caused by deep sea bottom trawling. A study published in "Current Biology" suggests a cutoff of is a point which ecological damage increases significantly.
Bottom trawling | Deep sea damage
Corals from seamounts are also vulnerable, as they are highly valued for making jewellery and decorative objects. Significant harvests have been produced from seamounts, often leaving coral beds depleted.
Seamount | Conservation
Water temperatures and salinity of the water masses around Tropic Seamount decrease with increasing depth and ripples indicate that strong ocean currents affect the seamount. A number of separate water masses surround the seamount, which originate from regions such as the North Atlantic, the South Atlantic and Antarctica and are stacked over each other. Corals and sponges and more generally sessile fauna cover parts of the eastern and western spurs of Tropic Seamount, forming multicoloured "forests"; among the animals are glass sponges. The bivalve "Rhinoclama teres" and the echinoids "Echinocyamus scaber", "Palaeotropus josephinae", "Peripatagus cinctus" and "Selenocidaris varispina" have been found on this seamount, as are xenophyophorea.
Tropic Seamount | Environment
Studies have indicated that a seamount functions as an "oasis of life," with a higher species count and more biodiversity than the surrounding seafloor. Although previous analysis has stressed the exceptionalism of the seamount habitat, recent biological analysis, much of it centered on Davidson Seamount, has indicated that this does not necessarily translate into a higher endemic percentage. However, it "is" believed that they provide a refuge for rare species that have difficulty surviving elsewhere. There are reasons that seamounts are biologically important. They rise high in the water column, creating complex current patterns that support life on, around, and above the seamount.
Davidson Seamount | Ecology
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
Some species, including black oreo "(Allocyttus niger)" and blackstripe cardinalfish "(Apogon nigrofasciatus)", have been shown to occur more often on seamounts than anywhere else on the ocean floor. Marine mammals, sharks, tuna, and cephalopods all congregate over seamounts to feed, as well as some species of seabirds when the features are particularly shallow. 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.
Seamount | Ecological role of seamounts
During one survey, a species of cutthroat eel, believed to be found only near Australia, was identified. Corals, echinoderms, and crustaceans make up a large portion of the creatures found on the seamount. These organisms act as indicator species, identifying potential problems in the ecosystem.
New England Seamounts | Biota
With a warming climate, increased rain and increasing glacial meltwater may accelerate edifice collapse. This has potential implications for more landslide hazards in the area of the volcano, and tsunami risks in the lake area.
Yate (volcano) | Future Dangers
In contrast, the knolls in the group that are affected by bottom trawling are mostly barren, with few coral and a completely different ecosystem. In 2001, witnessing the damage of bottom trawling to seamount communities, 19 seamounts off the coast of New Zealand were closed off to bottom trawling, three of them from the Graveyard group. Timed surveys of the seamounts over the years are being used to examine how well a seamount coral community recovers from the effects of dredging over time.
Graveyard Seamounts | Ecology
The seamount suffered a major flank collapse on its southeastern side, over which the present summit was probably formed. The summit supports an ecosystem of mussels, gastropods, tube worms, and others, suggesting that it is an active seeping region.
South Chamorro Seamount | Introduction
An earthquake swarm in 1995 may have been related to an eruption from the seamount. Turbid water above the summit shows evidence of ongoing hydrothermal plume activity. Vailulu'u may breach the surface of the ocean and officially become an island if a high rate of eruptions continue.
Vailuluʻu | Introduction
The volcano has potential to produce huge debris avalanches that could inundate large areas of the Pacific coastal plain. In areas around the volcanoes and downslope toward the coastal plain, more than 100,000 people are potentially at risk from these and other flowage phenomena.
Acatenango | Volcanic hazards
Guyots are also associated with specific lifeforms and varying amounts of organic matter. Local increases in chlorophyll a, enhanced carbon incorporation rates and changes in phytoplankton species composition are associated with guyots and other seamounts.
Guyot | Characteristics
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
Numerous craters and small volcanic cones dot its flanks which bear evidence of sector collapses.
Cadamosto Seamount | Geography and geomorphology
In 1983, , a Royal Australian Navy survey ship, surveyed the area where "Muirfield" was damaged, and charted in detail this previously unsuspected hazard to navigation. The dramatic accidental discovery of the Muirfield Seamount is often cited as an example of limitations in the vertical datum accuracy of some offshore areas as represented on nautical charts, especially on small-scale charts. More recently, in 2005 the submarine ran into an uncharted seamount about 560 kilometers (350 statute miles) south of Guam at a speed of , sustaining serious damage and killing one seaman.
Muirfield Seamount | Introduction
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
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
palmiformis", the sea snail "Lepetodrilus fucensis", the bristle worm "Amphisamytha galapagensis", and the sea spider "Sericosura verenae".
Axial Seamount | Ecology
An eruption from the volcano would threaten the immediate surrounding area, in addition to places downstream near river valleys or downwind that could be affected by ashfall. Lahars (volcanically induced mudslides, landslides, and debris flows) and tephra could extend far from the volcano, and Mount Jefferson may also produce pyroclastic flows, lava domes, and lava flows. Though the population within is only about 800 people, there are more than 550,000 people living with of the volcano. Lava flows from Mount Jefferson or another volcano nearby might form lava domes that could collapse, also yielding pyroclastic flows. Moreover, while basaltic lava flows from surrounding monogenetic vents tend to travel slowly and typically only reach from their source, and therefore would not pose serious hazards to much wildlife or humans, they would still burn and bury anything they encountered.
Mount Jefferson (Oregon) | Recent activity and potential hazards
The most apparent lava flows at a seamount are the eruptive flows that cover their flanks, however igneous intrusions, in the forms of dikes and sills, are also an important part of seamount growth. The most common type of flow is pillow lava, named so after its distinctive shape. Less common are sheet flows, which are glassy and marginal, and indicative of larger-scale flows. Volcaniclastic sedimentary rocks dominate shallow-water seamounts. They are the products of the explosive activity of seamounts that are near the water's surface, and can also form from mechanical wear of existing volcanic rock.
Seamount | Lava types
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
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
Like other large seamounts, Patton acts as an ecological hub for sea life. Dives have revealed that the volcano is heavily encrusted in sea life of various forms, including sea stars, corals, king crabs, demersal rockfish, and other species.
Patton Seamount | Introduction
Several eruptions occurred in 1989 when a scientific expedition was underway on the seamount. These eruptions were accompanied by the discolouration of the water over of length, the release of burning hydrogen and hydrogen sulfide accompanied by the formation of a plume of hydrothermally altered water. The submarine "Cyana" observed activity directly in one summit crater in the form of intense bubbling, while steam and water fountains were seen on the ocean surface. Grey-coloured slicks developed on the ocean surface, which were formed by pyrite, sulfur and volcanic glass plus smaller amounts of cinnabar, cubatine and quenstedtite. The events caused changes in the pH of the water on the seamount and increased methane concentrations.
Macdonald seamount | 1989 events
While the Clipperton Fracture Zone is located just north, the East Pacific Rise lies east of the seamounts; Sasha Seamount lies just from the Rise. It appears to contain a magma chamber at that latitude and seems to have produced voluminous volcanism that generated a topopgraphic elevation that is now associated with the Lamont seamounts. The volcanism is quite young and accompanied by hydrothermal activity; seafloor spreading here proceeds at a rate of and a volcanic eruption in 2003-2006. The seamounts have produced hyaloclastites, sheet- and lobe-like lava flows as well as pillow lavas and talus. The total volume of each seamount ranges between and the volume increases away from the East Pacific Rise, which along with other patterns indicates a progressive development of the seamount as they move away from the East Pacific Rise.
Lamont seamount chain | Geology
The floor of the seamount is generally covered by a dense layer of seaweed, dominated by the "Cystoseira" species, a seaweed found in deeper areas. In shallower depths less than from the surface there are populations of "Laminaria" (large colonies of chestnut seaweeds). The Department of Oceanography and Fisheries at the University of the Azores (Ponta Delgada) monitors and studies these species annually through scientific missions to the reef and surrounding islets.
Dollabarat | Biome
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
If the unstable piece of rock fell, it would very quickly move and displace extremely large amounts of water. When a landslide generates a tsunami, it can produce waves that cause very severe damage, especially when the energy of the waves is amplified by being trapped in an inlet of the coast.
Mount Breakenridge | Potential landslide and tsunami hazard
In addition there are long gullies formed either by erosional or volcanic processes, as well as parasitic vents and volcanic ridges.
Tropic Seamount | Local
There is evidence that seamounts can host concentrations of biologic diversity, each with its own unique local ecosystem; they seem to affect oceanic currents, resulting among other things in local concentration of plankton which in turn attracts species that graze on it, and indeed are probably a significant overall factor in biogeography of the oceans. They also may serve as way stations in the migration of whales and other pelagic species. Despite being poorly studied, they are heavily targeted by commercial fishing, including dredging. In addition they are of interest to potential seabed mining. The overall goal of CenSeam is "to determine the role of seamounts in the biogeography, biodiversity, productivity, and evolution of marine organisms, and to evaluate the effects of human exploitation on seamounts." To this effect, the group organizes and contributes to various research efforts about seamount biodiversity.
Global Census of Marine Life on Seamounts | Introduction
The seamount is a guyot which rises about to a depth of -, where a flat top is covered by early Cretaceous limestone that contains gastropods, green algae and red algae from that time. Erimo Seamount is cut by normal faults that run parallel to the Kuril-Kamchatka Trench, and the seamount is tilting and beginning to break apart as its subduction starts. It has a volume of about , making it a mid-sized seamount by Pacific Ocean seamount standards, with an northeast-southwest elongated shape and a maximum width of and recognizable rift zones. The crust underneath Erimo contains the magnetic anomaly M8 and has an age of about 120 million years.
Erimo Seamount | Local
A common but much smaller fish was "Aldrovandia phalacra". Twenty-six species of cephalopods were collected including squid such as "Mastigoteuthis agassizii" and "Mastigoteuthis magna". Other invertebrates caught by trawls dragged along the seamount surface included 46 species of crustacean such as the prawns "Sergestes spp." and "Acanthephyra spp.", and the shrimp "Pasiphaea spp". Also present was the bank-forming deepwater coral "Lophelia pertusa", which supported a community of worms, hydroids and other corals. Brittle stars, especially "Ophiomusium lymani", were numerous as were the sea urchin "Echinus affinis", the sea star "Neomorphaster forcipatus", mysids and various scyphozoans.
Bear Seamount | Biodiversity
Vesteris Seamount displays high biological productivity. The summit area of the seamount is densely inhabited by mats and biogenic structures formed by ascidians, bryozoans, polychaetes and sponges; in other sectors of the volcano sponges are accompanied by crinoids. Actinians, brittle stars, hydrozoans, molluscs, radiolarians and starfish are also found, as well as foraminiferal sands. Similar lifeforms are also found on the lower slopes of the seamount. Traces of endolithic fungi have been found in rock samples from the seamount. Life on Vesteris has formed a variety of structures, including hedges, mats, mounds, spurs and thickets, and a dense layer of biogenic sediments and living specimens covers large areas of the upper Vesteris Seamount.
Vesteris Seamount | Biology and climate
The summit of the volcano is dominated by a carpet of "Hinnites multirugosus", which forms the base of a dense ecosystem of sponges and other small, sessile organisms. The species is otherwise scarce in its distribution in the Pacific; its abundance is accommodated by the scarcity of its chief predator, the sea star "Orthasterias koehleri". The reason for the sea star's disparity is unknown, as it is extremely common on nearby seamounts. The steeper flanks of the volcanoes are carpeted by coralline algae of the "Lithothamnion" and "Lithophyllum" genera. In some areas, "Borgiola pustulosa" is more common. Red-colored colonies of demosponge and related species predominant the ecosystem, which includes sea urchins, sponges, algae, anemones, and gastropods.
Cobb Seamount | Biology
Patton Seamount is ecologically vibrant: geologist Randy Keller of the Oregon State University once said "...it's just astonishing how much there is around you. You see rocky outcroppings and there's life everywhere—sponges and sea stars." Patton Seamount, like many other seamounts, serves as an "oasis of life" for resident organisms. Isolated populations found on seamounts like Patton have been shown to have high levels of endemism and specialization, and Patton Seamount is almost completely encrusted in life. Limited-scale fishing operations and scientific investigations were carried around in the 80s and 90s, mostly due to the rough nature of the seamounts, and the difficulty of sampling at such depths.
Patton Seamount | Ecology
Large landslides and late volcanic activity affected the seamount, cutting large scars into its flanks and forming cones on its summit plateau, respectively. Volcanic activity at Tropic Seamount commenced almost 120 million years ago and ended about 60 million years ago. Later, sedimentation commenced on the seamount leading to the deposition of manganese crusts and pelagic sediments; iron and manganese accumulated in crusts over time beginning a few tens of millions of years ago.
Tropic Seamount | Introduction
The event involved the movement of cubic meters of volcanic material. A region of 10 to 13 km (4 to 5 sq mi) of the summit was altered and populated by bus-sized pillow lava blocks, precariously perched along the outer rim of the newly formed crater. "Pele's Vents," an area on the southern side, previously considered stable, collapsed completely into a giant pit, renamed "Pele's Pit". Strong currents make submersible diving hazardous in the region.
Lōʻihi Seamount | 1996 earthquake swarm
Given its shallow depth, Bowie Bank is a potential marine hazard. Waves up to high have been recorded along the British Columbia Coast during heavy weather, enough to expose the bank by wave troughs and cause devastation to any vessel transiting the seamount. For this reason, Environment Canada has recognized Bowie Seamount as a hazard to navigation, and it is avoided by shipping vessels.
Bowie Seamount | Marine hazard
Henry Seamount is a rare example of a seamount that is hydrothermally active despite being an extinct volcano. The summit area is densely covered with clam deposits and structures that appear to be deposits from hydrothermal venting. Radiocarbon dating on vesicomyid clams, which occur at cold seeps and hydrothermal vents, have yielded ages of less than 3,350 years, implying recent hydrothermal activity. The chemistry of baryte blocks - which also formed through hydrothermal venting - implies that the hydrothermal fluids had a low temperature. No unambiguous evidence of present-day fluid venting was found during research cruises and there are no heat flow anomalies that could be related to the seamount.
Henry Seamount | Hydrothermal activity
Seamounts that are not clearly linked to a mantle plume indicate that regional mantle composition and tectonic activity may also play important roles in producing intraplate volcanism.
Ocean island basalt | Introduction
Muir Seamount is a seamount (underwater volcano), located at . It is located in the Bermuda rise, a seismically active region, and was the site of an earthquake on 24 March 1978. Fourteen core samples of up to 125,000 years of age were collected off of Muir Seamount, ranging in depth to more than . These samples were used to analyse the weight percentage of carbonate over time on the ocean floor, which in turn would provide clues to the oceanic environment over time. Overall concentrations were most stable at of depth. This was interpreted as indicating an increase in flow form colder waters of Antarctic flow, and the stagnation of the North American flows.
Muir Seamount | Introduction
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
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
Geohazards are associated with geological activity, geotechnical features and environmental conditions. Shallow geohazards are those occurring at less than below the seafloor. Information on the potential risks associated with these phenomena is acquired through studies of the geomorphology, geological setting and tectonic framework in the area of interest, as well as with geophysical and geotechnical surveys of the seafloor. Examples of potential threats include tsunamis, landslides, active faults, mud diapirs and the nature of the soil layering (presence of karst, gas hydrates, carbonates). In cold regions, gouging ice features are a threat to subsea installations, such as pipelines. The risks associated with a particular type of geohazard is a function of how exposed the structure is to the event, how severe this event is and how often it occurs (for episodic events).
Offshore geotechnical engineering | Geohazards
Present-day activity occurs at the top of the Monowai cone, and manifests itself in the form of earthquakes, discoloured water, emission of gases and pumice rafts, rumbling sounds and upwelling water. Underwater, this activity generates cones, debris flows, lava flows and pyroclastic flows as well as sector collapses and lava dome growth, which has caused the summit of Monowai cone to shift southward. Several seismic swarms have been observed on Monowai, including a strong swarm in May 2002 that may be associated with a sector collapse, and sound waves from the volcano have been recorded as far aways as Ascension Island in the Atlantic Ocean.
Monowai (seamount) | Eruption history
The potential destruction that could be seen in the event of a landslide and accompanying tsunami would be devastating. These types of tsunamis have enough strength to cause a serious threat for any village nearby and have even been known to remove all the sand off a beach after moving through the area. Most at risk is the resort village of Harrison Hot Springs, which is located at the south end of the lake. Other towns that would be reached by the water are Port Douglas, which is at the head of the lake, Fraser Valley, and even Whatcom County, Washington.
Mount Breakenridge | Potential destruction and the areas and industries at risk
They appear to have been formed under the influence both of fracture zones and of a melt anomaly that also formed a topographic anomaly west of the Lamont seamount chain along with elongated volcanic structures; a bathymetric swell is also noted around the seamounts as well as a deep depression that may be an isostatic moat. The volcanism may be ultimately the consequence of hotspot activity.
Lamont seamount chain | Geology
The area is home to rare and endangered species, including sperm whales, fin whales, sei whales and Kemp’s ridley sea turtles.
Northeast Canyons and Seamounts Marine National Monument | Biology and ecology
These include the Hawaiian (Emperor), Mariana, Gilbert, Tuomotu and Austral Seamounts (and island groups) in the north Pacific and the Louisville and Sala y Gomez ridges in the southern Pacific Ocean. In the North Atlantic Ocean, the New England Seamounts extend from the eastern coast of the United States to the mid-ocean ridge. Craig and Sandwell noted that clusters of larger Atlantic seamounts tend to be associated with other evidence of hotspot activity, such as on the Walvis Ridge, Bermuda Islands and Cape Verde Islands. The mid-Atlantic ridge and spreading ridges in the Indian Ocean are also associated with abundant seamounts.
Seamount | Grouping
Henry Seamount is located within the Canary Current Large Marine Ecosystem. Deepwater corals, holothurians, red worms, starfish, gastropods and xenophyophore, a coral stem and shell fragments have also been reported. Underwater cameras have observed "graveyards" of thousands of clams on the seamount. The occurrence of "Abyssogena southwardae" at Henry Seamount has been reported.
Henry Seamount | Biology
A seamount such as Davidson is an underwater volcano; this one rises above the surrounding ocean floor. Although there are over 30,000 seamounts in the Pacific Ocean alone, only about 0.1% of them have been explored. The aqueous environment of the seamount means that it behaves differently from volcanoes on land. Its surface is composed mostly of blocky lava flows, although some pillow lava, which is the typical lava type of a seamount, prevails at the deeper flank. The summit is composed of layered deposits of volcanic ash and pyroclastic material. These rocks indicate mildly explosive eruptions of gas-rich lava near the summit of the volcano.
Davidson Seamount | Geology
Lava flows or landslide deposits appear to surround a number of the seamounts. A number of processes has been proposed to explain the formation of seamounts close to spreading ridges. In the case of Rano Rahi, both line-like sources and point-like sources of magma may be involved, with a common source of magma that results in a tradeoff between the sizes of neighbouring seamount chains. Seismic tomography has identified low-velocity material beneath the seamounts which may be flows in the mantle. The neighbouring Pukapuka ridge appears to be related to the Rano Rahi seamounts, which are located east of its eastern end and form a wedge-shaped extension thereof.
Rano Rahi seamounts | Geology
Scour marks have been observed. The currents sweep down the seamount slopes and may act to remove sediment from the seamount surface; this also results in sediments accumulating to form steep slopes that undergo landsliding. Most of the sediments however are transported upslope; those which do end up at the bottom of the seamount form talus deposits around Horizon Guyot.
Horizon Guyot | Present state
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
A number of sea animals and fish are encountered on the seamount; active fisheries existed at Vema Seamount and caused the disappearance of some animal species.
Vema Seamount | Introduction
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
Although there is no evidence of past mudflows of such size, lahars could reach as far as the coast, affecting a number of towns and infrastructure such as roads, antennas and small hydropower plants. According to the 2007 census, 110,481 people lived in the provinces that span Coropuna and lie downstream of it. Lava flows are also a potential danger at Coropuna. Other hazards with lesser probabilities are directed volcanic blasts, lava dome collapses, fast-moving massive pyroclastic flows and flows of pumice and volcanic ash, lava bombs and shock waves from volcanic explosions.
Coropuna | Hazards and monitoring
Similar bacterial mats are found commonly on seamounts created by underwater volcanoes, and by the instense volcanism at hydrothermal vents. Hydrothermal venting favors the growth of bacterial mats in which "Sulfurimonas" occurs, such as at the Loihi, Axial, Vailulu'u, and Suiyo Seamounts, and the Mariana and Kermadec Arcs.
Sulfurimonas | Habitat
A gap near the seamount, known as the Ballons gap, is interpreted as being due to excess volcanism from the seafloor spreading process. A ridge just south of the seamount, the Antipodes Fracture Zone, is interpreted as having been built by a combination of compression and volcanic activity associated with the triple-junction Bellingshausen-Marie Byrd Land plate boundary nearby.
Bollons 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
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
The population is thought to be between 1,505 and 52,734. Accurate numbers are hard to estimate due to cloud coverage over its range. Some of its natural threats include birds, snakes, and the giant civet. Mount Awu can also be considered a natural threat as well, since it is an active and deadly volcano on the island. Anthropogenic causes include habitat loss or fragmentation, the introduction of cats and dogs to the island, population density increases in its territory, and pet trade.
Sangihe tarsier | Threats
The canyons and seamounts are celebrated for their rich biological diversity. The steep slopes of the canyons and seamounts interact with oceanographic currents to create localized eddies, causing upwelling. The currents lift nutrients to surface waters, fueling an outburst of phytoplankton and zooplankton that form the base of the food chain. These plankton draw large schools of small fish, and those fish draw even larger predators such as whales, sharks, tunas and seabirds to the area. In all, “the geology, currents, and productivity create diverse and vibrant ecosystems.” As a result, the area has been the subject of “intense scientific interest” and discovery since the 1970s.
Massachusetts Lobstermen's Association v. Ross | History
It is important that citizens of the area and also the rest of the world know about the danger that is possible due to the instability of the mountainside and the potential for a resulting megatsunami. Tsunamis are an unstoppable force but people need to be proactive, educated, and prepared to try to lessen the damage and loss through evacuation planning and be ready to assist in recovery after the fact. People's lives, property, homeland, and financial livelihoods are at risk, as well as the species of the surrounding ecosystem and the landscape itself being in the path of danger.
Mount Breakenridge | Social, environmental, ecological, and economic significance
Whether there was Holocene activity 5,000–6,000 years ago or present-day hydrothermal activity is unclear. A variety of lifeforms are found both on Vesteris Seamount and within its rocks. Layers of sponges and bryozoans cover the upper parts of the seamount and form structures like mounds. This ecosystem has been compared to coral reefs.
Vesteris Seamount | Introduction
A number of seamounts occur in the Western Pacific Ocean which often form lines and groups and have the appearance of drowned atolls, with flat tops at depths of below sea level. They often appear to be shallower than would be expected from plate tectonics and the normal thermal subsidence of the oceanic crust. Their formation has been explained by hotspot volcanism in the region of present-day French Polynesia although many of them do not appear to have originated from simple hotspot mechanisms. These seamounts are considered to be part of the Darwin Rise, which includes MIT. About five different hotspots were active in French Polynesia within the last twenty million years.
MIT Guyot | Regional setting
Within areas of the vents, tephra may form deposits with thicknesses of up to , though they only reach thicknesses of at further distances beyond . Because lava flows move slowly, they can be outmaneuvered by animals and humans, though they do pose a threat to streams and rivers, which they may dam or divert, leading to potential flood risks. If Mount Bachelor were to erupt, it would significantly affect the ski industry on the volcano, endangering visitors. An eruption from Mount Bachelor, the Three Sisters to the north, or another nearby vent in the Mount Bachelor Chain may be unlikely, but any would pose threats to the ski area.
Mount Bachelor | Potential hazards
26% to 44% of them could not be identified and are thus believed to be new, and about a third are seemingly present only in the seamount environment. Damage from trawling was also examined, and on the most heavily affected seamounts it had destroyed coral aggregations, removed 46% of species, and reduced net biomass by over half. Following the study, the proposed marine reserve, the "Tasmanian Seamount Community" or "Tasmanian Seamounts Marine Reserve" was created as part of the Environment Protection and Biodiversity Conservation Act 1999. The reserve banned fishing, especially trawling, within an area of . It contained 70 seamounts, a fifth of the known Tasmanian seamounts, all of which were low-trawl areas and thus still in relatively unaffected form.
Tasmanian Seamounts | Ecology
The unique ecological condition of the Great Meteor Seamount is shown by the many endemic copepod and nematode species.
Great Meteor Seamount | Ecology
Overfishing (as in the rate of depletion) at the Cross seamount appeared to be quite high, causing concerns. However, as much of the population seems to originate elsewhere, this loss is most likely accounted for. Problems with fishery interaction were eliminated, as 90% of the recaptures were in the local area. However, it was not possible to create a model on the overfishing of juveniles, as there was insufficient data to predict this accurately.
Cross Seamount | 1995 tagging project
This volcanic activity is almost certainly forced by the interaction between the Antarctic-Pacific Ridge and the Foundation hotspot. The main Foundation Seamounts appear to be aseismic; if earthquake activity occurs at the intersection of the Foundation chain with the Antarctic Pacific Ridge, it is drowned out by the general ridge seismicity.
Foundation Seamounts | Activity
Suspension feeders, such as gorgonian sea fans and the cold-water corals like Lophelia pertusa, often dominate the rich benthic (seafloor-dwelling) communities. The enhanced abundance and diversity of fauna is not limited to benthic species, as fish are known to aggregate over seamounts. Unfortunately, this knowledge has led to increasing commercial exploitation of seamount fish by the fishing industry, and a number of seamount fish populations have already been depleted. Part of HERMIONE research will assess the threats and impacts of human activities on seamounts, including comparing data from seamounts in different stages of fisheries exploitation to understand more about the impacts of fishing activities., both on target species and non-target species, and their habitats.
Hotspot Ecosystem Research and Man's Impact On European Seas | Seamounts
Mount Breakenridge is the subject of intensive study by government geologists due to the location of a fracture or shear zone on the mountainside above Harrison Lake. Researchers have identified the shear zone as a major risk for collapse into Harrison Lake, one of British Columbia's largest and deepest lakes, causing a large megatsunami. The fracture is a group of cracks caused by tension from a large and unstable piece of rock, and was most likely made more unstable by the abundant rain and seismic activity of the area. Supermarine landslides, which is what is feared in the case of Mount Breakenridge, disrupt the body of water from above when debris falls in, and then the energy from the debris travels into the water.
Mount Breakenridge | Potential landslide and tsunami hazard
The crust underneath these seamounts tends to subside as it cools, and thus the islands and seamounts sink. Continued subsidence balanced by upward growth of the reefs led to the formation of thick carbonate platforms. Sometimes volcanic activity continued even after the formation of the atoll or atoll-like structure, and during episodes where the platforms rose above sea level erosional features such as channels and blue holes developed. The formation of many seamounts has been explained by the hotspot theory, which suggests that the chains of volcanoes become progressively older along the length of the chain, with an erupting volcano only at one end of the system.
Resolution Guyot | Regional setting
Minor hydrothermal explosions could still potentially be dangerous, as the ejection of ballistic blocks or tall waves could threaten people standing near the lake, traveling at speeds from . Landslides could threaten visitors to the national park or researchers by creating tsunami-sized waves, also potentially damaging infrastructure surrounding the lake.
Mount Mazama | Recent activity and potential hazards
Part of the landward margin of the trench close to Daiichi-Kashima is uplifted, perhaps as a consequence of the subduction of the seamount, and there is periodic earthquake activity in front of Daiichi-Kashima seamount with magnitude 7 earthquakes about every 20 years. The seamount might also influence the segmentation of the trench and its earthquakes, considering that the rupture of the 2011 Tohoku earthquake spanned the trench length between Erimo Seamount and Daiichi-Kashima. The other seamounts in the area will likely be subducted after Daiichi-Kashima has been.
Daiichi-Kashima Seamount | Relation to the Japan Trench
The Condor seamount has sediment of various types, including those of volcanic origin, as well as sediments composed of organic matter derived from living organisms, that, in some areas, form thick plates, sometimes with 15 cm. These sediments can contain several species, including gorgonians, sponges and other organisms.
Condor seamount | Sedimentary areas
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
Mazama is considered dormant, but it remains monitored by the United States Geological Survey Cascades Volcano Observatory. Future eruptions would likely take place near the western side of the complex and within the caldera rim; they could occur underwater. The ejection of lava rich in gas from shallow water could produce huge ash columns, but submarine eruptions at deeper depths may decrease the explosiveness of the event. Nonetheless, the rapid mixing of water and lava could produce dangerous pyroclastic surges, which are more gaseous and less solid than pyroclastic flows. Such flows could pass over topographic barriers, move rock fragments at , and travel several miles from their vent.
Mount Mazama | Recent activity and potential hazards
Between 700 and 900 m depth there are large aggregations of sponges in the Condor seamount. These aggregations are dominated by the presence of glass sponge ("Pheronema carpenteri") and are also considered as habitats of conservation importance.
Condor seamount | Aggregations of sponges
Possibly, as such a seamount or a seamount chain subducted it indented the trenches, forming a re-entrant.
Erimo Seamount | Regional
rising watertable) is also a major threat.
Troglofauna | Threats to troglofauna
Many seamounts are biodiversity hotspots, as they interact with ocean currents enhancing the biological productivity around them. In the case of the northeast Atlantic seamounts, deep ocean currents are diverted at the seamount inducing upwelling. Outcropping rocks permit the settlement of species that would not find suitable substrates on sediment covered seafloor. Underwater video has identified a number of animals living on Coral Patch Seamount, but in general animals are rare and corals do not form large colonies. These include actinians, anemones, asteroids, barnacles, bivalves, brachiopods, dendrophylliid corals, "Eguchipsammia", "Lophelia pertusa" and "Madrepora oculata" corals, crinoids, echinoids, octocorals, and sponges, most of which are attached to bedrock.
Coral Patch Seamount | Life
This environment has been compared to a coral reef. The seamount lies close to the polar front with the East Greenland Current transporting freshwater from ice melt and ice to the seamount. The sea above Vesteris is covered by sea ice for most of the year except for August and September, and water temperatures on the surface of the seamount are around in summer.
Vesteris Seamount | Biology and climate
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
South Chamorro Seamount is host to a variety of fauna, including mussels, gastropods, tube worms, and galatheid crabs. A borehole observatory on the summit produced 20,000 litres of microbially-altered fluid per day for study. These organisms are supported by low-temperature springs from the fissures surrounding the summit zone. The mussels are probably of the genus Bathymodiolus, which require a high concentration of methane in their food source. The fluid composition and the biological community suggests that the summit region is an active cold seep region.
South Chamorro Seamount | Ecology
The movement and strength of ocean eddies are altered when they interact with Vema Seamount, with Agulhas eddies often splitting apart at the seamount.
Vema Seamount | Geology
According to the "Federal Register", the Northeast Canyons and Seamounts Marine National Monument is the smallest area feasible to provide necessary management; designating a smaller zone would lead to an inaccurate interpretation and protection of biodiversity within the fragile area. The designation of the Marine National Monument occurred after numerous meetings and deliberations with stakeholders including conservationists, community members, fishermen, and local businesses; administrative officials gathered social, economic, and environmental data to inform the creation of the Northeast Canyons and Seamounts Marine National Monument. Residing at depths of ~4,000 meters, deep sea corals and other foundational species are highly sensitive to anthropogenic disturbances such as bottom trawling and mining extractions.
Northeast Canyons and Seamounts Marine National Monument | Legal issues
The surface of the seamount also provides a substrate upon which organisms can attach themselves and grow. This in turn supports the species that feed on them, in turn supporting the whole ecological food web. Scientists have found that seamounts often provide a habitat for endemic species that are not found anywhere else. Davidson Seamount is among the best biologically described seamounts worldwide. Six major expeditions to the volcano have yielded over 60,000 species observations. scientists have observed and recorded 168 species of megafauna on the seamount. Of these, about 7% of the species at Davidson are endemic, meaning they live only at Davidson.
Davidson Seamount | Ecology
Thermal subsidence lowered the drowned seamount to its present depth. After a hiatus, sedimentation commenced on the seamount and led to the deposition of manganese crusts and pelagic sediments, some of which were later modified by phosphate.
Wōdejebato | Introduction