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98-716: The Pilbara Craton is an old and stable part of the continental lithosphere located in the Pilbara region of Western Australia . The Pilbara Craton is one of only two pristine Archaean 3.8–2.7 Ga (billion years ago) crusts identified on the Earth, along with the Kaapvaal Craton in South Africa . The youngest rocks are 1.7 Ga old in the historic area assigned to the Craton. Both locations may have once been part of

196-460: A supercritical fluid at such temperatures. The critical point of (pure) water is 375 °C (707 °F) at a pressure of 218  atmospheres . However, introducing salinity into the fluid raises the critical point to higher temperatures and pressures. The critical point of seawater (3.2 wt. % NaCl) is 407 °C (765 °F) and 298.5 bars, corresponding to a depth of ~2,960 m (9,710 ft) below sea level. Accordingly, if

294-399: A chemical highly toxic to most known organisms, to produce organic material through the process of chemosynthesis . The vents' impact on the living environment goes beyond the organisms that lives around them, as they act as a significant source of iron in the oceans, providing iron for the phytoplankton. The oldest confirmed record of a "modern" biological community related with a vent is

392-555: A deposit thought to be located at the mouth of a river due to certain characteristics like rounded and sorted grains. Extensive field mapping and petrogenetic analysis has since shown the setting for the purported microfossils to be hydrothermal and this is widely supported. Consequently, many alternative abiotic explanations have been proposed for the filamentous microstructures including carbonaceous rims around quartz spherules and rhombs, witherite self-assembled biomorphs and haematite infilled veinlets. The carbonaceous matter composing

490-537: A depth of about 600 kilometres (370 mi). Continental lithosphere has a range in thickness from about 40 kilometres (25 mi) to perhaps 280 kilometres (170 mi); the upper approximately 30 to 50 kilometres (19 to 31 mi) of typical continental lithosphere is crust. The crust is distinguished from the upper mantle by the change in chemical composition that takes place at the Moho discontinuity . The oldest parts of continental lithosphere underlie cratons , and

588-414: A few tens of millions of years but after this becomes increasingly denser than asthenosphere. While chemically differentiated oceanic crust is lighter than asthenosphere, thermal contraction of the mantle lithosphere makes it more dense than the asthenosphere. The gravitational instability of mature oceanic lithosphere has the effect that at subduction zones, oceanic lithosphere invariably sinks underneath

686-467: A host that contains methanotrophic endosymbionts; however, the latter mostly occur in cold seeps as opposed to hydrothermal vents. While chemosynthesis occurring at the deep ocean allows organisms to live without sunlight in the immediate sense, they technically still rely on the sun for survival, since oxygen in the ocean is a byproduct of photosynthesis. However, if the sun were to suddenly disappear and photosynthesis ceased to occur on our planet, life at

784-417: A hydrothermal fluid with a salinity of 3.2 wt. % NaCl vents above 407 °C (765 °F) and 298.5 bars, it is supercritical. Furthermore, the salinity of vent fluids have been shown to vary widely due to phase separation in the crust. The critical point for lower salinity fluids is at lower temperature and pressure conditions than that for seawater, but higher than that for pure water. For example,

882-549: A light other than sunlight for photosynthesis. New and unusual species are constantly being discovered in the neighborhood of black smokers. The Pompeii worm Alvinella pompejana , which is capable of withstanding temperatures up to 80 °C (176 °F), was found in the 1980s, and a scaly-foot gastropod Chrysomallon squamiferum in 2001 during an expedition to the Indian Ocean 's Kairei hydrothermal vent field . The latter uses iron sulfides ( pyrite and greigite) for

980-429: A mean density of about 2.7 grams per cubic centimetre or 0.098 pounds per cubic inch) and underlies the continents and continental shelves. Oceanic lithosphere consists mainly of mafic crust and ultramafic mantle ( peridotite ) and is denser than continental lithosphere. Young oceanic lithosphere, found at mid-ocean ridges , is no thicker than the crust, but oceanic lithosphere thickens as it ages and moves away from

1078-650: A net source of metals such as Fe and Mn to the oceans, they can also scavenge other metals and non-metalliferous nutrients such as P from seawater, representing a net sink of these elements. Life has traditionally been seen as driven by energy from the sun, but deep-sea organisms have no access to sunlight, so biological communities around hydrothermal vents must depend on nutrients found in the dusty chemical deposits and hydrothermal fluids in which they live. Previously, benthic oceanographers assumed that vent organisms were dependent on marine snow , as deep-sea organisms are. This would leave them dependent on plant life and thus

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1176-457: A strong, solid upper layer (which he called the lithosphere) above a weaker layer which could flow (which he called the asthenosphere ). These ideas were expanded by the Canadian geologist Reginald Aldworth Daly in 1940 with his seminal work "Strength and Structure of the Earth." They have been broadly accepted by geologists and geophysicists. These concepts of a strong lithosphere resting on

1274-618: A thick mat which attracts other organisms, such as amphipods and copepods , which graze upon the bacteria directly. Larger organisms, such as snails, shrimp, crabs, tube worms , fish (especially eelpout , cutthroat eel , Ophidiiformes and Symphurus thermophilus ), and octopuses (notably Vulcanoctopus hydrothermalis ), form a food chain of predator and prey relationships above the primary consumers. The main families of organisms found around seafloor vents are annelids , pogonophorans , gastropods , and crustaceans, with large bivalves , vestimentiferan worms, and "eyeless" shrimp making up

1372-871: A tracer of hydrothermal activity is radon . As all naturally occurring isotopes of Rn are radioactive, Rn concentrations in seawater can also provide information on hydrothermal plume ages when combined with He isotope data. The isotope radon-222 is utilized for this purpose as Rn has the longest half-life of all naturally occurring radon isotopes of roughly 3.82 days. Dissolved gases, such as H 2 , H 2 S, and CH 4 , and metals, such as Fe and Mn, present at high concentrations in hydrothermal vent fluids relative to seawater may also be diagnostic of hydrothermal plumes and thus active venting; however, these components are reactive and are thus less suitable as tracers of hydrothermal activity. Hydrothermal plumes represent an important mechanism through which hydrothermal systems influence marine biogeochemistry . Hydrothermal vents emit

1470-510: A type of chemosynthetic based ecosystems (CBE) where primary productivity is fuelled by chemical compounds as energy sources instead of light ( chemoautotrophy ). Hydrothermal vent communities are able to sustain such vast amounts of life because vent organisms depend on chemosynthetic bacteria for food. The water from the hydrothermal vent is rich in dissolved minerals and supports a large population of chemoautotrophic bacteria. These bacteria use sulfur compounds, particularly hydrogen sulfide ,

1568-632: A vent fluid with a 2.24 wt. % NaCl salinity has the critical point at 400 °C (752 °F) and 280.5 bars. Thus, water emerging from the hottest parts of some hydrothermal vents can be a supercritical fluid , possessing physical properties between those of a gas and those of a liquid . Examples of supercritical venting are found at several sites. Sister Peak (Comfortless Cove Hydrothermal Field, 4°48′S 12°22′W  /  4.800°S 12.367°W  / -4.800; -12.367 , depth 2,996 m or 9,829 ft) vents low salinity phase-separated , vapor-type fluids. Sustained venting

1666-400: A weak asthenosphere are essential to the theory of plate tectonics . The lithosphere can be divided into oceanic and continental lithosphere. Oceanic lithosphere is associated with oceanic crust (having a mean density of about 2.9 grams per cubic centimetre or 0.10 pounds per cubic inch) and exists in the ocean basins . Continental lithosphere is associated with continental crust (having

1764-613: A wide range of elements to the world's oceans, thus contributing to global marine biogeochemistry . Relative to the majority of the deep sea, the areas around hydrothermal vents are biologically more productive, often hosting complex communities fueled by the chemicals dissolved in the vent fluids. Chemosynthetic bacteria and archaea found around hydrothermal vents form the base of the food chain , supporting diverse organisms including giant tube worms , clams, limpets , and shrimp. Active hydrothermal vents are thought to exist on Jupiter 's moon Europa and Saturn 's moon Enceladus , and it

1862-467: A wide variety of trace metals into the ocean, including Fe , Mn , Cr , Cu , Zn , Co , Ni , Mo , Cd , V , and W , many of which have biological functions. Numerous physical and chemical processes control the fate of these metals once they are expelled into the water column. Based on thermodynamic theory, Fe and Mn should oxidize in seawater to form insoluble metal (oxy)hydroxide precipitates; however, complexation with organic compounds and

1960-445: Is a particularly useful tracer of hydrothermal activity. This is because hydrothermal venting releases elevated concentrations of helium-3 relative to seawater, a rare, naturally occurring He isotope derived exclusively from the Earth's interior. Thus, the dispersal of He throughout the oceans via hydrothermal plumes creates anomalous seawater He isotope compositions that signify hydrothermal venting. Another noble gas that can serve as

2058-404: Is able to convect. The lithosphere–asthenosphere boundary is defined by a difference in response to stress. The lithosphere remains rigid for very long periods of geologic time in which it deforms elastically and through brittle failure, while the asthenosphere deforms viscously and accommodates strain through plastic deformation . The thickness of the lithosphere is thus considered to be

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2156-841: Is known as the "nonbuoyant plume" phase. Once the plume is neutrally buoyant, it can no longer continue to rise through the water column and instead begins to spread laterally throughout the ocean, potentially over several thousands of kilometers. Chemical reactions occur concurrently with the physical evolution of hydrothermal plumes. While seawater is a relatively oxidizing fluid, hydrothermal vent fluids are typically reducing in nature. Consequently, reduced chemicals such as hydrogen gas , hydrogen sulfide , methane , Fe , and Mn that are common in many vent fluids will react upon mixing with seawater. In fluids with high concentrations of H 2 S, dissolved metal ions such as Fe and Mn readily precipitate as dark-colored metal sulfide minerals (see "black smokers"). Furthermore, Fe and Mn entrained within

2254-475: Is located near Nafanua volcanic cone , American Samoa . In 1993, already more than 100 gastropod species were known to occur in hydrothermal vents. Over 300 new species have been discovered at hydrothermal vents, many of them "sister species" to others found in geographically separated vent areas. It has been proposed that before the North American Plate overrode the mid-ocean ridge , there

2352-417: Is not yet known what significance, if any, supercritical venting has in terms of hydrothermal circulation, mineral deposit formation, geochemical fluxes or biological activity. The initial stages of a vent chimney begin with the deposition of the mineral anhydrite . Sulfides of copper , iron , and zinc then precipitate in the chimney gaps, making it less porous over the course of time. Vent growths on

2450-416: Is rapid which then leads to halving of nucleotide concentration, weak nucleotide catalysis of CO 2 fixation promotes little to protocell growth and division. In biochemistry, reactions with CO 2 and H 2 produce precursors to biomolecules that are also produced from the acetyl-CoA pathway and Krebs cycle which would support an origin of life at deep sea alkaline vents. Acetyl phosphate produced from

2548-420: Is released by the magma. The proportion of each varies from location to location. In contrast to the approximately 2 °C (36 °F) ambient water temperature at these depths, water emerges from these vents at temperatures ranging from 60 °C (140 °F) up to as high as 464 °C (867 °F). Due to the high hydrostatic pressure at these depths, water may exist in either its liquid form or as

2646-462: Is speculated that ancient hydrothermal vents once existed on Mars . Hydrothermal vents have been hypothesized to have been a significant factor to starting abiogenesis and the survival of primitive life . The conditions of these vents have been shown to support the synthesis of molecules important to life. Some evidence suggests that certain vents such as alkaline hydrothermal vents or those containing supercritical CO 2 are more conducive to

2744-426: Is the thermal diffusivity (approximately 1.0 × 10  m /s or 6.5 × 10  sq ft/min) for silicate rocks, and t {\displaystyle t} is the age of the given part of the lithosphere. The age is often equal to L/V, where L is the distance from the spreading centre of mid-oceanic ridge , and V is velocity of the lithospheric plate. Oceanic lithosphere is less dense than asthenosphere for

2842-424: Is where they deal with nutrition and where their endosymbionts are found. They also have a bright red plume, which they use to uptake compounds such as O, H 2 S, and CO 2 , which feed the endosymbionts in their trophosome. Remarkably, the tubeworms hemoglobin (which incidentally is the reason for the bright red color of the plume) is capable of carrying oxygen without interference or inhibition from sulfide, despite

2940-729: The Atlantic and Pacific Oceans, at an average depth of 2,100 m (6,900 ft). The most northerly black smokers are a cluster of five named Loki's Castle , discovered in 2008 by scientists from the University of Bergen at 73°N , on the Mid-Atlantic Ridge between Greenland and Norway . These black smokers are of interest as they are in a more stable area of the Earth's crust, where tectonic forces are less and consequently fields of hydrothermal vents are less common. The world's deepest known black smokers are located in

3038-519: The Cayman Trough , 5,000 m (3.1 miles) below the ocean's surface. White smoker vents emit lighter-hued minerals, such as those containing barium , calcium and silicon . These vents also tend to have lower-temperature plumes probably because they are generally distant from their heat source. Black and white smokers may coexist in the same hydrothermal field, but they generally represent proximal (close) and distal (distant) vents to

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3136-657: The Figueroa Sulfide , from the Early Jurassic of California. The ecosystem so formed is reliant upon the continued existence of the hydrothermal vent field as the primary source of energy, which differs from most surface life on Earth, which is based on solar energy . However, although it is often said that these communities exist independently of the sun, some of the organisms are actually dependent upon oxygen produced by photosynthetic organisms, while others are anaerobic . The chemosynthetic bacteria grow into

3234-659: The Mid-Atlantic Ridge are extremely rich in metal content, such as Rainbow with 24,000  μM concentrations of iron . Black smokers were first discovered in 1979 on the East Pacific Rise by scientists from Scripps Institution of Oceanography during the RISE Project . They were observed using the deep submergence vehicle ALVIN from the Woods Hole Oceanographic Institution . Now, black smokers are known to exist in

3332-645: The Vaalbara supercontinent or the continent of Ur . There are two subregional geographical classification regimes used, being: The most important part of the Pilbara Craton to understand the early Earth crust is called the Eastern Pilbara Craton , where still exposed today, are crustal rocks that are up to 3.8 billion years old and intrusive granitic domes along with greenstone belts that are about 3.5 to 3.2 billion years old. The geology

3430-479: The earliest known life on land may have been found in 3.48-billion-year-old geyserite and other related mineral deposits (often found around hot springs and geysers ) uncovered in the Dresser Formation in the Pilbara Craton. Biogenic sedimentary structures (microbialites) such as stromatolites and MISS were described from tidal, lagoonal and subtidal coastal settings that can be reconstructed from

3528-533: The iron-sulfur world theory and suggested that life might have originated at hydrothermal vents. Wächtershäuser proposed that an early form of metabolism predated genetics. By metabolism he meant a cycle of chemical reactions that release energy in a form that can be harnessed by other processes. It has been proposed that amino acid synthesis could have occurred deep in the Earth's crust and that these amino acids were subsequently shot up along with hydrothermal fluids into cooler waters, where lower temperatures and

3626-517: The oldest forms of life on Earth . Putative fossilized microorganisms were discovered in hydrothermal vent precipitates in the Nuvvuagittuq Belt of Quebec, Canada , that may have lived as early as 4.280 billion years ago , not long after the oceans formed 4.4 billion years ago , and not long after the formation of the Earth 4.54 billion years ago. Hydrothermal vent ecosystems have enormous biomass and productivity, but this rests on

3724-506: The seabed , typically in the bathyal zone (with largest frequency in depths from 2,500 to 3,000 m (8,200 to 9,800 ft)), but also in lesser depths as well as deeper in the abyssal zone . They appear as black, chimney-like structures that emit a cloud of black material. Black smokers typically emit particles with high levels of sulfur-bearing minerals, or sulfides. Black smokers are formed in fields hundreds of meters wide when superheated water from below Earth's crust comes through

3822-520: The 3.47 billion year-old Mount Ada Basalt, a rock layer that is a few million years older than the Apex chert. However, the biogenicity of these supposed fossils has also been disputed, with some studies finding abiotic processes to be a more likely culprit for their formation. Additional potential bioindicators from the Precambrian have been found in the region, including carbonaceous microfossils in

3920-576: The Dresser stratigraphy as well. The rocks of the Dresser Formation display evidence of haematite alteration that may have been microbially influenced. The earliest direct evidence of life on Earth may be fossils of microorganisms permineralized in 3.465-billion-year-old Australian Apex chert rocks. However, the evidence for the biogenicity of these microstructures has been thoroughly debated. Originally, 11 taxa were described from

4018-765: The Fortescue and Hamersley basins is even younger, at less than 1.7 billion years old, as are the surrounding geo-ecosystems surface rocks to the Pilbara Craton. It is important to note that to the east and south of the Eastern Pilbara Craton there are significant outcrops of the very old rocks and that these are confined to the traditional area of the Pilbara Craton which is inferred to be subsurface for more than half its area. There are extensive high quality iron ore deposits and also economic to mine gold , silver , copper , nickel , lead , zinc , molybdenum , vanadium and fluorite deposits. Evidence of

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4116-639: The animal as opposed to inside the animal. Shrimp found at vents in the Mid-Atlantic Ridge were once thought of as an exception to the necessity of symbiosis for macroinvertebrate survival at vents. That changed in 1988 when they were discovered to carry episymbionts. Since then, other organisms at vents have been found to carry episymbionts as well, such as Lepetodrilis fucensis. Furthermore, while some symbionts reduce sulfur compounds, others are known as " methanotrophs " and reduce carbon compounds, namely methane. Bathmodiolid mussels are an example of

4214-416: The author describes as the unlikelihood of the formation of machinery which produces energy from the pH gradients found in hydrothermal vents without/before the existence of genetic information. This counterpoint has been responded to by Nick Lane , one of the researchers whose work it focuses on. He argues that the counterpoint largely misinterprets both his work and the work of others. Another reason that

4312-402: The bacteria living inside the worm. In return, the bacteria nourish the worm with carbon compounds. Two of the species that inhabit a hydrothermal vent are Tevnia jerichonana , and Riftia pachyptila . One discovered community, dubbed " Eel City ", consists predominantly of the eel Dysommina rugosa . Though eels are not uncommon, invertebrates typically dominate hydrothermal vents. Eel City

4410-518: The base of the black smoker, therefore completing the life cycle . A species of phototrophic bacterium has been found living near a black smoker off the coast of Mexico at a depth of 2,500 m (8,200 ft). No sunlight penetrates that far into the waters. Instead, the bacteria, part of the Chlorobiaceae family, use the faint glow from the black smoker for photosynthesis . This is the first organism discovered in nature to exclusively use

4508-520: The bulk of nonmicrobial organisms. Siboglinid tube worms , which may grow to over 2 m (6.6 ft) tall in the largest species, often form an important part of the community around a hydrothermal vent. They have no mouth or digestive tract, and like parasitic worms, absorb nutrients produced by the bacteria in their tissues. About 285 billion bacteria are found per ounce of tubeworm tissue. Tubeworms have red plumes which contain hemoglobin . Hemoglobin combines with hydrogen sulfide and transfers it to

4606-407: The centers of entire ecosystems . Sunlight is nonexistent, so many organisms, such as archaea and extremophiles , convert the heat, methane , and sulfur compounds provided by black smokers into energy through a process called chemosynthesis . More complex life forms, such as clams and tubeworms , feed on these organisms. The organisms at the base of the food chain also deposit minerals into

4704-451: The chemoautotrophic bacteria at hydrothermal vents might be responsible for contributing to the diet of suspension-feeding bivalves. Finally, in 1981, it was understood that giant tubeworm nutrition acquisition occurred as a result of chemoautotrophic bacterial endosymbionts. As scientists continued to study life at hydrothermal vents, it was understood that symbiotic relationships between chemoautotrophs and macrofauna invertebrate species

4802-449: The deep-sea hydrothermal vents could continue for millennia (until the oxygen was depleted). The chemical and thermal dynamics in hydrothermal vents makes such environments highly suitable thermodynamically for chemical evolution processes to take place. Therefore, thermal energy flux is a permanent agent and is hypothesized to have contributed to the evolution of the planet, including prebiotic chemistry. Günter Wächtershäuser proposed

4900-432: The depth to the isotherm associated with the transition between brittle and viscous behavior. The temperature at which olivine becomes ductile (~1,000 °C or 1,830 °F) is often used to set this isotherm because olivine is generally the weakest mineral in the upper mantle. The lithosphere is subdivided horizontally into tectonic plates , which often include terranes accreted from other plates. The concept of

4998-399: The dissolved CO 2 in the water. Additionally, the discovery of supercritical CO 2 at some sites has been used to further support the theory of hydrothermal origin of life given that it can increase organic reaction rates. Its high solvation power and diffusion rate allow it to promote amino and formic acid synthesis, as well as the synthesis of other organic compounds, polymers, and

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5096-552: The early 21st century posit that large pieces of the lithosphere have been subducted into the mantle as deep as 2,900 kilometres (1,800 mi) to near the core-mantle boundary, while others "float" in the upper mantle. Yet others stick down into the mantle as far as 400 kilometres (250 mi) but remain "attached" to the continental plate above, similar to the extent of the old concept of "tectosphere" revisited by Jordan in 1988. Subducting lithosphere remains rigid (as demonstrated by deep earthquakes along Wadati–Benioff zone ) to

5194-463: The environment. Organisms living at the edge of hydrothermal vent fields, such as pectinid scallops, also carry endosymbionts in their gills, and as a result their bacterial density is low relative to organisms living nearer to the vent. However, the scallop's dependence on the microbial endosymbiont for obtaining their nutrition is therefore also lessened. Furthermore, not all host animals have endosymbionts; some have episymbionts—symbionts living on

5292-504: The fact that oxygen and sulfide are typically very reactive. In 2005, it was discovered that this is possible due to zinc ions that bind the hydrogen sulfide in the tubeworms hemoglobin, therefore preventing the sulfide from reacting with the oxygen. It also reduces the tubeworms tissue from exposure to the sulfide and provides the bacteria with the sulfide to perform chemoautotrophy. It has also been discovered that tubeworms can metabolize CO 2 in two different ways, and can alternate between

5390-403: The filaments has also been repeatedly examined with Raman spectroscopy which has yielded mixed interpretations of results and is therefore regarded by many to be unreliable for determining biogenicity when used alone. Perhaps the most compelling argument to date is based on high spatial resolution electron microscopy like scanning and transmission electron microscopy . This study concludes that

5488-601: The formation of colloids and nanoparticles can keep these redox-sensitive elements suspended in solution far from the vent site. Fe and Mn often have the highest concentrations among metals in acidic hydrothermal vent fluids, and both have biological significance, particularly Fe, which is often a limiting nutrient in marine environments. Therefore, far-field transport of Fe and Mn via organic complexation may constitute an important mechanism of ocean metal cycling. Additionally, hydrothermal vents deliver significant concentrations of other biologically important trace metals to

5586-541: The formation of early cells. Meanwhile, proponents of the deep sea hydrothermal vent hypothesis suggest thermophoresis in mineral cavities to be an alternative compartment for polymerization of biopolymers. How thermophoresis within mineral cavities could promote coding and metabolism is unknown. Nick Lane suggests that nucleotide polymerization at high concentrations of nucleotides within self-replicating protocells, where "Molecular crowding and phosphorylation in such confined, high-energy protocells could potentially promote

5684-479: The formation of these organic molecules . However, the origin of life is a widely debated topic, and there are many conflicting viewpoints. Hydrothermal vents in the deep ocean typically form along the mid-ocean ridges , such as the East Pacific Rise and the Mid-Atlantic Ridge . These are locations where two tectonic plates are diverging and new crust is being formed. The water that issues from seafloor hydrothermal vents consists mostly of seawater drawn into

5782-403: The four amino acids: alanine, arginine, aspartic acid, and glycine. In situ experiments have revealed the convergence of high N 2 content and supercritical CO 2 at some sites, as well as evidence for complex organic material (amino acids) within supercritical CO 2 bubbles. Proponents of this theory for the origin of life also propose the presence of supercritical CO 2 as a solution to

5880-401: The global ocean at active vent sites creates hydrothermal plumes. Hydrothermal deposits are rocks and mineral ore deposits formed by the action of hydrothermal vents. Hydrothermal vents exist because the Earth is both geologically active and has large amounts of water on its surface and within its crust. Under the sea, they may form features called black smokers or white smokers, which deliver

5978-414: The host provides the symbiont with chemicals required for chemosynthesis, such as carbon, sulfide, and oxygen. In the early stages of studying life at hydrothermal vents, there were differing theories regarding the mechanisms by which multicellular organisms were able to acquire nutrients from these environments, and how they were able to survive in such extreme conditions. In 1977, it was hypothesized that

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6076-461: The hydrothermal plume and surrounding seawater generate turbulent flow that facilitates mixing between the two types of fluids, which progressively dilutes the hydrothermal plume with seawater. Eventually, the coupled effects of dilution and rising into progressively warmer (less dense) overlying seawater will cause the hydrothermal plume to become neutrally buoyant at some height above the seafloor; therefore, this stage of hydrothermal plume evolution

6174-695: The hydrothermal plume will eventually oxidize to form insoluble Fe and Mn (oxy)hydroxide minerals . For this reason, the hydrothermal "near field" has been proposed to refer to the hydrothermal plume region undergoing active oxidation of metals while the term "far field" refers to the plume region within which complete metal oxidation has occurred. Several chemical tracers found in hydrothermal plumes are used to locate deep-sea hydrothermal vents during discovery cruises. Useful tracers of hydrothermal activity should be chemically unreactive so that changes in tracer concentration subsequent to venting are due solely to dilution. The noble gas helium fits this criterion and

6272-515: The hydrothermal system close to the volcanic edifice through faults and porous sediments or volcanic strata, plus some magmatic water released by the upwelling magma . In terrestrial hydrothermal systems, the majority of water circulated within the fumarole and geyser systems, is meteoric water plus ground water that has percolated down into the thermal system from the surface, but also commonly contains some portion of metamorphic water , magmatic water , and sedimentary formational brine that

6370-418: The lack of phospholipid bilayer membranes and proton pumps in early organisms, allowing ion gradients to form despite the lack of cellular machinery and components present in modern cells. There is some discourse around this topic. It has been argued that the natural pH gradients of these vents playing a role in the origin of life is actually implausible. The counter argument relies, among other points, on what

6468-564: The lithosphere as Earth's strong outer layer was described by the English mathematician A. E. H. Love in his 1911 monograph "Some problems of Geodynamics" and further developed by the American geologist Joseph Barrell , who wrote a series of papers about the concept and introduced the term "lithosphere". The concept was based on the presence of significant gravity anomalies over continental crust, from which he inferred that there must exist

6566-572: The main upflow zone, respectively. However, white smokers correspond mostly to waning stages of such hydrothermal fields, as magmatic heat sources become progressively more distant from the source (due to magma crystallization) and hydrothermal fluids become dominated by seawater instead of magmatic water. Mineralizing fluids from this type of vent are rich in calcium and they form dominantly sulfate -rich (i.e., barite and anhydrite ) and carbonate deposits. Hydrothermal plumes are fluid entities that manifest where hydrothermal fluids are expelled into

6664-543: The mantle flow that accompanies plate tectonics. The upper part of the lithosphere is a large habitat for microorganisms , with some found more than 4.8 km (3 mi) below Earth's surface. Hydrothermal vent Hydrothermal vents are fissures on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges , ocean basins, and hotspots . The dispersal of hydrothermal fluids throughout

6762-421: The mantle lithosphere there is thicker and less dense than typical; the relatively low density of such mantle "roots of cratons" helps to stabilize these regions. Because of its relatively low density, continental lithosphere that arrives at a subduction zone cannot subduct much further than about 100 km (62 mi) before resurfacing. As a result, continental lithosphere is not recycled at subduction zones

6860-416: The mantle part of the oceanic lithosphere can be approximated as a thermal boundary layer that thickens as the square root of time. h ∼ 2 κ t {\displaystyle h\,\sim \,2\,{\sqrt {\kappa t}}} Here, h {\displaystyle h} is the thickness of the oceanic mantle lithosphere, κ {\displaystyle \kappa }

6958-406: The mid-ocean ridge. The oldest oceanic lithosphere is typically about 140 kilometres (87 mi) thick. This thickening occurs by conductive cooling, which converts hot asthenosphere into lithospheric mantle and causes the oceanic lithosphere to become increasingly thick and dense with age. In fact, oceanic lithosphere is a thermal boundary layer for the convection in the mantle. The thickness of

7056-481: The minerals precipitate out to form particles which add to the height of the stacks. Some of these chimney structures can reach heights of 60 m (200 ft). An example of such a towering vent was "Godzilla", a structure on the Pacific Ocean deep seafloor near Oregon that rose to 40 m (130 ft) before it fell over in 1996. A black smoker or deep-sea vent is a type of hydrothermal vent found on

7154-448: The nano-scale morphology of the filaments and the distribution of the carbonaceous matter are inconsistent with a biological origin for the filaments. Instead, it is more likely that the hydrothermal conditions have assisted in the heating, hydration and exfoliation of potassium micas on which barium, iron and carbonate have secondarily been adsorbed. Carbonaceous structures appearing to be of biological origin have also been discovered in

7252-414: The northeastern Pilbara Craton. Continental lithosphere Earth's lithosphere, which constitutes the hard and rigid outer vertical layer of the Earth, includes the crust and the lithospheric mantle (or mantle lithosphere), the uppermost part of the mantle that is not convecting. The lithosphere is underlain by the asthenosphere which is the weaker, hotter, and deeper part of the upper mantle that

7350-474: The ocean floor (water may attain temperatures above 400 °C (752 °F)). This water is rich in dissolved minerals from the crust, most notably sulfides . When it comes in contact with cold ocean water, many minerals precipitate, forming a black, chimney-like structure around each vent. The deposited metal sulfides can become massive sulfide ore deposits in time. Some black smokers on the Azores portion of

7448-524: The ocean such as Mo, which may have been important in the early chemical evolution of the Earth's oceans and to the origin of life (see "theory of hydrothermal origin of life"). However, Fe and Mn precipitates can also influence ocean biogeochemistry by removing trace metals from the water column. The charged surfaces of iron (oxy)hydroxide minerals effectively adsorb elements such as phosphorus , vanadium , arsenic , and rare earth metals from seawater; therefore, although hydrothermal plumes may represent

7546-466: The ocean. Hydrothermal vent fluids harbor temperatures (~40 to >400 °C) well above that of ocean floor seawater (~4 °C), meaning that hydrothermal fluid is less dense than the surrounding seawater and will rise through the water column due to buoyancy , forming a hydrothermal plume; therefore, the phase during which hydrothermal plumes rise through the water column is known as the "buoyant plume" phase. During this phase, shear forces between

7644-422: The order of 30 cm (1 ft) per day have been recorded. An April 2007 exploration of the deep-sea vents off the coast of Fiji found those vents to be a significant source of dissolved iron (see iron cycle ). Some hydrothermal vents form roughly cylindrical chimney structures. These form from minerals that are dissolved in the vent fluid. When the superheated water contacts the near-freezing sea water,

7742-557: The overlying water column at active hydrothermal vent sites. As hydrothermal fluids typically harbor physical (e.g., temperature , density ) and chemical (e.g., pH , Eh , major ions) properties distinct from seawater , hydrothermal plumes embody physical and chemical gradients that promote several types of chemical reactions, including oxidation-reduction reactions and precipitation reactions . Because of these reactions, hydrothermal plumes are dynamic entities whose physical and chemical properties evolve over both space and time within

7840-432: The overriding lithosphere, which can be oceanic or continental. New oceanic lithosphere is constantly being produced at mid-ocean ridges and is recycled back to the mantle at subduction zones. As a result, oceanic lithosphere is much younger than continental lithosphere: the oldest oceanic lithosphere is about 170 million years old, while parts of the continental lithosphere are billions of years old. Geophysical studies in

7938-489: The polymerization of nucleotides to form RNA". Acetyl phosphate could possibly promote polymerization at mineral surfaces or at low water activity. A computational simulation shows that nucleotide concentration of nucleotide catalysis of "the energy currency pathway is favored, as energy is limiting; favoring this pathway feeds forward into a greater nucleotide synthesis". Fast nucleotide catalysis of CO 2 fixation lowers nucleotide concentration as protocell growth and division

8036-481: The presence of clay minerals would have fostered the formation of peptides and protocells . This is an attractive hypothesis because of the abundance of CH 4 ( methane ) and NH 3 ( ammonia ) present in hydrothermal vent regions, a condition that was not provided by the Earth's primitive atmosphere. A major limitation to this hypothesis is the lack of stability of organic molecules at high temperatures, but some have suggested that life would have originated outside of

8134-462: The presence of supercritical CO 2 in Hadean hydrothermal vents played an important role in the origin of life. There is some evidence that links the origin of life to alkaline hydrothermal vents in particular. The pH conditions of these vents may have made them more suitable for emerging life. One current theory is that the naturally occurring proton gradients at these deep sea vents supplemented

8232-687: The reactions are capable of phosphorylating ADP to ATP, with maximum synthesis occurring at high water activity and low concentrations of ions, the Hadean ocean likely had lower concentrations of ions than modern oceans. The concentrations of Mg and Ca at alkaline hydrothermal systems are lower than the at the ocean. The high concentration of potassium within most life forms could be readily explained that protocells might have evolved sodium-hydrogen antiporters to pump out Na as prebiotic lipid membranes are less permeable to Na than H . If cells originated at these environments, they would have been autotrophs with

8330-471: The structure of its dermal sclerites (hardened body parts), instead of calcium carbonate . The extreme pressure of 2,500 m of water (approximately 25  megapascals or 250  atmospheres ) is thought to play a role in stabilizing iron sulfide for biological purposes. This armor plating probably serves as a defense against the venomous radula (teeth) of predatory snails in that community. In March 2017, researchers reported evidence of possibly

8428-541: The sun to perform photosynthesis. Instead, the microbial life found at hydrothermal vents is chemosynthetic; they fix carbon by using energy from chemicals such as sulfide, as opposed to light energy from the sun. In other words, the symbiont converts inorganic molecules (H 2 S, CO 2 , O) to organic molecules that the host then uses as nutrition. However, sulfide is an extremely toxic substance to most life on Earth. For this reason, scientists were astounded when they first found hydrothermal vents teeming with life in 1977. What

8526-420: The sun. Some hydrothermal vent organisms do consume this "rain", but with only such a system, life forms would be sparse. Compared to the surrounding sea floor, however, hydrothermal vent zones have a density of organisms 10,000 to 100,000 times greater. These organisms include yeti crabs , which have long hairy arms that they reach out over the vent to collect food with. The hydrothermal vents are recognized as

8624-415: The symbiotic relationships that have evolved at vents. Deep-sea hydrothermal vent ecosystems differ from their shallow-water and terrestrial hydrothermal counterparts due to the symbiosis that occurs between macroinvertebrate hosts and chemoautotrophic microbial symbionts in the former. Since sunlight does not reach deep-sea hydrothermal vents, organisms in deep-sea hydrothermal vents cannot obtain energy from

8722-519: The two as needed as environmental conditions change. In 1988, research confirmed thiotrophic (sulfide-oxidizing) bacteria in Alviniconcha hessleri , a large vent mollusk. In order to circumvent the toxicity of sulfide, mussels first convert it to thiosulfate before carrying it over to the symbionts. In the case of motile organisms such as alvinocarid shrimp, they must track oxic (oxygen-rich) / anoxic (oxygen-poor) environments as they fluctuate in

8820-489: The view of deep sea hydrothermal vents as an ideal environment for the origin of life remains controversial is the absence of wet-dry cycles and exposure to UV light, which promote the formation of membranous vesicles and synthesis of many biomolecules. The ionic concentrations of hydrothermal vents differs from the intracellular fluid within the majority of life. It has instead been suggested that terrestrial freshwater environments are more likely to be an ideal environment for

8918-578: The way oceanic lithosphere is recycled. Instead, continental lithosphere is a nearly permanent feature of the Earth. Geoscientists can directly study the nature of the subcontinental mantle by examining mantle xenoliths brought up in kimberlite , lamproite , and other volcanic pipes . The histories of these xenoliths have been investigated by many methods, including analyses of abundances of isotopes of osmium and rhenium . Such studies have confirmed that mantle lithospheres below some cratons have persisted for periods in excess of 3 billion years, despite

9016-488: The zones of highest temperature. There are numerous species of extremophiles and other organisms currently living immediately around deep-sea vents, suggesting that this is indeed a possible scenario. Experimental research and computer modeling indicate that the surfaces of mineral particles inside hydrothermal vents have similar catalytic properties to enzymes and are able to create simple organic molecules, such as methanol (CH 3 OH) and formic acid (HCO 2 H), out of

9114-472: The “water paradox” that pervades theories on the origin of life in aquatic settings. This paradox encompasses the fact that water is both required for life and will, in abundance, hydrolyze organic molecules and prevent dehydration synthesis reactions necessary to chemical and biological evolution. Supercritical CO 2 , being hydrophobic, acts as a solvent that facilitates an environment conducive to dehydration synthesis. Therefore, it has been hypothesized that

9212-405: Was a single biogeographic vent region found in the eastern Pacific. The subsequent barrier to travel began the evolutionary divergence of species in different locations. The examples of convergent evolution seen between distinct hydrothermal vents is seen as major support for the theory of natural selection and of evolution as a whole. Although life is very sparse at these depths, black smokers are

9310-548: Was discovered was the ubiquitous symbiosis of chemoautotrophs living in ( endosymbiosis ) the vent animals' gills; the reason why multicellular life is capable to survive the toxicity of vent systems. Scientists are therefore now studying how the microbial symbionts aid in sulfide detoxification (therefore allowing the host to survive the otherwise toxic conditions). Work on microbiome function shows that host-associated microbiomes are also important in host development, nutrition, defense against predators, and detoxification. In return,

9408-605: Was not found to be supercritical but a brief injection of 464 °C (867 °F) was well above supercritical conditions. A nearby site, Turtle Pits, was found to vent low salinity fluid at 407 °C (765 °F), which is above the critical point of the fluid at that salinity. A vent site in the Cayman Trough named Beebe , which is the world's deepest known hydrothermal site at ~5,000 m (16,000 ft) below sea level, has shown sustained supercritical venting at 401 °C (754 °F) and 2.3 wt% NaCl. Although supercritical conditions have been observed at several sites, it

9506-411: Was reassessed in 2007 with the separation out from the geologically named Pilbara Craton of a thick succession of interbedded clastic or chemical sedimentary rocks and volcanic rocks forming the Fortescue, Hamersley, and Turee Creek basins that are usually aged from 2.78–2.42 billion years old and the younger volcano-sedimentary Ashburton Basin aged from 2.21–1.79 billion years ago. A surface region between

9604-409: Was ubiquitous. For instance, in 1983, clam gill tissue was confirmed to contain bacterial endosymbionts; in 1984 vent bathymodiolid mussels and vesicomyid clams were also found to carry endosymbionts. However, the mechanisms by which organisms acquire their symbionts differ, as do the metabolic relationships. For instance, tubeworms have no mouth and no gut, but they do have a "trophosome", which

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