224IG Final Study Guide (PDF)

Lecture 13 3 ways to melt the mantle: 3 kinds of volcanoes 1.reuce pressure without losing heat=MORB volcanism -the melting of the mantle can occur when pressure is reduced while maintaining heat. This process typically happens at mid ocean ridges, where tectonic plates are moving apart. As the...

Lecture 13 3 ways to melt the mantle: 3 kinds of volcanoes 1.reuce pressure without losing heat=MORB volcanism -the melting of the mantle can occur when pressure is reduced while maintaining heat. This process typically happens at mid ocean ridges, where tectonic plates are moving apart. As the mantle rises to fill the gap, the decrease in pressure allows the solid mantle material to melt, forming magma. This process results in the formation of basaltic lava, known as mid ocean ridge basalts. 2\. add water-recues melting temperature= subduction volcanoes -when oceanic plates subduct beneath continental plates, water trapped in sediments and minerals is released into the mantle. The addition of water lowers the melting temperature of the mantle material, allowing it to melt more easily. This process generates magma that rises to form volcanoes associated with subduction zones, such as the cascades in the pacific northwest. 3.increase temperature- hotspots volcanoes -hotspot volcanism occurs when a plume of hot mantle material rises toward the surface, increasing the temperature of the surrounding rock. This can happen at locations not necessarily associated with plate boundaries. As the temperatures increases, it can melt the mantle, creating magma. Examples include the Hawaiian Islands, which formed over a stationary hotpot. key points: ways to melt mantle are to reduce pressure, add water, or increase temperature. [MORB melting by adiabatic decompression] -plate spreads Tectonic plates pull apart at mid ocean ridges -mantle upwells As the plate separate, material from the mantle rises to fill the gap -when the mantle upwells, pressure decreases. But the rock still has the same heat and essentially the same temperature, but still a bit cooler When the mantle rock rises, the pressure on it decreases. Although the rock is still hot, it cools slightly due to the lower pressure -therefore the upwelling mantle rock melts Because the pressure drops but the heat remains mostly the same, the upwelling mantle rock begins to melt, forming magma -adiabatic decompression means lowering the pressure without loosing heat -reduce the pressure, but keep the heat constant=mantle melts By reducing the pressure while keeping the heat constant, the mantle rock melts, creating magma that can lead to volcanic activity -the solidus is the temperature at which the first tiny but of melt (magma) starts to form in the rock A diagram of a diagram of a solidus Description automatically generated with medium confidence Mantle melting process: 1.lower the pressure: -as the mantle rises, the temperature decreases. This causes the volume to increase and the temperature cools slightly, but the overall heat content stays about the same. 2\. adiabatic rise: -when the mantle rises without losing heat, it undergoes what is called adiabatic rise. This means it expands as it moves upward without transferring heat to its surroundings. 3\. decompression partial melting: -as the mantle rises and pressure drops, some of the rock can rapidly melt. This process can potentially melt up to 30% of the mantle rock. MORB volcanism:  key terms: [geotherm]: a line that shows the temperature of the mantle at different depths in the earth. It helps to understand how temperature changes with depth. [Solidus]: this line represents the temperature at which the first small amount of melt (magma) starts to form in the rock. Below this temperature the rock is completely solid. [Liquidus]: this line indicates the temperature at which the rock is completely melted into magma (100% liquid). Above this temperature, the rock is fully molten. [Adiabat]: the path that a piece of mantle rock follows in pressure temperature (P-T) space as it rises without loosing heat. It describes the changes in pressure and temperature that occur during adiabatic rise. The solidus is where melting begins, the liquids is where everything is melted and the geotherm shows the temperature changes with depth. The adiabat describes the path of rising mantle without heat loss 2)subduction volcanoes :\ -water lowers the solidus temperature of mantle rock, allowing it to melt at lower temperatures. This process is crucial for magma generation, especially in subduction zones. A diagram of different types of soil Description automatically generated 3\) mantle plumes  A diagram of a volcano Description automatically generated What happens to the stuff that subducts? 1.compostion of the ocean floor: -the ocean floor primarily consists of basalt, which is formed from volcanic eruptions at mid ocean ridges. The basalt is transported long distance by the movement of tectonic plates. 2\. weathering of continental crust -the continental crust weathers over time, breaking down into silts and clays. These sediments are carried by rivers and streams into the oceans, where they settle and form a thin layer (veneer) on the ocean floor. 3\. subduction process: -at subduction zones, the oceanic crust and the sediment veneer are pushed down into the mantle as one tectonic plate slides beneath another. This process involves the oceanic plate bending and descending into the earth. What happens next?\ -once materials are subducted into the mantle, they can undergo various transformations. [Metamorphism]: the increased temperature and pressure can change the mineral composition of the subducted materials. [Melting]: some of the subducted oceanic crust and sediment can melt. Contributing to the formation of magma. This magma can eventually rise back to the surface, leading to volcanic activity. [Recycling]: the materials may be recycled back into the mantle or contribute to the formation of new crust in volcanic arcs associated with subduction zones. Do we ever see it again? -while the exact materials may not return to the surface unchanged, the processes of metamorphism and melting can lead to the formation of new igneous rocks and minerals that can be erupted in volcanic activity. So elements and compounds from the subducted oceanic crust and sediments can reappear in new forms, such as volcanic rock.  Clues from 10Be what is 10Be: -10Be is a radioactive isotope that has a half life of about 1.39 million years. It is produced in the upper atmosphere when cosmic rays interact with nitrogen and oxygen. Formation process: -like 14C is created, 10Be is produced via a process called cosmic ray spallation. After its formation, 10BE settles out of the atmosphere and eventually enters the oceans, where it accumulates in marine sediments. Subduction process: -when marine sediments containing live(radioactive) 10Be are subducted at tectonic plate boundaries, they move down into the mantle. Presence in subduction zone lavas: -the question arises: is there live 10Be in lavas produced in subduction zones? -if 10Be is found in volcanic rocks from these zones, it means that the subducted sediments still contain detectable levels of this isotope. What does it tell us?\ if we find live 10Be in subduction zone lavas, it suggests that: -sediments are not fully transformed: the presence of 10Be indicates that the subducted materials have not been entirely melted or altered during their descent into the mantle. -timeframe of subduction: since 10Be has a half life of 1.39 million years, its presence indicates that the sediment was relatively recently subducted in geological terms. This can help researches understand the age of the materials being subducted and the dynamics of the subduction process. -connection to surface processes: these findings can provide insights into how surface processes like erosion and sedimentation are connected to volcanic activity and mantle dynamics. The fate of subducted stuff: the mantle recycles Types of basalt: -MORB: mid ocean ridge basalt, formed at mid ocean ridges. -OIB: ocean island basalt, formed at hotspots, often far from tectonic plate boundaries like Hawaii. -IAB: island arc basalt, formed at volcanic arcs near subduction zones Recycling process: MORB formation: -at mid ocean ridges, the mantle undergoes passive upwelling due to tectonic plates pulling apart. This upwelling allows the mantle to melt and form MORB, which creates new oceanic crust. IAB formation: -as an oceanic plate subducts beneath another plate, it creates tension that pulls on the rest of the plate. The portion of the subducting plate that is heated can partially melt, leading to the formation of island arc volcanoes that erupt IAB. These volcanoes are typically found along the edges of tectonic plates. OIB formation: -after the subducted plate sinks into the mantle, it heats up and may eventually rise again as a mantle plume. This plume can rise though the mantle and impinge on the base of tectonic plates, causing them to melt and form OIB. Hotspot volcanism, such as that found in Hawaii is an example of this process. A diagram of a sea Description automatically generated How to trace subducted material through this mess?\ distinct isotopic fingerprints: -isotopes are variants of elements that have different numbers of neutrons. Subducted continental crust has a unique isotopic ratios that can serve as fingerprints. -by analyzing the isotopic composition of volcanic rocks or sediments that originate from subduction zones, researches can identify whether these materials came from subducted continental crust. Each type of crust has its own isotopic signature based on its formation and history. Distance trace element ratios -trace elements present in very small amounts in rocks but can reveal important information about their source. Subducted continental crust has specific ratios of trace elements that differ from those found in oceanic crust or mantle material. -by measuring these trace element ratios in volcanic rocks produced at subduction zones, scientists can distinguish between materials derived from subducted oceanic crust vs subducted continental crust. For instance, elements like Ba, Sr, Pb can indicate contributions from continental crust.  A graph with lines and dots Description automatically generated with medium confidence  A graph of a number of objects Description automatically generated with medium confidence  A diagram of a pyramid Description automatically generated [Lecture 14 ] How did the continents form? 1.collision of island arcs -when oceanic crust subducts beneath another oceanic crust, it creates island arc volcanoes. -over time, these island arcs can collide with the edges of existing continents or with each other, adding their volcanic material to the growing continents. -these collision gradually built up and enlarged the continents over millions of years. 2.subduction of oceanic crust beneath continental crust -when an oceanic plate is forced beneath a continental plate, the oceanic crust melts as it sinks into the mantle. -the melting generates magma, which rises to form volcanoes along the edges of the continent. -this volcanic material contributes to the growth of continents along their margins.  1.Adding water to mantel peridotite: -in subduction zones, water from the subducting plate is introduced into the mantle. This lowers the melting point of mantle peridotite and produces a melt that has a higher silica concentration. -water promotes the melting of minerals in the mantle that are silica rich, leading to the production of andesitic to granitic melts, which are rich in SiO2 -the volcanic lavas erupted at subduction zones tend to be silica rich and have composition ranging from andesite to granite. These lavas contribute to the formation of continental crust. 2\. melting dry mantle peridotite -at mid ocean ridges, there is no water to help the mantle melt. Instead the mantle melts by decompressing melting (adiabatic decompression) and the resulting melt in lower silica. -without water, the melting process produces basaltic magmas, which are naturally lower in silica. -the volcanic lavas erupted at mid ocean ridges, are basaltic and have lower silica concentrations compared to subduction zone lavas. ------------- ------------------ ------------------ ------------- **Process** **Type of Melt** **SiO₂ Content** **Example** ------------- ------------------ ------------------ ------------- ------------------------------- ----------------------- ----------- ----------------------- **Water + Mantle Peridotite** Andesitic to granitic High SiO₂ Subduction zone lavas ------------------------------- ----------------------- ----------- ----------------------- **Dry Mantle Peridotite** Basaltic (MORB) Low SiO₂ Mid-ocean ridge lavas --------------------------- ----------------- ---------- ----------------------- Summary: -subduction zones: water rich environments produce SiO2 rich andesitic to granitic melts, leading to the formation of continental crust. -mid ocean ridges: dry mantle melts produce SiO2 poor basaltic melts, forming oceanic crust. First piece of evidence that continental formation required subduction: major elements A diagram of different colors Description automatically generated peridotite is a mantle source rock low in silica and alkali content. -their composition is typical of dry mantle melting which forms basaltic magmas. Basalts are derived from melting dry mantle peridotite, have a higher silica that peridotite but are still low. -they're low in alkalis Andesitic magmas form in subduction zones where water is added to the mantle. This increases silica content. -they're moderate in alkalis, reflecting contributions from subducted materials. Rhyolite: they're highly evolved, silica rich rocks with the highest Na2O+K2O content. -these rocks form in water rich environment and result from extensive fractional crystallization or crustal melting. Dry conditions: peridotite to basalt -melts are produced at mid ocean ridges by dry decompression melting of the mantle. Leading to basaltic compositions. -these are low in SiO2 and alkalis, characteristics of oceanic crust. Wet conditions: andesite to rhyolite -in subduction zones, water from subducted plates lowers the mantle's solidus temperature. This results in silica and alkali melts that form andesites and with further evolution, rhyolites. -these compositions are associated with continental crust formation. 2^nd^ piece of evidence that continents formed by subduction zone melting: trace elements Trace element behavior especially the depletion of Ti, Ta, Nb (referred to as TITAN elements), provides strong evidence that continental crust formed through subduction processes. Subduction zone lavas TITAN elements are depleted: -lavas from subduction zones show lower concentrations of Ti, Ta, Nb compared to other types of volcanic rocks. -these elements are known as high field strength elements (HFSE) because of their resistance to being mobilized during subduction process. Why are titan elements depleted? -rutile (TiO2) is a stable mineral in subducting oceanic crust, rutile holds onto Ti, Ta, Nb as the slab undergoes dehydration and melting. -during subduction, fluids and melts are released from the slab, carrying away other incompatible elements. However, TITAN elements are retained in rutile and remain with the subducted slab. Subducted lavas and continental crust Continental crust also shows TITAN depletion -like subduction zone lavas, the bulk continental crust is also depleted in Ti, Ta, Nb. -this depletion is a key fingerprint linking continental crust formation to subduction processes. -since TITAN depletion is a characteristic of subduction zone lavas and the continental crust, it suggests that continents were formed through similar mechanisms. \--partial melting of the subduction slab releases silica rich magmas while retaining TITAN elements in the solid residue, like rutile -these magmas rise to form andesitic to granitic rocks, which contribute to the growth of continents. -rutile's role: this mineral locks up TITAN elements during subduction. Leaving them absent in the melts that eventually build continental crust. how quickly did the continents grow? -continental formation began over 4 billion years ago, with rapid growth during the Archean eon. Most of the present day continents were in place by 2.5 billion years ago, with steady additions and recycling occurring since then. Mixing The society islands, part of the EMI(enriched mantle II) geochemical signature, provide evidence for the contribution of continental crust material to mantle plumes. This conclusion is supported by elemental and isotopic evidence and is linked to the mixing of subducted crustal material with the mantle. Mantle samples and peridotites:\ peridotites: these ultramafic rock, rich in olivine represent the dominant composition of the earths mantle. Lherzolite: a type of peridotite that contains a mix of olivine, orthopyroxene and clinopyroxene, it's a common mantle rock and often serves as a baseline for mantle geochemistry. -the enriched mantle II reservoir shows geochemical evidence of having been influenced by crustal material, especially subducted sediment and continental curst. -EMII is characterized by distinct trace element ratios and isotopic signatures that differ from other mantle reservoirs like MORB or HMU (high U/Pb) Trace elements: -elevated concentrations of elements like Rb, Ba, and Pb which are enriched in continental crust compared to mantle peridotite. -depletions in high field strength elements (HFSEs) like Nb and Ta, consistent with. Subduction processes. -radiogenic isotope ratios like Sr, Nd, Pb in society island lavas point to mixing between primitive mantle material and recycled continental crust. -the presence of continental crust material in plume derived lavas suggests that subduction zones introduced sediments and altered oceanic crust in the mantle -over geological timescales, these subducted materials are transported into the deep mantle and later contribute to upwelling plumes. The geochemical signatures observed in the society islands reveal a memory of subducted continental crust materials. This evidence supports the idea that mantle plumes, like those responsible for the society islands are not composed of purely primitive mantle material but instead represent a mixture of :\ -peridotitic mantle material -recycled crustal components: including subducted sediments and altered oceanic crust  Mixing seawater (conserve mass)  **FA​:** The mass fraction of seawater in the mixture.  **FB:** the mass fraction of freshwater in the mixture When mixing, the total mass of seawater and freshwater equals the total mass of the mixture. FA​+FB​=1 This means that if FA is known, FB can be calculated as: FB​=1−FA​ Mixing sweater and freshwater: -seawater (FA): contains salt -freshwater (FB): has little to no salt -the mixtures mass fraction of each component is determined by the proportions added. -the salt content in the mixture is directly proportional to FA, because freshwater does not contributed to salinity -the mixture will have properties intermediate between seawater and freshwater based on the relative amounts of FA and FB. Mixing Sr in seawater -when mixing seawater and freshwater, the concertation of Sr in the resulting mixture depends on the mass of the two components and their initial concentrations. -CA: concertation of Sr in sweater -CB: concertation of Sr in freshwater \--typically, CB is around 0 since freshwater has negligible Sr -CA+B: concertation of Sr in the mixture -FA: mass fraction of sweater in the mixture -FB: mass fraction of freshwater in the mixture \-\--FB=1-FA The concentration of Sr in the mixture is calculated by mass conservation: CA+B​=FA​⋅CA​+FB​⋅CB​ Since FB=1-FA, this can also be written as: CA+B=FA\*CA+(1-FA) \*CB Example: CA=10 ppm (Sr concentration in seawater) CB=1 ppm (Sr concertation in freshwater) FA=1 (mass fraction of seawater) FB=0 (mass fraction of freshwater) CA+B=FA\*CA+FB\*CB CA+B=(1\*10)+(0\*1)=10 ppm Sr A black line with black text Description automatically generated Example: CA=10 ppm Sr CB=1 ppm Sr FA=0 (mass fraction of seawater) FB= 1 (mass fraction of freshwater) CA+B=FA\*CA+FB\*CB CA+B=(0\*10)+(1\*1)=1 ppm Sr  Example: CA=10 ppm Sr CB=1 ppm Sr FA= 0.5 FB=0.5 CA+B=FA\*CA+FB\*CB CA+B=(0.5\*10)+(0.5\*1)=5.5 ppm Sr A diagram of a graph Description automatically generated Mixing Sr isotopes in seawater To calculate the Sr isotope ratio of a mixture of seawater and freshwater, the following formula applies IA+B​=(FA​⋅CA​+IA)+(FB​⋅CB​\*IB)/(FA\*CA)+(FB\*CB) IA: Sr isotope ratio in seawater IB: Sr isotope ratio in freshwater IA+B: Sr isotope ratio of the mixture Example: IA=0.7092 (Sr isotope ratio of freshwater, constant today) IB=0.725 (Sr isotope ratio of freshwater, varies by location) CA=10 ppm in seawater CB=1 ppm in freshwater FA=0.6 FB=0.4 CA+B=FA\*CA+FB\*CB CA+B= (0.6\*10)+(0.4\*1)=6.4 ppm Sr Isotope ratio calculation: IA+B= FA\*CA\*IA+FB\*CB\*IB/CA+B IA+B=(0.6\*10\*0.7092)+(0.4\*1\*0.725)/6.4 IA+B=0.7102  -the measurement of 87Sr/86Sr provides a geochemical and geochronological insights about the sample. -different sources of Sr have distinct 87Sr/86Sr ratios -mantle derived materials like basalts and peridotites have low 87Sr/86Sr -crustal materials like granites and sediments have high 87Sr/86Sr -seawater's value today is 0.7092, but it has varied over geological time -by comparing the measured 87Sr/86Sr to known values, we can infer the material's origin: \--is it mantle derived (oceanic crust)? \--crust derived (continental sediments)? \--a mix of both (subduction related melts)? -if the samples 87Sr/86Sr matches the seawater ratio it suggests interaction with seawater or marine fluids. -this is used for studying hydrothermal systems, marine sediments, and carbonate rocks. Evidence of subducting or recycling -high 87Sr/86Sr in mantle derived samples may indicate recycled crustal material (subducted slabs) contributing to magma -it helps trace subduction related processes, like the contribution of sedimentary materials to arc lavas. Age dating -the isotope 87Sr is produced by the radioactive decay of 87Rb, with half llife of 48.8 billion years. -the 87Sr/86Sr ratio can be used to determine the age of rocks and minerals if the Rb content is known. \--higher 87Sr/86Sr indicates older rocks, as more 87Rb has decayed Tectonic and geological processes:\ -track the interaction of continental and oceanic materials in subduction zones -reveals the history of crust mantle differentiation and recycling Key questions it can answer: -where did this sample originate? Mantle, crust or seawater?\ -what processes affected it? Subduction, recycling or fluid interaction? -how old is it? If paired with 87Rb. It helps determine rock ages -what environmental conditions were present? Ancient seawater composition or tectonic activity? A useful trick for identifying 2 component mixing -when studying systems like the mixing of seawater and freshwater, a plot of 87Sr/86Sr versus the inverse of the concertation (1/Sr) is a powerful tool to test if the system follows 2 component mixing. Linear trend= two component mixing -in a two component system, the relationship between 87Sr/86Sr and 1/Sr is linear because of the way mixing proportions affect both the isotope ratio and concentration -the slope and intercept of the line provide information about the isotopic and concertation characteristics of the two components. -if the system involves more than two components or other complex processes, the data points will scatter instead of forming a straight line. To calculate the 143Nd/144Nd ratio of a 50:50 mixture of seawater and freshwater CA=0.001 ppm CB=0.01 ppm FA=0.5 FB=0.5 IRA=0.5125 IRB=0.5115 IRA+B=(0.5\*0.001\*0.5125)+(0.5\*0.01\*0.5115)/(0.5\*0.001)+(0.5\*0.01) IRA+B=0.51159 This calculation shows how the isotopic composition of a mixture reflects the relative contribution of each component, weighted by their concentrations and isotopic ratios. Here, freshwater dominate due to its higher Nd concertation, pulling the mixtures isotope ratio closer to the IRB=0.5115. A diagram of a graph Description automatically generated  A diagram of a sea water mixing Description automatically generated with medium confidence 87Sr/86Sr vs 143Nd/144Nd  Seawater: -has a high Sr isotope ratio and a low Nd isotope ratio Freshwater: -has a higher Sr isotope ratio and a lower Nd isotope ratio -when mixing, a curve trend is produced because 87Sr/86Sr and 143Nd/144Nd behave differently due to their concentrations and istopic contributions. -seawater has a higher Sr concentration compared to freshwater so 87Sr/86Sr values are heavily influenced by seawater even in minor proportions. -conversely freshwater has more Nd, so 143Nd/144Nd values are strongly influenced by freshwater in the mix -seawater Sr/Nd ration is 100 times greater than that of freshwater -this large difference means that Sr isotopes are strongly dominated by seawater contributions, while Nd isotopes are more sensitive to the freshwater component. Water at earths surface The earths surface water, comprising oceans, seas, ice caps, rivers, groundwater and atmospheric water, representing only a small fraction of the earths total water. this is strikingly depicted by comparing the volume of all surface water as a single sphere to the size of the earth. A close-up of a planet Description automatically generated -volume of all surface water is about 1,386,000,000 km3 -the mass of oceans alone is 1.35\*10\^18 metric tonnes -the percentage of earths mass that is H2O at the surface is 0.023% Water in earth's interior: -water is stored in the earth's interior(mantle and crust) is thought to vastly exceed surface water due to: -hydrated minerals: these minerals chemically bind water within their structure -subduction processes: oceanic crust and sediments carrying water into the mantle. -estimated to be at least as much as all the surface water and possibly up to 5-10 times more. -surface water is a tiny visible fraction of earths total water budget. -interior water plays a critical role in mantle dynamics, volcanic activity, and the earths overall water cycle, even though its less accessible and largely hidden.  Key properties of water: High heat capacity: -water can absorb and store large amounts of heat without significant change in temperature -climate impact: coastal areas have milder climates compared to inland regions because water moderates temperature by absorbing heat in summer and releasing it in winter. High latent heat of fusion(melting): -a significant amount of energy is required to melt ice without raising its temperature. -environmental impact: melting ice absorbs heat, slowing temperature increases in polar regions. High latent heat of vaporization (evaporation): -it takes a lot of energy to convert water into vapor -climate impact: evaporation cools surfaces and powers the water cycle by transporting heat into the atmosphere. Excellent solvent: -water dissolves a wide range of compounds due to its polarity, making it essential for chemical reactions in biological and geological processes. -environmental impact: dissolved salts and nutrients support marine life and geochemical cycles Polar molecular structure: -water molecules are bent with a slight positive charge on the hydrogen side and slight negative charge on the oxygen side -this polarity leads to : \--hydrogen bonding: water molecules stick together, resulting in high cohesion and surface tension \--solvent properties: polarity allows water to dissolve ionic and polar substances effectively. Consequence of waters unique structure:\ -cohesion: explains why water forms droplets and has a high surface tension -adhesion: water sticks to other surfaces, important for processes like capillary action in plants -ice density: hydrogen bonds arrange water molecules in ice into a lattice that is less dense than liquid water, causing ice to float -global heat transport: waters heat storage and release drive ocean currents and aspheric weather patterns. A diagram of water molecule Description automatically generated  A chart with different types of names Description automatically generated with medium confidence Concentration of dissolved salts: -seawater contains abut 35 grams of dissolved salts per liter, equivalent to a Salinity of 35% -this means that seawater is about 3.5% salt by weight Input and residence times: -the major ions like sodium (Na) and chloride (Cl) enter seawater in large amounts from various sources like rivers, hydrothermal vents. And volcanic activity. -these ions are not very reactive, leading to long residence times in the ocean, meaning they stay in the seawater for extended periods before being removed or transformed Conservative elements: -the major ions are described as conservative because their concentrations in seawater remain relatively stable and do not vary significantly with changing environmental conditions. -this also means that the oceans are not stratified with respect to these elements, meaning their distribution is fairly uniform throughout the water column. Taste of saltwater: -the salty taste of seawater is primarily due to the presence of major cations and anions. -it is estimated that there are approximately 5\*10\^16 tons of salt dissolved in the worlds ocean.  Major anions include: Cl, S, C, Br, B, F Major cations include: Na, Mg, Ca, K, Sr Total salinity: approximately 35.169 h/kg or 35%, meaning 35 grams of salt per kilogram of seawater, which is roughly 3.5% salinity. A chart with different colored squares Description automatically generated Conservative trace elements Conservative trace elements in seawater exhibit profiles similar to major elements like sodium and chloride, meaning their concentrations remain relatively stable and are less affected by biological or environmental processes. However they are present in much lower abundances compared to major elements. Rb: present in low concentrations, reflecting its conservative behavior in seawater V(H2VO4): also found in low concentrations, consistent with its classification as a conservative trace element. Mo(MoO4): similar to vanadate, molybdate is present in trace amounts in seawater. Re(ReO4): rhenate has even lower concentrations than the previous examples, indicating its trace nature U(UO2\[CO3\]3): this complex is also classified as a conservative trace element due to its stable concentration in seawater -unlike major elements, which are present in grams/L, these conservative trace elements are measured in micromoles, nanomoles, or even picomoles per kg of seawater, indicating their much lower abundance. A chart with different colored squares Description automatically generated Particle reactive elements -particle reactive elements are those that tend to quickly absorb onto particulate matter like phytoplankton, minerals, and organic debris in the ocean. This process causes them to sink out of the surface ocean, which can significantly affect their concentrations in the water column and their distribution in the marine environment. Examples: Al: -aluminum is often associated with particulate matter in the ocean. It is primarily derived from continental weathering, industrial activities and atmospheric deposition. -it quickly absorbs to particles, leading to its removal from the water column as particles sink -it can serve as a trace for terrigenous inputs to the ocean and is used to study sedimentation processes. Th: -thorium is a naturally occurring radioactive element that is highly particle reactive. It tends to adhere to particles, especially those composed of organic matter and minerals. -Th is removed from the water column by sinking particles. Its concertation in surface waters is significantly lower due to this rapid absorption. -Th isotopes are often used as tracers in oceanography and sedimentology to study ocean circulation, particle transport and sedimentation rates.  Major nutrient elements A diagram of different types of nutrients Description automatically generated -major nutrient elements are essential for biological processes in the ocean and are typically found in relatively high concentrations. Examples: C: Dissolved organic carbon serves as a food source for microbial communities in the ocean (mmol) N(NO3):key nitrogen source for phytoplankton growth. (umol) Si(SiO2):important for the growth of diatoms and other siliceous organisms(umol) P(PO4):essential for DNA, RNA, and ATP, critical for cellular function and energy transfer. (umol) Trace nutrient elements -trace nutrient elements are required in much smaller quantities but are still essential for biological functions Examples: Fe: crucial for photosynthesis and cellular respiration in phytoplankton (nmol) Zn: essential for many enzymatic reactions and cellular processes (nmol) Cd: involved in photosynthesis and Co2 processing (nmol) Residence time The residence time **(τ)** of an element in sweater is a measure of how long, on average, an atom of that element remains dissolved in the ocean before being removed. It's a key concept in understanding the cycling of elements in marine systems. **(τ)**= total amount of the element in sweater (mass or moles)/ rate of input or removal of the element (mass or moles/yr.) Long residence time: -elements with long residence times (Na, Cl) are considered conservative -these elements are not easily removed and maintain uniform concentrations throughout the ocean. -they mix well globally and their residence times are often longer than the ocean mixing time of about 1,000 years. Short residence time: -elements with short residence times like Fe, Al, Ob are often non conservative or particle reactive -they are removed quickly from sweater, usually by absorption onto particles or through biological processes. -these elements may show large spatial variability in concertation Inputs and outputs: -Inputs include rivers, atmospheric deposition, hydrothermal vents, and submarine groundwater discharge. -outputs include processes like sedimentation, incorporation into biogenic material, or reaction with ocean crust. -residence time is like the time it would take to fill the ocean with a given element if the current input rate continued.  A blue screen with black text Description automatically generated Residence time of UCSB students Τ=total number of undergrads/ numbers graduating each year Τ=16,000/3,500=4.57 yrs.  Residence time and ocean mixing: Residence time (τ) describes the average time an atom of an element remains in seawater. -elements with τ greater than 2-3 Kyr tend to exhibit conservative behavior. \--their concentrations remain relatively uniform across the ocean due to their long residence times compared to the oceans mixing time (1-2 Kyr) -elements with shorter residence time (less than 2 Kyr) tend to be non-conservative, as they are more influenced by biological, chemical or physical removal processes. Concentrations in seawater and crust: -high concentrations in seawater and low concentrations in the curst: these elements tend to be conservative because they persist in seawater for long periods. Examples include Na, Cl -low concentrations in seawater and high concentrations in the crust: these elements are typically non conservative due to rapid removal from seawater. Examples include Al, Th. Sr vs Nd isotopes and behavior -Sr isotopes are typically conservative in seawater, reflecting long residence times and consistent mixing. -Nd isotopes are often non conservative due to: \--shorter residence tiems (500-1000 yrs. For Nd) \--more localized variability, influenced by continental inputs, particle interactions and water masses. A diagram of different types of sea creatures Description automatically generated with medium confidence Age and pathway of seawater How we determine seawater age: Radioactive tracers: use isotopes with known decay rates: -carbon 14 (14C): formed in the atmosphere and incorporated into surface waters. As water sinks, the 14C decays, providing an estimate of the time since the water was last in contact with the atmosphere (typically tens of thousands of years for deep water) -helium 3 (3He): produced by radioactive decay of Tritium (3H). tritium is introduced to surface waters through atmospheric interactions and nuclear testing. The 3He/3H ratio can indicate water age over decades. Chlorofluorocarbons (CFCs): synthetic compounds released since the mid 20^th^ century. -they're detectable in seawater in trace amounts and provide information on circulation pathways and timescales over decades to a century. Mapping ocean circulation pathways: Analyze tracer distributions: -radioactive tracers like 14C and stable tracers like CFCs can reveal how water masses mix and move through the ocean basins. -example: the Atlantic meridional overturning circulation (AMOC) pathway, where surface water cools and sinks near the poles, flows into deep basins, and resurfaces elsewhere. Measure dissolved oxygen (O2): -deep water formed in the poles is oxygen rich. Over time, oxygen is consumed by biological activity in the deep ocean. -low O2 levels indicate older water masses. Use salinity and temperature (thermohaline properties): -different water masses have unique salinity and temperature signatures -these properties help trace where water comes from and how it mixes. Nitrogen isotopes (15N/14N): -reflect biological activity and nutrient cycling, providing indirect information about water mass history. The Suess effect and change in 14C in oceans Natural ratio of 14C/13C in earths atmophsere Production of 14C -cosmic rays collide with nitrogen in the upper atmosphere, creating radiocarbon (14C) -14C integrates into CO2 and cycles through the atmosphere, oceans and biosphere. Baseline ratio: -the natural atmospheric ratio of 14C/13C is stable under preindustrial conditions, reflecting equilibrium between production and decay. Effects of fossil fuels on 14C (the Suess effect) -Fossil fuels are ancient organic matter, depleted in 14C due to its radioactive decay over millions of years -burning fossil fuels releases large amounts of 12C and 13C, but no 14C -this increases total CO2 levels while diluting the atmospheric concentration of 14C -the observed effect is a measurable decline in change of 14C -oceans also absorb atmospheric CO2, leading to reduced 14C in surface and subsequently deeper waters as mixing occurs. Bomb effect: -mid 20^th^ century nuclear testing injected significant 14C into the atmosphere, temporarily increasing atmospheric 14C concentrations. -the atmospheric 14C levels sharply rose, with a peak in the 1960s. Impact on oceans: -this bomb radiocarbon entered the ocean via air sea exchange -higher 14C in surface waters, with a gradual decline as the excess 14C mixed into the deep ocean over decades. -ocean circulation studies use this 14C spike as a tracer for water mass movements.  Seuss effect: refers to the observed decrease in the atmospheric concentration of the radiocarbon isotope 14C due to the addition of fossil fuel derived CO2 into the atmosphere. -the absence of 14C in fossil fuels is due to its relatively short half life of 5,730 years compare to the geological timescales over which fossil fuels are formed. A blue background with black text Description automatically generated For Na and Cl, their residence times are millions of years-far longer than the mixing time of the oceans (1-2 Kyr). This allows them to be evenly distributed throughout the global oceans. -their concentrations remain relatively constant across different parts of the ocean. -their consistency is because the inputs) rivers and hydrothermal vents) and outputs (removal into sediments and evaporation process) are small compared to the standing reservoir of Na and Cl in the oceans. -the ocean contains an enormous amount of Na and Cl, forming the majority of dissolved salts in seawater. -chloride makes up 55% of the dissolve ions and sodium contributes around 30% forming the characteristic salinity of seawater of 35%. -Na and Cl are not heavily involved in biological or geochemical cycling compared to elements like N or C. -their lack of reactivity ensures that they remain in solution without significant fluctuation.  -the residence time of iron (Fe) in seawater is relatively short, often on the order of days to months, depending on environmental conditions. This short residence time indicates that iron does not stay in the ocean for long periods before being removed. -iron is considered a non conservative element because its concentration varies significantly from place to place in the ocean. -unlike conservative elements such as Na, Cl which maintain consistent concentrations, iron levels can be influenced by a variety of factors, including biological uptake, sedimentation and hydrothermal unput. -iron is a critical nutrient for phytoplankton and plays a vital role in photosynthesis and various biochemical process in the ocean. Asa. Result, its concertation can be significantly reduced in surface waters due to biological uptake. -the inputs of iron into seawater are substantial coming from source like river runoff, dust deposition form the atmosphere and hydrothermal vents. -conversely, outputs include removal through biological uptake by marine organisms and settling of particulate iron into the seafloor, making the balance between inputs and outputs significant relative to the standing reservoir of iron in the ocean. -iron concentrations can change dramatically over short distance due to varying local conditions, such as proximity to continental shelves, upwelling zones, and dust deposition areas. -the variability can lead to distinct biogeochemical zones in the ocean, with implications for marine ecosystems and nutrient cycling. Residence time Sr-1,000,000 years Ocean mixing timescale: 1,000-2,000 years Nd:500-1,000 years Pb:100 years How should Sr vs Nd isotopes vary? -Sr isotopes should show less variability and be more representative of long term integrated geological processes. -Nd isotopes should exhibit greater variability and reflect more local and recent inputs, influenced by biological activity and sediment dynamics. A map of the ocean Description automatically generated  A diagram of continental and continental Description automatically generated Old continental input: Atlantic ocean -the Atlantic ocean receives inputs from old continental crust. This crust has been subjected to extensive weathering and alteration over geological time. -the isotopic compositions like Nd and Sr of the input materials are likely to be more enriched in certain elements and isotopes like Sr and Nd that have accumulated over time. -their enriched isotopic signature is indicative of older continental sources, which have been involved in process such as differentiation, recycling and long-term weathering. -the presence of these old continental materials in the Atlantic can lead to relatively stable and well define isotopic signatures, reflecting a long history of continental input and interaction with seawater. Young arc input: pacific ocean -the pacific ocean particularly around subduction zones and volcanic arc, receives input from younger volcanic materials and newly formed continental crust. These arcs are often composed of andesitic to rhyolitic compositions, which are characteristics of young crust. -since these arc inputs are relatively young, they have not undergone the extensive geological process that old continental crust has experience. Therefore, the isotopic compositions are typically less enriched compared to those of older continental crust. -the isotopic ratios, especially for elements like Nd and Sr, may reflect a more juvenile character, indicative of recent mantle derived materials mixed with contributions from subducted oceanic crust. -the younger isotopic signatures in the pacific can show greater variability due to the dynamic processes at subductions ones and active volcanic arcs. This can lead to more rapid changes in the isotopic composition of seawater and sediments in this region. In summary, the Atlantic oceans old continental unput leads to enriched isotopic signatures, while the pacific oceans young arc input results in juvenile isotopic compositions. Estimating inputs into the oceans (2 major inputs) Input from river (continents) -rivers transport a variety of materials from the land to the oceans, including sediments, nutrients, dissolve minerals and organic matter. This input is crucial for maintaining the nutrient dynamics in coastal and open ocean regions. Sources or river input: -Weathering: the chemical and physical weathering of rocks releases ions and minerals that are carried by rivers. -soil erosion: erosion of soils in agricultural and natural landscapes contributes sediment and nutrients. -land use practices: human activities such as agriculture and urbanization, can enhance runoff and nutrient loading to rivers. Significance: -rivers are vital for delivering essential nutrients like N, P and S that support primary production in coastal and marine ecosystems. -estimating river inputs to the ocean involves measuring the concentration of various elements in river water and multiplying by river discharge. -globally, rivers contribute significant amounts of dissolved solids and nutrients, with estimates suggesting that major rivers can deliver millions of metric tons of materials to the oceans each year. Input from hydrothermal systems on ocean floor -hydrothermal system, located along mid ocean ridges and volcanic arcs, release mineral rich fluid heated by volcanic activity. These systems are significant sources of various elements and compounds to the ocean. Sources of hydrothermal input: -vent activity: hydrothermal vents emit heated, mineral laden water that contains metals like Fe, Co, Z, Pb, nutrient's and dissolved gasses. -seafloor alteration: the interaction of seawater with hot tocks alters the chemical composition of the fluids, enriching them in certain elements before they are released into the ocean. Significance: -hydrothermal inputs are critical for supplying trace metals and nutrients to the ocean, which can influence primary productivity and microbial communities in deep sea ecosystems. -they also play a role in global biogeochemical cycles, particularly for elements like carbon and sulfur. -measuring hydrothermal inputs involves direct sampling of vent fluids and analysis of their chemical composition -estimates vary widely, some studies suggest hydrothermal vents contribute significant amounts of specific elements like iron and manganese that can have important ecological roles.  More MORB input decreases seawater 87Sr/86Sr -MORBs are formed at spreading centers where tectonic plates diverge, allowing magma from the mantle to rise and solidify. -MORB has relatively low 87Sr/86Sr ratios due to its primary source in the mantle, which is less radiogenic than continental crust. -as more MORB is introduced into the oceans, either through increased volcanic activity at spreading ridges or changes in tectonic processes, it contributes less radiogenic 87Sr to the seawater. -this influx can lower the overall 87Sr/86Sr ratio in seawater, as the ocean mixes with the less radiogenic strontium form the MORB. UUC (upper continental crust) 87Sr/86Sr increases seawater 87Sr/86Sr -the upper continental crust generally has higher 87Sr/86Sr ratios compared to the mantle and MORB. This is primarily due to the weathering of rocks that are rich in RB which decays to radiogenic Sr (87Sr) -this weathering process releases more 87Sr into rivers, which eventually flow into the oceans. -when weather continental materials enter the ocean, they contribute radiogenic 87Sr to seawater, thus increasing it 87Sr/86Sr ratio. -the long term balance between the inputs from continental weathering and the inputs from MORB will determine the overall isotopic composition of seawater. Long term stability vs variability -todays seawater 87Sr/86Sr ratios remain relatively constant due to a dynamic balance between these inputs and the residence times of Sr in the ocean. -over geologic timescales, the ratios can vary significantly based on tectonic activity, continental weathering rates and climatic conditions that affect t erosion and sediment transport. -major geological events such as changes in plate tectonics, large scale weathering events, or shift in ocean circulation can lead to changes in the balance of these inputs, thus altering the 87Sr/86Sr ratio in seawater over long periods. Inputs into oceans from hydrothermal vents Hydrothermal vents, first discovered in 1977, have significantly expanded our understanding of marine ecosystem and geochemical processes in the ocean. -hydrothermal vents release a variety of dissolved minerals and nutrients into the surrounding seawater -iron (Fe) : critical for the growth of many microorganisms, including those that participate in chemosynthesis. -sulfur (S): released as hydrogen sulfide (H2S) which is utilized by chemosynthetic bacteria. -Mn, Cu, Zn and other trace elements -the chemical reactions occurring at hydrothermal vents provide energy for life forms that do not rely on sunlight through: \--chemosynthesis: organisms convert organic compound into organic matter \--chemosynthetic bacteria can produce biomass using the energy derived from these chemical reactions, supporting various life forms. Hydrothermal vents emit gases including: -carbon dioxide, contributing to oceanic carbon cycling -methane, that can be a byproduct of microbial activity and serve as an energy source for some chemosynthetic organisms. Chemosynthesis: use inorganic compounds as an energy source to convert carbon dioxide and water into glucose and other organic compounds How do we know the output of elements from oceans? -the concept of steady state implies that the inputs of elements to the ocean are balanced by the outputs. In other words, the amount of a particular element entering the ocean equals the amount leaving. Input estimates:\ inputs can be more easily measured or estimated -riverine inputs: scientists can quantify the concentrations of various elements in river waters and multiply them by the river flow rates to estimate total inputs from rivers. -atmospheric deposition: inputs from atmospheric sources like dust or precipitation can be estimated through sampling and analysis. -hydrothermal vent inputs: the output of elements from hydrothermal vents can be measured directly by studying the vent fluids. Output estimates: -estimating outputs is more challenging due to the complexity of processes involved in the removal or recycling of elements from the ocean. Here are some approaches used. -sedimentation: the amount of an element removed from the ocean can be estimated by studying the sedimentation rates and concentrations of elements in marine sediments. For example, the rate at which elements like calcium and phosphorus are buried in sediments provides an estimate of output. -biological uptake: understanding biological processes is crucial. The uptake of nutrients by marine organism can be estimated through studies of primary productivity and biomass turnoever. This provides insights into how much of certain elements are being cycled through the food web and ultimately exported to the seafloor as organic matter. -chemical fluxes: chemical models and tracer studies can help estimate how different elements are cycled within the ocean. This includes looking at fluxes between different reservoirs to estimate outputs. Given that input must equal output the general formula is : Input=output+ change in storage If the change in storage is assumed to be negligible over long time scales (as it often is for conservative elements) then: Output= input A map of the world Description automatically generated Ore deposits Volcanogenic massive sulfide (VMS) deposits:\ -VMS deposits are one of the most important types of ore deposits for the mining of base and precious metals, particularly sulfide minerals. -black smoker chimneys form at mid ocean ridges and other tectonically active regions where seawater interacts with hot magma -cold seawater penetrates fractures in the earths crust, heats up due to geothermal energy, and becomes chemically enriched by leaching metal like Fe, Cu, Zn, Pb and S from the surrounding rocks. -as the hot metal rich hydrothermal fluids are expelled into the colder ocean water, the sudden temperature drop causes the metals and sulfur to precipitate as sulfide minerals. -this precipitation creates chimneys or mounds of minerals such as pyrite (FeS2), chalcopyrite (CuFeS2), sphalerite (ZnS) and galena (PbS). -over time, these sulfide accumulations grow and can form large ore deposits on or just below the seafloor. These deposits are buried by sediments and preserved as VMS deposits in the geological record. **Key Metals Found in VMS Deposits:** - **Base Metals:** - Copper (Cu) - Zinc (Zn) - Lead (Pb) - **Precious Metals:** - Gold (Au) - Silver (Ag) - **Other Chalcophile Elements:** - Sulfur (S) - Selenium (Se)  A diagram of a solar energy Description automatically generated How much do hydrothermal vents drive seawater chemistry? -seawater circulation rate through hydrothermal vents:\ 3.2\*10\^13 kg/yr. -total global river flux: 3 to 5\*10\^16 kg/yr. -comparison of fluxes: Hydrothermal vent flux is 0.1% of the river flux. For an elements hydrothermal flux to match its riverine flux, the concentration of the element in hydrothermal fluids must be 1,000 times higher than its concertation in rivers. This factor compensates for the much smaller volume of water passing though hydrothermal systems. Why is this important: -hydrothermal systems disproportionately influence ocean chemistry for certain elements due to their high concentrations in vent fluids -this dynamic is crucial for understanding their global biogeochemical cycles of metals and nutrients, ocean crust alteration and geochemical evolution over geological timescales, the formation of ore deposits near mid ocean ridges.  -Seawater Mg reacts with feldspars in oceanic crust( albite and anorthite) and sediments to form chlorite. -this process is a major sink from Mg, removing it from seawater over geological timescales. -the reaction consumes large amounts of Mg, which reduced its concertation in seawater -this sink is important for maintaining the balance of Mg in the oceans -the reaction releases H ions, which can contribute to local acidity in alteration zones -Sodium ions are released into seawater, maintaining sodium's conservative nature in ocean chemistry -this reaction occurs in setting like hydrothermal alteration of oceanic crust at mid ocean ridges and weathering of feldspar rich rocks in marine sediments. -over time these processes contribute to the regulation of ocean chemistry, particularly the Mg/Na ratio. A diagram of a graph Description automatically generated with medium confidence Cation contributions: hydrothermal systems contribute various cations to the ocean, albeit in smaller amounts compare to riverine inputs. -alkali metals like Li, K, Rb, Cs can be enriched in hydrothermal fluids and thus contribute to seawater chemistry. -Manganese (Mn) and Iron (Fe) can also be released in significant amounts during hydrothermal processes, influencing their concentrations in the ocean. -hydrothermal vents are rich in sulfur, primarily in the form of sulfate. The hydrothermal processes can reduce sulfate to sulfide under anoxic conditions affecting the sulfur cycle in oceanic environments. Mg chemistry -hydrothermal systems serve as a sink for Mg by facilitating the uptake of Mg ions from seawater into the oceanic crust -the chemical reactions occurring at these systems can lead to the precipitation of Mg bearing minerals, which removes Mg from seawater and helps regulate its concentration in the ocean over geological timescales. Overall impact of hydrothermal systems: -small contribution but high local impact: \--while hydrothermal systems contribute a smaller total mass of elements compared to rivers, their localized influence can be significant in altering the chemical composition in their vicinity. \--hydrothermal systems are integral to the cycling of several elements, including cations and sulfur species, connecting geological processes with oceanographic and biogeochemical cycles. Hydrothermal vent chemistry: -the unique chemistry of hydrothermal fluids can support diverse biological communities that thrive on chemosynthesis, fundamentally linking geology and biology in the deep ocean. -the interaction of seawater with hot, mineral rich fluids at hydrothermal vents leads to the alteration of both the fluids and the surrounding rock, creating new mineral deposits and changing the oceans chemical landscape.  The interactions between hydrothermal fluids and seawater lead to significant changes in pH, oxidation state, and temperature, which in turn affect the solubility and precipitation of various minerals, including sulfides. pH changes: -hydrothermal fluids that emerge from seafloor are typically at elevated temperatures and may have a lower pH (more acidic) compared to seawater. -when these fluids mix with seawater, the pH tends to increase due to buffering capacity of seawater -the mixing of acidic hydrothermal fluids with basic seawater can lead to significant changes in the chemical composition of the resulting fluid. Oxidation state: -hydrothermal fluids often contain reduced species such as hydrogen sulfide (H2S) and ferrous iron (Fe2+). -upon mixing with oxygen rich seawater, these reduced compounds can oxidize, leading to the formation of oxidized species. -the oxidation of sulfide and other reduced species contributes to the overall chemistry of the vent fluids and affects biological activity in the vicinity. Temperature increase: -hydrothermal fluids are typically much hotter than the surrounding seawater (often exceeding 300 C or higher). upon venting, these hot fluids can cause localized heating of seawater. -the high temperatures can drive chemical reactions that would not occur at lower temperatures, influencing the solubility of minerals. Solubility and precipitation: -as temperatures decrease and pH increases upon mixing seawater, sulfide like iron and copper, that were previously soluble in the hot hydrothermal fluids become less soluble. -the decrease in solubility leads to the precipitation of these sulfide, often forming black smoke due to the fine particulate nature of the precipitates. Black smokers: \- the black smoke observed at hydrothermal vents is primarily composed of tiny particles of iron sulfide and other metal sulfides that precipitate out of the hydrothermal fluids when they come into contact with cold seawater. -this creates visible plumes that rise form the seafloor and can significantly impact local marine ecosystems. -the precipitates from hydrothermal vents provide habitats and energy sources for unique biological communities, primarily relying on chemosynthesis rather than photosynthesis. -the metals and minerals released during this process can also contribute to the formation of mineral deposits, such as volcanogenic massive sulfide (VMS) deposits. A close-up of a smoke cloud Description automatically generated the smoke emitted form hydrothermal vents is not smoke in the traditional sense, but rather clouds of precipitating metal sulfides. -the clouds consist primarily of fine particles of metal sulfide, such as iron sulfide (FeS), copper sulfide (CuS) and zinc sulfide (ZnS). These metals are often present in the hydrothermal fluids in dissolved forms. -the precipitates are typically very small, which allows them to remain suspended in the fluid and create the visual appearance of a smoky plume. -the black appearance of the smoke is primarily due to the presence of iron sulfide and other metal sulfide, which can absorb light. The concentration of these particles can create a dramatic visual effect, with plumes often appearing as dark clouds rising from the ocean floor.  Black smokers: focused discharge -typically found along mid ocean ridges and other tectonic plate boundaries where seawater interacts with hot magma and hydrothermal systems. -the fluids emitted from black smokers are very hot, often exceeding 350 C -as the hot, mineral rich hydrothermal fluids mix with the much cooler seawater, the sudden drop in temperature leads to the precipitation of metal sulfide. This is why black smokers emit a dark, smoky plume. -the clouds of black smoke are due to the formation of tiny particles of metal sulfide, which create the characteristic of a black color. -the precipitation of sulfide occurs rapidly at the interface where the hot fluids meet the cold seawater, resulting in the formation of these striking back plumes. Clear fluid vents or white smokers: diffuse discharge -clear fluid vents may be found at slightly lower temperatures than black smokers and can occur at various ocean depths. -the fluids from these vents are generally cooler than those of black smokers, often ranging from 30 C to 350 C -in this case, sulfide may precipitate at greater depths, or the concentrations of sulfide minerals may be lower, resulting in clearer fluid emissions. The fluid may still contain dissolved minerals and nutrient but in lower concentrations than those found in lack smokers. -the emissions are less visually dramatic than those of black smokers and may appear clearer or lighter in color due to lower concentrations of suspended particles. Two types of up flow zones: -hydrothermal systems can have various up flow zones where hydrothermal fluids rise from the ocean floor. The different temperatures and chemical compositions lead to the formation of black smokers or clear fluid vents. -the precipitation of sulfide at different depths and temperatures influences the characteristics of the emitted fluids, affecting both their appearance and their ecological implications. ------------- ----------------------- ----------------------- **Feature** **Focused Discharge** **Diffuse Discharge** ------------- ----------------------- ----------------------- --------------- ------ ----- **Flow Rate** High Low --------------- ------ ----- ----------------- ---------------------- --------------------------- **Temperature** High (often \>350°C) Lower (typically \ Ca+2HCO3+H4SiO4 -carbonate precipitation in oceans Ca+2HCO3-\>CaCo3+H2O+CO2 In the absence of human influence, volcanic CO2 emissions were balanced by the rate of CO2 drawdown via silicate weathering and carbonate burial. This balance stabilized earth's climate over geological timescales, acting as a natural thermostat. A diagram of a carbon cycle Description automatically generated Human activity, such as fossil fuel burning and deforestation, now release 40 Gt of Co2 annually, overwhelming natural processes and leading to rapid atmospheric CO2 increases and global warming -humans are outpacing nature by 100 times  Climate change observed in the past 150 years, marks the shift from natural climatic variations to human induced changes in the earths carbon cycle. -fossil fuel combustion release significant amounts of CO2 and other greenhouse gases into the atmosphere -deforestation reduce the number of trees that can absorb CO2 though photosynthesis -atmospheric concertation's have risen from 280 ppm to 400 ppm -methane and nitrous oxide have also increased Disruption of natural carbon cycle -the balance between volcanic CO2 emissions and Co2 drawdown via silicate weathering maintained a stable climate -the rapid increase in CO2 has overwhelmed this natural cycle, leading to a net increase in CO2 and contributing to climate warming -higher CO2 levels enhance the greenhouse effect, trapping more heat and leading to global warming -as temperatures rise, this may lead to changes in weather patterns, ice melt, and changes in ocean chemistry A person standing in front of a graph Description automatically generated The keeling curve is a graph that illustrates the ongoing increase in atmospheric carbon dioxide concentrations since the late 1950s. -the curve displays the concentration of CO2 in ppm vs time -it shows the upward trend in CO2 levels, particularly accelerating since the mid 20^th^ century -the curve exhibits seasonal fluctuations with CO2 levels rising during the winter months , where plants are dormant and CO2 is not absorbed as much, and falling during the summer months, where photosynthesis is more active. -this seasonal cycle is superimposed on the overall increasing trend, reflecting the natural processes of carbon cycling in terrestrial ecosystems.  A graph of temperature and temperature Description automatically generated -pre industrial levels averaged around 280 ppm -over the last 200 years, there has been increase in co2 levels due to humans, 400 ppm -historical co2 levels exhibited small oscillation, generally staying within a range of \