Earth Systems Flashcards

Question

Re: stable isotopes and space List samples A, B and C in order of increasing sample processing. Explain your reasoning.

Answer 1

1. Sample B: Interstellar material 2. Sample C: Meteorite macromolecule 3. Sample A: Earth organic matter Reflecting degree of chemical and physical processing.

Answer 2

A system comprises interrelated components functioning as a complex whole

Answer 3

Individual part of a system or sub-system

Answer 4

Nature of a system at any point in time | (set of attributes - e.g. room t, noise level, etc)

Answer 5

* Link between system components * Change in one component results in a change in the same direction for another

Answer 6

Change in one component results in a change in the same direction for another

Answer 7

Change in one component results in a change in the opposite direction in another

Answer 8

* Self-perpetuating mechanism of change and response. * Negative feedback loops diminish effects of disturbance. * Positive feedback loops amplify effects of disturbance.

Answer 9

* Negative feedback * Stable * Equilibrium state * Positive feedback * Unstable * Slightest disturbance * System driven away from equilibrium * Imagine all possible states as a hilly surface where valleys represent stable states and hills, unstable states; with a ball being the current state.

Answer 10

* The ball can roll back into a stable state in the valley after a small disturbance with a nehative feedback loop diminishing effects of the disturbance (states controlled by negative feedbacks are stable). * A large disturbance can force system into new equilibrium state (over the hill, into next valley).

Answer 11

* Ball starts at the top of a hill * After small disturbance ball **accelerates** until in new position (no negative feedback to move back to previous position) * Positive feedback enhances effects of disturbance - rapid change until new state is found * States controlled by positive feedbacks are unstable

Answer 12

* Glacial deposits (**tillites**) on all continents, all latitudes. * Laterally extensive marine sediments indicating anoxia (**Banded Iron Fms** deposited in absence of oxygen). * Rapidly replaced by non-glacial, warm, shallow marine **"cap" carbonates**, indicating rapid transition from cold to warm conditions.

Answer 13

* Single snowball cycle * Ice reaches 30° * Runaway albedo * CO2 build up * Runaway greenhouse * CO2 drawdown * Silicate weathering * Photosynthesis

Answer 14

* Stable = they are not radioactive * Isotopes * Chemically identical * same number of electrons and protons * different masses * different number of neutrons * Occurence, different relative abundances * Effects * Different masses, different bond frequencies, affects **zero points** * ****Lighter isotopes, smaller energies needed = more reactive

Answer 15

* Zero point energy * lowest possible energy a system can have * non-zero ground state * vibration never zero * Isotopes have different zero-point energies * e.g. hydrogen bonds

Answer 16

* Carbon isotopes take two different forms in the Earth system, C-12 and C-13, in different relative abundances. * Carbon reservoirs are oxidised and reduced. * Photosynthesis uses C-12 preferentially; sinking and burial stores C-12. * Less C-12 for carbonates or further OM production. * C-13/C-12 ratio reflects rate of production, sinking and burial. * Ratio of sample compared to a standard: d¹³C (%_o) = **[(¹³C/¹²C_spl - ¹³C/¹²C_std) / (¹³C/¹²C_std)] x 1000**

Answer 17

* Carbon isotope records (d13C carbonates, d13C organic) reflect reservoir sizes. * ~Constant values for at least 3.5 Ga * Notable events at 2.1-1.8 and 1.0-0.7 Ga. * Causes * Rifting and orogeny * Clastic supply * Nutrient supply * Productivity and organic deposition

Answer 18

* Major biological events * Major depositional events * Volcanism * Weathering * Proterozic ice age * Drop in productivity * Decline in d13C

Answer 19

* Significant d13Ccarb variation * Major depositional events * Volcanism * Weathering * e.g. Silurian-Devonian - increased silicate weathering; marine regression; land plants * e.g. Carboniferous - evolution of biopolymers; organic deposition; increase in d13C

Answer 20

* Using a simple mixing ratio: * Plants (are a carbon reservoir and) take in C-12 preferentially, produce OM which is sometimes buried. * Some of this OM after its production during photosynthesis is used for energy, e.g. starch, carbohydrates. This energy source is is used for bio-chemical machinery of life. * T.f. OM comes from CO2 and water, passes through metabolism, and some is respired and converted back to CO2 and water - with the release of energy being the only thing that changes. * The respired CO2 (rich in light C-12) is either released into the atmosphere or into the soil. * (The C-12 released acts as a tracer of the source of the C.) * T.f. part of the C in the soil is C-12 from respiration. * Additionally, atmospheric CO2 percolates into the soil (into the pores, gaps and cracks), t.f. producing a mixture of respired CO2, rich in C-12, and atmospheric CO2, richer in C-13. * Diagnostically, the important thing is you get more CO2 from the atmosphere incorporated into the soil when atmospheric CO2 levels are high. * T.f. when measuring the **isotopic composition** (d¹³C; ratio of C-13 to C-12) of the paleosol, the values tell of the mixing ratio between respired and atmospheric CO2 - assuming that plants are producing the same amount of respired CO2 through time, and any variation is due to atmospheric CO2 input, related to the pressure of CO2 in the atmosphere.

Answer 21

* Used to determine **steroid abuse**: * Use d13C to determine what a person has admistered vs what is produced naturally in the body. * For e.g., an athlete may administer **anabolic** steroids for **performance enhancement** purposes. * World Anti-Doping Agency * Athletes no longer take **exogenous** steroids (e.g. Stanozol) bc it's not present naturally in the body and can be easily found out. * Most common anabolic steroid taken amongst athletes is t.f. **testosterone** (also **androgenic**) to _supplement_ the testosterone levels already in the body. * Bc it is produced naturally in the body (it's **endogenous**), its structure cannot be used to determine whether a person is doping, but the _source_ of the synthesised testosterone is not anthropogenic, its **botanic**, and so the d13C can be used. * **Stigmasterol** generated in plants can be transformed into testosterone pharmacutically - plants are rich in C-12, and humans are not due to their _varied diets_. * Synthetic steroids produced in this way have a similar d13C to **C3 plants**. * T.f. if, from a **blood or urine sample** the steroid compounds (e.g. testosterone) have (i) a d13C identical to/similar to C3 plants; and (ii) different/lighter d13C compared to the d13C of **indigenous reference compounds**, then GUILTY. * Indigenous reference compounds are steroids produced naturally in the body, like **cholerserol**, that don't posses any performance enhancing capabilities and would t.f. not be administered and posses the d13C produced naturally within the person's body. * I.e. if testosterone is C-12 rich, and cholesterol is more C-13 rich - GUILTY.

Answer 22

* Extraction * Supercritical fluid extraction (SFE) * Retains volatiles * Efficient/selective * Contaminant free * Pyrolysis * Hydrous pyrolysis * Thermal decomposition * \>300°C & 72 hrs * Liquid water * High yeilds

Answer 23

* Meteorites are fragments of asteroids that are _unprocessed_ and posses _4.6 Byr old matter_, from the birth of the solar system. * There will be fractions that pre-date the solar system, with d13C beyond the signatures of our solar system (interstellar signatures). * **_Carbonaceous chondrites_** are primitive meteorites, possesing **2-5% OM** (_25%_ solvent soluble, "**free**"; _75%_ insoluble, **macromolecular**) with _varied d13C_. * This meteoritic organic matter holds _record of solar system evolution_ (preceeding asteroid formation) and _several environments_ (e.g. interstellar could, solar nebula). * E.g. **Murchison** * It is important to know if the d13C's are true or are from terrestrial contamination. * Also, the presence of a **mixture of large and small**, and **stable and unstable** organic componds reflects its **_unprocessed_** nature.

Answer 24

* high d13C of **20-25** in meteorite **amino acids**; * relatively high d13C of **-10** in **organic C** compared to earth materials; * really high **CO₂** and **carbonate** d13C of **30-50**; * also **high dD** (deuterium) is a _non terrestrial signature_, **1000-2500** in meteorite **amino acids**.

Answer 25

* Aromatic hydrocarbons become enriched in C-12 down the reaction sequence as the carbon number is increased (building more complex C compounds from simpler precursors), i.e. making bonds \>12C in products (synthesis) * Also show the opposite in a "cracking reaction", where breaking bonds \>12C in products, and larger starting materials break into smaller compounds. * In either case, C-12 always becomes more enriched in the reaction product. * So have opposite reactions taking place from central point. * The same/similar trend is followed in the macromolecules, the major organic component of the meteorite. * The processes are indicated as such bc stable isotopes are good for indicating whether similar processes take place in different compounds, bc the sources are the same - they are genetically linked. * However, free compounds always slightly more C-12 enriched (determined by comparison vs pyrolysis fragments of macromolecular material).

Answer 26

* Free aromatics, from pre-terrestrial generation, have lighter d13C than pyrolysate aromatics generated at present day in the lab. * Pyrolysate aromatics t.f. have more C-13 enriched reservoir. * This demonstrates that the macromolecules present in the asteroid started to break down at some point in the pre-terrestrial past and became more enriched in C-12 during the reaction. * The same sample, in modern day, is taken to the lab and the macromolecule is broken down again, extending the degredation process. * But bc the lightest C has already gone, the second attempt is slightly more enriched in C-13.

Answer 27

* If an element has more than one rare stable isotopes (e.g. 16O, 17O, 18O) the _fractionation patterns_ of the two rare isotopes is _predictable_. * Based soley on **mass effects**, the amount of _fractionation increases as the mass increases_. * Example: If a reaction **isotopically discriminates against 18O** it will _discriminate *less* for 17O_, by roughly a **factor of 2**. * So, based soley on mass-dependent fractionation, if you know the d18O, then you also know the d17O. The _slope of a d17O vs d18O plot is 0.5_. * So what are the points that fall off the mass-dependent line...?

Answer 28

* Mass-independent fractionation refers to any _process that seperates isotopes_, that **does not _scale_ in proportion with the difference in the masses of the isotopes**. * Mass-independent fractionation processes are _uncommon_, occuring mainly in _photochemical and spin-forbidden reactions_. * Found mainly associated with _atmospheric chemistry_, **effect can be preserved** as _many geochemical reactions in water and rock are *mass-dependent*_.

Answer 29

* **Negative feedback** loops have an _odd number of negative couplings_ (- x + = -) * **Positive feedback** loops have _only positives_ or an _even number of negative couplings_ (- x - ; or, + x +, = +)

Answer 30

An atmosphere that exists immediately after the planet's formation

Answer 31

Forms after the primary atmosphere is lost

Answer 32

* Primary atmospheres form from earliest solar system, 4.56 Ga * Giant disk of dust and gas * Planets formed by positive feedback of accretion and gravitational attraction * Dust grains to larger bodies * Larger bodies had atmospheres * The origin of gas has a combination of four possible mechanisms: * **Solar nebula theory** * **Accretion theory** * **Solar wind theory** * **Comet/asteroid theory**

Answer 33

* Gravitational attraction * Gas from solar nebula * Requires planets to grow quickly, before nebula gas dissipates within 10 Myr of nebula lifetime * Earth & Venus * 60% Earth's mass in 10-20 Myrs * Long enough to capture substantial atmosphere * Mars * Smaller * Uncertain if massive enough

Answer 34

* Volatiles carried into the growing planets by infalling planetesimals and dust * Easily driven out with heating * Gases released from minerals as planets heated up * Contributions would be similar to those found in primitive meteorites * H₂O, CO₂, N₂, CH₄, NH₃

Answer 35

* Atmospheres caught from solar wind * Plasma (primarily protons and electrons with ionised gas of many elements) * 300 km s-1 * 1000 km s-1 during flares

Answer 36

* Volatile-rich comets and asteroids * Late veneer

Answer 37

* Outer earth reservoirs = atmosphere, hydrosphere and crust. * Earth volatiles (relative) different from Sun - **fractioned relative to Sun**; _Similar to chondrites_ * Other similarities to chondrites = atmosphere **noble gases**; Earth **D/H** * Differences from chondrites = _absolute abundances lower, xenon depleted_. * **Chondritic source**: asteroid belt, kuiper belt, giant planet regions - final stages of Earth formation

Answer 38

* Secondary atmospheres evolved from, or after, primary atmospheres. * Several mechanisms: * Atmospheric loss (**thermal** and **hydrodynamic escape** and other) * Outgassing from interior (**volcanic eruptions**, juvenile gases) * **Crustal interactions** (weathering, CO2 to carbonate, condensation of H2O into ice) * **Photochemistry** * **Photosynthesis** (LIFE a major contributor)

Answer 39

* **Higher T's, more rapid movemements** * Distribution of speeds * Exceptionally _fast_ gas molecules can **escape pletary gravity** * This is critical speed is called the **escape speed** * Earth's atmosphere * **No lid** so _molecules moving faster than escape speed are lost continually_ * *All planets are constantly losing a proportion of their atmospheres*

Answer 40

* Temp: Hotter atmospheres have greater average molecular speeds, higher chances of molecules leaving * Molecular size: molecules have different masses; average speed for one gas will be different from another * Planetary gravity: bigger planet can hold on to smaller molecules; Mars - CO2; Jupiter H2 * Implication: A planet's atmopshere can change through time bc of physical processes

Answer 41

For a planet to retain a gas over time, mean speed of molecules must be less than one sixth escape speed

Answer 42

* Intense extreme UV radiation * Hydrogen expands at supersonic speeds * Exerts forces on heavier molecules (push; pushes them out) * Lighter molecules entrained (drag; drags them out) * Notable occurances: Pluto, Triton (Neptune's largest moon)

Answer 43

* **Atmospheric cratering** (molecules reach escape speed during impact) e.g. Mars 50-90% loss; Earth in Moon forming event * **Solar wind** (ionization of heavier gases by solar UV; CO, N2; convected in the magnetosphere) e.g. Mercury's gases lost this way

Answer 44

* Terrestrial planets have "volcanic" atmospheres * Volcanic gasses are water rich * Without water they look planetary, similar to Mars and Venus * Valid comparison - most water is cycled near surface

Answer 45

* Silicate weathering * Carbonate ppt * Combination of these two reactions results in one CO2 molecule being removed from the atmosphere

Answer 46

* Hadean Earth * 4.5 - 3.8 Ga oceans formed * CO2 dissolves in water * CO2 removed from atmosphere by rain * Drop in atmospheric CO2

Answer 47

* E.g. **photolytic dissociation** * Water was a source of oxygen on prebiotic Earth * **2H₂O + UV → 2H₂ + O₂** * 10^-12 to 10^-14 present atmospheric level * Some products recombine * 2H₂ + O₂ → 2H₂O * Often **light products (e.g. H₂) are permanently lost to space** (Venus lost all its water this way; Earth lost a third of its water this way) * **Auto-oxidation** of carbon dioxide * **2CO₂ + UV → 2CO + O₂** * Mars 0.13% O₂ formed this way

Answer 48

* Photosynthetic organisms capture sunlight and transform in into organic compounds * Organic compounds fuel the biosphere (stored energy is released via respiration) * To oxygenate the atmosphere the cycle must be interrupted * Each carbon atom buried releases one O₂ molecule

Answer 49

* Nuclear fusion (4 x ¹H = ⁴He) * Long term evolution * Fusion gives volume reduction, but core does not shrink - heats up to maintain pressure * Higher core T's (increase reactions, faster rates of fusion, higher energy output) * Luminosity (hydrogen fuel depletion, luminosity (brightness) increases)

Answer 50

The Faint Young Sun paradox describes the evidence for liquid water at the surface of the Earth during the Archaean despite the Sun being about 25-30% less luminous

Answer 51

Oxygenation of the atmosphere around 2.4 Ga was immediately followed by the Huronian glaciation; this suggests that atmospheric oxygen destroyed a reducing greenhouse gas. Some greenhouse gases brought to Earth by meteorites.

Answer 52

* 3,8 Ga sedimentary rocks that require liquid water * Life at least 3.5 Ga - requires water also

Answer 53

* Suggestion that a **More massive Sun**, brighter in the early solar system, accounts for T difference, and that Sun mass lost since formation. * Solar wind caused outflow of charged particles from corona * 1% mass loss over geol time * 10,000 too small to put into models * Suggestion that mass lost in T-Tauri stage, which is known to cause rapid loss to young stars *but* only over the course of 1 Myrs! * Earth took 10 Myrs to form, t.f. T-Tauri over too early. * Earth-bound scenario needed!

Answer 54

* Planetary albedo * Current albedo = 0.3 * 70% solar luminosity requires 0.0 albedo which is impossible (e.g. clouds) * Geothermal heat sources * For radioactive decay to be a solution, 70% SL needs 70 Wm-2. * Modern is only 0.06 Wm-2, and it was 4-5 times this 4 Ga but that's still not enough. * Greenhouse effect (water vapour, but precipitates; ammonia, destroyed by UV; CO2). * Atmospheres can influence habitability * Planetary atmospheres can retain heat owing to the greenhouse effect * CO2, water, methane are all GHGs.

Answer 55

* Fewer CO2 sinks (small continents, little silicate weathering, small carbonate stores) * More CO2 sources (impact degassing, enhanced volcanism) * Amounts needed: * 70% SL needs **0.3 bar**, 1000 times present day * Carbonate reservoir = **60 bar**, t.f. _only 0.5% of that needed_ (and can assume that CO₂ wasn't all ppt at that point) * Ocean covered Earth - 10 bar pressure

Answer 56

* 10²⁰ kg surface carbonate today, assume same amount 4.5 Ga * No continents so no land storage - atmosphere, ocean and sea floor only reservoirs * More dissolved inorganic carbon, higher heat flux and conditions for forming carbonated basalts * Assume 100% efficiency for carbon removal in vents, and a seafloor lifetime of 60 Ma - ocean through vents in 10 Ma. * Carbon 6:1, seafloor : ocean * 1/7 (15%) of 10²⁰ kg carbonate present in atmosphere + ocean: * 0.15 x 10²⁰ kg = 0.85 x 10¹⁹ kg * Present day 4.076 x 10¹⁶ * **Hadean had 400 times more CO₂** in atmosphere and ocean than present day- GH effect

Answer 57

* Sun-like stars are best for habitable zones * Flux of radiant energy from Sun is related to distance and drops by inverse-square law * Effective T related to T of surface and atmosphere of planet * Earth-like planet with liquid water at the surface related to luminosity and distance from star (models say 0.95 - 1.1 au). * Would have runaway GH (& albedo) with stabalization of CO2 feedbacks (silicate weathering drops 1.5 au (near Mars)) * Star luminosity increases with time and HZ moves outwards * There's a continuously habitable zone that overlaps HZ at all times, CHZ narrower than HZ, 1.25 au

Answer 58

* Midway through star's life * Mass relative to Sun * Distance in au * Red star * closer than 1au * ca. 0.1 tidal locking * Blue star * further than 1 au * short lifetime * hottest star 10s Ma, sun 10 Ga * high T, high wavelength * peak in UV light * splits O2, super ozone layer? * Sun like stars best for HZ

Answer 59

Photochemistry Photosynthesis

Answer 60

* E.g. Photolytic dissociation (source of oxygen on prebiotic Earth) * Water, H₂O + UV → 2H₂ + O₂ * CO₂, 2CO₂ + UV → 2CO + O₂ * Very small amounts: 10^-12 to 10^-14present atmospheric level (PAL)

Answer 61

Light + nCO₂ + nH₂O → (CH₂O)n + nO₂ * Respiration, (CH₂O)n + nO₂ → nCO₂ + nH₂O + energy * Balanced equations * Interuption of cycle * Burial of OM (CH₂O)n allows O₂ to accumulate * Each C atmon buried releases one O₂ molecule to the atmosphere

Answer 62

* Iron and oxygen * Banded iron fms * Red beds * Uranium and oxygen * Detrital uraninites * Oklo natural reactor * Paleosols * Iron profiles * Soil-rock relationships * Sulfur stable isotopes * Mass independent fractionation

Answer 63

* Iron has 3 oxidation states * Least oxidized: metallic iron, Fe; rapidly oxidised at present day. * FeO (ferrous iron) forms under partly oxidising conditions * Fe₂O₃ (ferric iron, haematite; Fe₂O₃.3H₂O, limonite/rust) forms under highly oxidising conditions * Variable solubilities - Fe²⁺ soluble in water; Fe³⁺ insoluble * Only Fe³⁺ oxides persist in nature

Answer 64

* BIFs extend over thousands of square kms. * The iron must originally have been held in solution in the soluble ferrous state. * Huge quantities of iron in BIFs could only have been transported into the areas in which they were deposited if the ocean was mostly oxygen-free. * Gases readily transfer between the atmosphere and ocean. * It follows, t.f., that at the time the atmosphere cannot have been highly oxidising. * If it were, the oxygen-rich waters would simply cause the iron to be ppt nearer to its source. * But process poorly understood

Answer 65

* Lots of BIF deposits older than 2 Ga (e.g. Isua group, Greenland 3.8 Ga) * Only few BIFs younger than 2 Ga * (On five continents between 0.7 - 0.55 Ga, Snowball Earth) * Around 2 Ga the oxidation state of the ocean and, t.f., the atmosphere changed decisively. * Great Oxidation Event 2.3 Ga

Answer 66

* Ancient rocks with iron oxide staining are *prima facie* evidence of an oxidising environment. * No red beds older than 2 Ga (e.g. Huronian fms Ontario, Canada) * Prior to 2.3 Ga (GOE), the oxygen content of the atmosphere was insufficient to oxidise all the iron minerals at the surface of the Earth. * Oxygen depletion replaced by oxygen abundance.

Answer 67

* Rhythmic alternation of dark brown, iron-rich layers with lighter coloured, iron-poor layers * Iron oxides make up the iron-rich bands * Iron-poor bands consist mostly of flinty silica (SiO2), also known as chert * Layers are of centimetre scale with sub-millimetre size microbanding * Larger scale rhythmic banding is known in some deposits * Individual bands only millimetres thick can be traced for tens of kilometres

Answer 68

* Uranium shows the opposite relationship to iron: * It's reduced form (U⁴⁺) is extremely insoluble in water, and its oxidised form (U⁶⁺) is soluble in water. * Uraninite (f.k.a. pitchblende; U₃O₈) is a partially reduced oxide, and is not stable at the Earth's surface today. The ore would be oxidised to its soluble form and leached away. * **2.45 Ga** detrital uraninite deposits are found at **Blind River** and **Elliot Lake** in **Ontario, Canada**. * Before ~2 Ga similar deposits of uraninite occur elsewhere in the world. * After ~2 Ga detrital uraninite deposits dissapear from the geo. record. * Indicates a decisive change in the atmosphere, roughly coincident with that signalled by the disappearence of BIFs. * Uraninite grains could not have survived in an oxidising atmosphere. So before 2 Ga the atmosphere must have been more reducing than the present day.

Answer 69

* Oklo (Gabon, Africa) has **1.8 Ga Uranium ore** deposits that is severely depleted in the radioactive isotope ²³⁵U, indicating that the deposit had gone 'critical'. * U-235 had long ago decayed to different daughter products and so a critical mass of uranium must have accumulated. * Sufficient U-235 accumulated for chain reactions to start; neutrons from some uranium atoms caused fission of others, liberating yet more neutrons. * The reactions continued for many years, generating gentle heat

Answer 70

* In the present oxygen-rich atmosphere, eroded uranium is dissolved in water and transported. * Some oxidised uranium may encounter organic material, rotting vegetation and logs of wood. * Bacterial processes use up all the oxygen, and create locally reducing conditions. * Uranium becomes insoluble and is deposited. * Through time, large concentrations of uranium builds up in decomposing organic matter, sometimes within individual logs. * 1.8 Ga, the only organic matter was algal or bacterial mats * A concentration process was operating at Oklo, Gabon, Africa. * T.f. @ 1.8 Ga, the atmosphere must have been oxidissing to allow transport of water-soluble uranium that was then accumulated at Oklo.

Answer 71

* Look at distribution of iron in a profile through the soil. * Ferrous (Fe2+) iron is soluble in water and ferric (Fe3+) iron is insoluble in water. * Whether iron is present in its ferrous or ferric state depends on whether the local environment is reducing or oxidising. * So determining whether water has transported iron away, or left it in place, at some point in the past can tell us if conditions were oxygen-poor or oxygen-rich.

Answer 72

* Water exiting from the base will contain iron in the ferrous (Fe2+) form. * This is soluble in water and can be transported down through the soil and out through the holes. * Palaeosols that were in contact with a reducing atmosphere when they formed will themselves be reduced and the ferrous (Fe2+) form of iron will be dominant. * Ferrous iron is soluble in water and so percolating fluids will transport iron down through the soil profile. * Reduced palaeosols, t.f., will have lost much of their iron from their top layers and iron will increase in abundance downwards.

Answer 73

* Water exiting from the base of pot will not contain iron. * Iron present as ferric (Fe3+) form which is insoluble in water and cannot be moved from its sites in the soil. * Palaeosols that were in contact with an oxidising atmosphere when they formed will be oxidised and will be dominated by ferric (Fe3+) iron. * Ferric iron is insoluble in water and so percolating fluids will not be able to transport it. * Iron abundance in an oxidised soil profile should be reletively constant with depth.

Answer 74

* When fossil soils from around the world are examined, a consistent picture emerges. * All the well studied examples less than 1.9 Ga indicate highly oxidised conditions. * Those older than 2.2 Ga reveal reducing conditions. * Best explained by a sharp increase in atmospheric oxygen around 2 Ga.

Answer 75

* Four naturally occuring isotopes ³²S (94.9%), ³³S (0.76%), ³⁴S (4.29%) and ³⁶S (0.02%). * Mass dependent fractionation (MDF) controlled by mass difference and has specific rules (d³³S ~0.5 x d³⁴S ; d³⁶S ~2 x d³⁴S) and correlated relationships. * Mass independent fractionation (MIF) has different controls and lost proportionally: * Causes: volcanic eruptions, gas phase reactions, photochemical oxidation * Cannot occur if even small amounts of oxygen present * Ozone layer must be absent * No significant atmospheric component in present day sulfur cycle.

Answer 76

* Labratory studies show that: * Prior to 2.45 Ga (Stage I), the oxygen content of the atmosphere was low enough (\<10^-5 pal) to allow mass independent fractionation (MIF). * Onset of oxidation occured in a period between 2.45 and 2 Ga (Stage II); "Great Oxidation Event; oxygen levels \> 10-2 pal. * Oxidation was complete after 2 Ga (Stage III); oxygenated atmosphere - no MIF.

Answer 77

• Evidence from the rock record point to an increase in atmospheric oxygen levels between 2.5 and about 2 Ga. • A three-stage, "Three Box" summary model conveniently expresses the changes. The atmosphere, deep ocean and surface ocean form three distinct reservoirs for oxygen. • Stage I, which persisted until about 2.5 Ga, all three reservoirs were anoxic. This is indicated by the absence of red beds and the preservation of detrital uranium minerals. • Hydrothermal vents ('black smokers') delivered vast amounts of reduced ferrous iron into deep oceans. • Local 'oases' in productive regions of ocean surface waters where photosynthesizing organisms flourished. • The Earth would be steadily oxidized as atmospheric CH4 from methanogenic bacteria was photolytically decomposed and H is lost to space. • Initially, all the oxygen produced was mopped up immediately in oxidizing reduced gases exhaled by volcanoes. • Stage II, between about 2.1 and 1.85 Ga, the atmosphere was oxidizing, but the oceans may have been stratified, with anoxic deep waters overlain by oxygenated surface waters. • Both red beds and BIFS were widely deposited, indicating that the deep oceans were anoxic then, while the land surface was oxidising. • Stage III, all three reservoirs were fully oxidizing, as in the modern Earth.

Answer 78

* More dissolved oxygen in water * Bigger marine organisms * Corals, foramifera, brachiopods * E.g. Carboniferous producids * Gigantoproductus 30 cm across * Greater atmospheric density * Flapping is more efficient * Bigger flying insects e.g. Meganeura Monyi \> 75 cm wing span * Metabolism - bigger worms and insects respire by passive dissusion; spiracles and trachea; surface area limited: carboniferous cockroach 30 cm long * Increased oxygen resulted in amphibian-reptile transition; the animal colonization of land. * Breathing loses water, more oxygen less water loss. * Amphibian eggs have thin, permeable membrane while reptiles reproduce by amniotic egg. Amniotic egg has porous shell - more oxygen, fewer pores, stronger eggs.

Answer 79

Boundaries prevents transfer of either energy or material.

Answer 80

Permits the exchange of energy but not material

Answer 81

Permits the exchange of energy and material

Answer 82

* The Earth has a continuous supply of energy from the Sun. * The Earth's store of materials (excluding small amounts of extraterrestrial material) is finite. * Overall Earth approximates a closed system. * Since life on Earth began, the biologically important elements have been cycled, where elements are transformed from one chemical compound to another and pass through both the biosphere and geosphere. * This process is termed biogeochemical cycling

Answer 83

* Flux is the rate of transfer of matter between reservoirs * Residence time is the duration a given material/matter spends in a given reservoir Residence time = amount in reservoir / flux

Answer 84

* Terrestrial carbon cycle * Short term * Marine carbon cycle * Medium term * Geological carbon cycle * Long term

Answer 85

10¹² kg C or "gigatonne" Corresponds to 10¹⁵ g C or "petagram"

Answer 86

values in 10¹² kg C and 10¹² kg C yr^-1

Answer 87

Remaining 0.2 x 10¹² kg yr^-1 is buried and becomes marine sediment values in 10¹² kg C and 10¹² kg C yr^-1

Answer 88

values in 10¹² kg C and 10¹² kg C yr^-1

Answer 89

The combined biological processes which transfer organic matter and associated elements to depth. It quickly removes carbon from surface ocean and atmosphere and puts it in the deep ocean. Turning off the biological pump would lead to a 200ppm increase in atmospheric CO2 i.e. the biological pump locks away the equivalent of 200ppm of CO2 in organic carbon. The bio pump in the modern ocean is not working at its full capacity. There are parts of the ocean that could have more life, and if these were utilized could increase its capacity by 50%.

Answer 90

1. Small algae called phytoplankton that live in the euphotic zone of surface ocean waters comsume CO₂ by photosynthesis and form organic matter as tissue (carbohydrate) and release oxygen. These tiny particles cannot sink and so cannot transport carbon deeper into the ocean. 2. Phytoplankton is at the bottom of the food chain and so are grazed upon by zooplankton. The excretion produced by zooplankton contains millions of phytoplankton and has now bio-accumulated (bio-packaged) into denser aggregate called marine snow. Marine snow is heavy/dense enough to start sinking. 3. As the aggregate sinks deeper into the ocean it gets acted upon by bacteria. Under the uptake of 1 mole of oxygen, the organic C is decomposed, freeing 1 mole of dissolved CO₂ (DIC) which is then physically mixed and recycled. 4. This carbon flux takes place in the ocean mixed layer (top 100m) In modern oceans only 10% of DIC leaves this loop and only 1% of C_org gets deposited on the sea floor before respiration takes place, but there were times in Earth history when black shales were getting deposited e.g. anoxic events in Mesozoic The amount of C_org getting deposited obviosly effects the climate balance and controls deep water ocean chemistry of O₂, inorganic carbon, and nutrients (the elements marine organisms need for life = C, N, P, Si, Cd, Fe etc.)

Answer 91

* Surface organic matter decends * During its passage to the deep ocean, marine organic matter decomposes in the water column, releasing CO2. * 90% recycled in surface waters * 9% recycled in deeper waters * Around 1% of this organic matter reaches the sea-bed intact * Once incorporated in the sediment, degredation continues - aerobic and anaerobic organisms * 0.1% of the original surface water organic matter preserved. This small proportion of OM is an important leak in the system bc it allows carbon to enter the long term geological C cycle.

Answer 92

* If transport of photosynthetically produced organic matter to the deep ocean continued in isoloation, the surface waters would be stripped of dissolved CO2. * Continuous exchange of gasses between the atmosphere and ocean causes CO2 in surface waters to be replenished. * Activity of phytoplankton can, therefore, affect the composition of the atmosphere as well as the ocean. * Overall, the effect of **drawdown of CO2** from the atmosphere, the photosynthetic fixation of CO2 in surface waters, and the transport of the organic matter to deeper waters is the biological pump.

Answer 93

40 000 000 : 10 000 000 4 : 1

Answer 94

GPP = 120 x 10¹² kg C yr^-1 NPP = 120 x 10¹² - 90 x 10¹² = 30 x 10¹² kg C yr^-1 The likely fate of this NPP carbon is that it will be returned to the atmosphere as CO₂ following respiration by decomposers.

Answer 95

* i) The flux of carbon for land plants is 120 x 10¹² kg C yr-1; the amount in the reservoir is 560 x 10¹² kg C. * Residence time = amount in reservoir / flux = 560 x 10¹² kg C / 120 x 10¹² kg C yr^-1 = 4.6 yrs * ii) The flux of carbon for soil is 60 x 10¹² kg C yr-1; the amount in the reservoir is 1500 x 10¹² kg C. Residence time = 1500 / 60 = 25 yrs * iii) The fluxes in and out of terrestrial biomass are twice that for soil. The residence times for soil, however, are not 2 x soil. * Carbon in soil has 5 x longer residence time. This is bc the soil reservoir is bigger than that for terrestrial biomass.

Answer 96

560 x 10¹² kg / 150 x 10⁶ km² = 3.7 x 10⁶ kg C per km² = 3.7 kg C per m² Although there is much heterogeneity, e.g. contrast tropical rainforest and deserts.

Answer 97

* In deeper water environments water is CO2-rich due to the decomposition of organic matter. * CO2 is more soluble in water at lower T's and higher P's. * The lower T's and higher P's in deep ocean waters will allow them to hold more dissolved CO2 than surface waters. * CO2 dissolved in water forms carbonic acid; water will be corrosive to CaCO3. * Level at which the rate of dissolution of CaCO3 is equal to the flux of material through the water column is called the CCD. * Below this depth, all shells dissolve. * It is for this reason that the deep ocean floor has no CaCO3 sediments.

Answer 98

* Increased CO2 conc.s in the atmosphere would lead to a corresponding increase of dissolved CO2 in the ocean. * Bc dissolved CO2 forms an acidic solution, the average acidity of the ocean would increase and the CCD would shift to a shallower level.

Answer 99

* Atmospheric oxygen levels would increase. * For each carbon atom that enters the rock reservoir, one oxygen molecule is left behind in the atmosphere.

Answer 100

* Nitrification is the production of **nitrate**. * Most soils are **acidic** (mineralization usually leads to high levels of NH₄⁺) * In well _oxygenated_ soils, nitrifying bacteria **oxidise the NH₄⁺ to NO₂^- and NO₃^-** (releasing energy in the process) * Nitrification takes place in two sequential reactions involving bacteria (**Genus Nitrosomonas** and **Genus Nitrobacter**) 2NH₄⁺ + 3O₂ = 2NO₂^- + 2H₂O + 4H⁺ 2NO₂^- + O₂ = 2NO₃^- * Produces _soluble, mobile, oxidising agent_ - nitrate - during **thunderstorms** and at **vents** as well as in oxic environments * NO₃^- can be leached from soils and may move to organic-rich reducing environments (**denitrification**)

Answer 101

* NO₃^- is converted back to **nitrogen gas** * With, minor amounts of N₂O and NO * Process performed primarily by **heterotrophic bacteria** (e.g. Paracoccus denitrificans or various pseudomonads) * Occurs in _organic-rich anoxic_ environments * **Denitrifying bacteria use NO₃^- instead of O₂ during the oxidation of organic matter in reducing environments** * Converts fixed N to atmospheric N2 - these loses balanced by N fixation

Answer 102

* Nitrification-denitrification cycle * Soil well aerated at surface * Shallow organic N converted to nitrate * Much leached from the soil * At depth, soil waterlogged and anoxic * Nitrate washed in from above * Denitifying bacteria e.g. *Pseudomonas* * Oxidize the organic matter using nitrate instead of oxygen * End products are N₂, N₂O and NO

Answer 103

* Digestion is the **mechanical and chemical breakdown** of food into smaller components that are more easily **absorbed** into a bloodstream * **Peptide bonds** of that link the amino acids of the injested proteins together are broken and individual **amino acids** are released. * Some amino acids are used to make **proteins** and _repair damaged tissues_, and excess protein is an _energy source_. * During **mineralization**, amino groups are removed and the carbon skeletons are catabolized to CO₂ and water. * Then, nitrogen is released initially as **NH₃**, this molecule is rapidly converted to **NH₄⁺**. * NH₄⁺ can be **toxic** and its removal requires water. * Aquatic organisms dissolve it away, and most mammals (including humans) convert it to **urea**, CO(NH₂)₂. * Birds, reptiles and insects produce insoluble **uric acid** C₅H₄N₄O₃ (guano, fertilizer)

Answer 104

* Decomposes to NH₃ and CO₂ * CO(NH₂)₂ + H2O → 2NH₃ + CO₂ * NH₃ lost to atmosphere * Process may be very common on arable land * Manures and animal slurries can lose up to half of their nitrogen by ammonia volitization

Answer 105

* Fixation is the first step in the nitrogen cycle * For use in growth N must be "fixed" or *combined*: * Ammonium (NH4+) ions * Nitrate (NO3-) ions * Urea [CO(NH₂)₂] * Plants secture their N in fixed form through *assimilation.*

Answer 106

Even though there is abundant N in Earth's atmosphere, nearly 79% is in the form of N2 gas. N2 is unavailable for use bc of strong triple bond making the molecule almost inert. N is often the limiting factor for growth.

Answer 107

* N is difficult to fix, but * Plants must secure their N in "fixed" form through assimilation. * Animals secure their N compounds from plants (or animals that have fed on plants) * Weathering of rocks is slow (negligible effect on the availability of fixed N)

Answer 108

* Small amount of ammonia is produced by **lightning**. * Small amounts at **volcanic vents** (conventional thought) * Ammonia also produced industrially by the **Haber-Bosch process** * Major conversion of N₂ into ammonia achived by **microorganisms** (_biological fixation x2 non-biological_)

Answer 109

* Lightning produces 1,000-100,000 Amps and reaches 30,000°C in its less-than-half-a-second duration. * Produces more energy than all of the electrical utilities in the world combined during that instant. * Splits triple bond in N₂ (N₂ + O₂ → 2NO) and N is rained out in nitric acid. * 10 x 10¹² g yr^-1 fixed N. * Important prebiotic source of fixed N.

Answer 110

* Volcanic vents promote the thermal fixation of atmospheric N₂. * At Masaya volcano, Nicaragua, NO and NO₂ are present in volcanic aerosols * NO_x levels are an order of magnitude above background. * HNO₃ contents are elevated. * Present-day global production of fixed N at hot vents = 14 x 10¹⁰ g yr^-1 * Potentially important source of fixed N on the early Earth

Answer 111

* Conversion efficiency would have been lower in a non-oxygenated atmosphere * More subaerial volcanism

Answer 112

* 1.4 x 10¹² g yr^-1 of fixed N during major episodes of volcanism * Comparable to nitrogen-fixation rates from lightning

Answer 113

* Ability to fix N is found only in certain bacteria * Some N-fixing bacteria live free in the soil * Some live in a **symbiotic relationship** with plants of the legume family (e.g. soyabeans, alfalfa) * Some establish symbiotic relationships with plants other than legumes (e.g. alders) * **N-fixing cyanobacteria** are essentially for fertility of semi-aquatic environments, e.g. rice paddies * Biological N-fixation **requires a complex set of enzymes and a huge expenditure of energy**. * First stable product of the process is **ammonia (NH₃)**, this is quickly incorporated into **proteins** and other organic nitrogen compounds.

Answer 114

A close association between two distinct species where both organisms benefit from the relationship

Answer 115

* Every plant in the **Lower Sonoran desert** in Arizona depends on biological N fixation. * Free-living cyanobacteria associate with **lichens**. * Contribute N to the soil by forming a **cryptobiotic crust** (delicate, thin, fibrous, biological soil crust) * Leguminous plants followed (N-fixing *Rhizobium* in their root nodules) * E.g. *Parkinsonia sp.*

Answer 116

* **Haber-Bosch** process * Hydrogen is first obtained from natural gas (methane) * Ni catalyst * 30 atmospheres * 750°C * CH₄ + 2H₂O → CO₂ + 4H₂ * Nitrogen and hydrogen are then reacted to produce **ammonia** * Iron catalyst * 200 atm * 450°C * N₂(g) + 3H₂(g) ⇔ 2NH₃(g) + heat

Answer 117

* Haber-Bosch products represent **fertilizers from non-natural sources** (agriculturally significant) * Considered the most important invention of the 20th Century bc it **initiated population explosion** (**_1.6_** billion in 1900 to **_6.0_** billion in 2000) * _1%_ of the world's present-day energy supply is used for Haber-Bosch process, producing _500 million tons of artificial fertilizer per year_. * This sustains roughly **40% of the population**!!

Answer 118

* Ozone (O₃) is a highly reactive and toxic gas located in the very stable stratosphere. * Most (~90%) of ozone is in the stratosphere between 10-16 km up to ~50 km altitude. * Most ozone resides in an "ozone layer" 15 - 30 km altitude. * The remaining ozone (~10%) resides in the troposphere, the lowest region of the atmosphere.

Answer 119

* Measure amount in a column of atmosphere directly above a point at Earth's surface. * Measured using a **Dobson spectrometer**. * Expressed in **Dobson units (DU)**. * Ozone _absorbs UV light_ but does not absorb visible light. * Amount of ozone in the atmosphere determined by **measuring the difference between the two wavelengths**.

Answer 120

* Detected by aircraft and satellites in contact with ozone * **UV absorption** * Electrical currents generated by chemical reactions involving ozone. * Small balloons or aircraft travel to required locations, transporting measuring devices (**ozonesondes**)

Answer 121

* **Sidney Chapman** deduced reactions for production and destruction of atmospheric ozone. * Ozone production begins when an _O₂ molecule is broken apart_ by light *(hv)* * UV radiation with _wavelenghts \< 240 nm_ * Process termed **photodissociation**. O₂ + *hv* → 2O * _O atom combine with another O₂ molecule_ to produce ozone (note: lifetime of O very short in the stratosphere, typically \< 1 s) O + O₂ → O₃ * Amount of energy generated by the collision is too much for the newly formed ozone molecule, so * A **helper molecule, M**, which can be any other atmospheric gas removes excess. O + O₂ + M → O₃ + M

Answer 122

* Ozone is a strong absorber of light between 240 and 310 nm (energy absorbed and released as heat). O₃ + *hv* → heat * However, with wavelengths above 310 nm, ozone is dissociated to an oxygen atom and molecular oxygen. * This reduction also gives out heat. O₃ + *hv* → O + O₂ * We are now back to the raw materials of ozone generation. O + O₂ → O₃

Answer 123

* Chapman realized photochemical production and destruction of ozone is a cyclic process. * Cycle stops when a fourth reaction occurs. * Ozone molecule meets single atom of oxygen * Two stable molecules of O2 are formed * Overall, natural ozone loss should balance production.

Answer 124

* Stratospheric ("good") ozone absorbs UV-B radiation from the Sun. * Therefore, there is a negative correlation between the two factors: high amounts of UV-B at the surface = low amounts of stratospheric ozone and v.v. * In the 1970's numerical models and lab. experiments discovered 30% less ozone in the stratosphere than predicted. * Depleted by increased rate of ozone destruction: * Raised conc.s of ozone-depleting molecules in the stratosphere. * Ozone-depleting molecules (X) disturb the ozone cycle. * Net change is a loss of ozone.

Answer 125

X + O₃ → XO + O₂ XO + O → X + O₂ Net change: O + O₃ → 2O₂ * X is not included in the net reaction bc it is a catalyst * Trace amounts of X can remove large quantities of ozone bc it is continually recycled

Answer 126

A substance which increases the rate of reaction but remains unchanged at the end

Answer 127

* **NO** ; major source = supersonic jet aircraft * CFC's e.g. **CFCl₃ (Freon-11)** ; refrigerant, propellant * BFC's e.g. **CF₃Br (Halon-1301)** ; fire extinguisher

Answer 128

* Indirectly from biological N2O * Accelerated by the application of agricultural fertilizers * Directly from supersonic aircraft

Answer 129

* CFC's reach the stratosphere and decompose to release chlorine radicals that catalytically destroy ozone * BFC's have similar effect

Answer 130

1. The ozone hole is largely an Antarctic phenomenon. 2. The ozone hole occurs only during October. 3. The ozone hole did not exist prior to 1967.

Answer 131

* Stratosphere is relatively isolated from adjacent areas during the winter months * Cold, dense air sinks in a polar vortex * Wind speeds are much higher than the surrounding atmosphere * Transfer of gas into the Antarctic stratosphere is very limited * Any ozone depletion which occurs cannot be replenished from other parts of the Earth's stratosphere

Answer 132

* Very low T's during May to September * Clouds generally confined to the troposphere * Stratosphere over Antarctica is so cold (less than 80°C ???) that small amounts of nitric acid and water freeze out. * Reactions occur that involve molecules in both the gas phase and solid phase. * They are termed **heterogeneous reactions**.

Answer 133

* In the stratosphere chlorine and nitrogen containing molecules combine to form a reletively **unreactive** compound - Chlorine nitrate or **ClONO₂**. * ClONO₂ does not react easily with ozone or oxygen, but forms an **inert store of Cl and NO**. * For this reason, it is often termed a "**reservoir compound**". * On surfaces of polar stratospheric particles, however, **heterogeneous reactions** can release chlorine. * ClONO₂ and HCl react on the **surfaces of the ice particles**, leading to the **production of Cl₂**. * Cl₂ itself will not destroy ozone, but conversion of Cl₂ to **Cl radicals** _determines the timing of ozone hole_. * Cl₂ remains frozen in the stratospheric particles until the **Antarctic spring in October**. * Levels of sunlight increase and the Cl₂ is released and **photodissociated** to form chlorine radicals. * They begin a **catalytic cycle** of ozone destruction.

Answer 134

Cl has anthropogenic origin, hence 1976 origin of ozone hole.

Answer 135

* Ozone is derived from atmospheric oxygen, and oxygen built up around 2 Ga during the Great Oxidation Event. * Only small amount of oxygen needed * Ozone production has **non-linear** relationship with oxygen conc. * **Photochemical models suggest 100 DU at 0.001 PAL** * Decent Ozone layer present at **2.3 Ga**

Answer 136

* The **Fungal spike** (fungal event) * Unique abundances of fungi * Coincident with isotope shift * **End-Permian** bioevent * Worldwide * All environments * Destruction of terrestrial biomass (_gymnosperm forests_) * Replaced by **opportunistic herbs** (e.g. 1-2 m tall ***Pleuromia*** - a _spore producing_ lycopod) * Fossil evidence in **early Triassic Red Sandstone** of the **Eifel area, Germany**.

Answer 137

* Modern day example is the contaminated area of the **Black Triangle**, Great Mountains. * Boundary between Germany, Poland, Czech Republic. * Where buring of **black coal** (**sulfur-rich lignite**) led to the release of **sulfur dioxide (SO₂)** and **nitrogen dioxide (NO₂)** led to the production of **acid rain (nitric acid)**. * Between _1972 and 1989_, **50% of coniferous forest died** (50% of children born also died). * Deforestation led to *opportunistic* **expansion of lower vascular plants** and **_proliferation of fungi_**. * Extinction = loss in diversity = dominated by _opportunistic herbs_ / _decomposers dominant_ over others that don't survive in low pH conditions.

Answer 138

* The morphology of End-Permian **lycopsid microspores** tell us something of the possible mechanism. * Tetrads normally seperate following dispersal, * However, during the E.P., tetrads dispersed **intact**, with no seperation - and this occured _worldwide_. * It is seen that the prevention of tetrad **pectin** (plastic) **degredation** caused by **gene mutation** from **radiation damage** was the cause. * *But what was the source of radiation? Cosmic radiation, or depletion of ozone in some way? See next card...*

Answer 139

* *Cosmic radiation* could be a good source, but only lasts 10-100s years - **too short** for the End-Permian. * Maybe an *impact* could have destroyed the ozone layer by punching a hole through it? * **Helium** and **osmium** show _terrestrial values_. * No conclusive evidence for impact (e.g. no shocked quartz) * **_Siberian traps_ viable option**, the largest Phanerozoic volcanic event, associated with _massive emissions_ and _aerosol_ release and _acidification_.. * **Hydrothermalism** *(heat + water)* of **halogen-rich country rocks** (evaporitic sed. basin) (organohalogens) over **500 kyrs**, leading to **ozone depletion** and **UV-B increase** and _gene damage_. * Followed by **ecosystem destabalization**, loss of rooted vegetation and soil erosion. * Affected _carbon cycle_.

Answer 140

* **UV-B radiation** (280-315 nm) **damages** plant proteins, membrane lipids DNA and can cause mutations. * But as plants need **sunlight for photosynthesis**, they face a _trade-off_ between UV-B exposure and the need for photosynthesis. * One way around this imbalance is the **use of UV-B absorbing compounds**: * Sporopollenin, structural contituents of outer walls of pollen and spores from vascular plants. * **Aromatic acids absorb in the UV-B range**. * Aromatic acids - **UV pigment abundance _proxy UVB flux_**. * Results show that ozone has been decreasing with time since ~1960 at high latitudes.

Answer 141

* Small continents result in little silicate weathering and **small land storage**, small carbonate stores. * **Atmosphere, ocean and sea floor primary reservoirs**. * _More dissolved inorganic C_ (in atmos. + ocean) during the Hadean, with _higher heat flux_ and ideal conditions for forming _carbonated basalts (carbonites)_ (water pumped through vents). * Interaction between ocean and atmosphere so regular that they have an equal proportion of carbon. * Assuming no land storage: * **Carbon 6:1 - seafloor:ocean**, * T.f. **1/7 (15%) present in atmosphere and ocean, relative to sediments**.

Answer 142

* Taking simple C cycle assumptions: * Assume no continents so no land storage. * Atmosphere, ocean and sea floor only reservoirs. * _Assume 100% efficiency for carbon removal in vents_. * Seafloor lifetime 60 Myrs; ocean through vents in 10 Myrs * 10²⁰ kg surface carbonate 4.5 Ga (assume same as today) * Carbon **6:1** - seafloor:ocean * **1/7 (15%)** present in _atmosphere + ocean_ * **0.15 x 10²⁰ kg** = 1.5 x10¹⁹kg * C_atmos = C_ocean = 7.5 x10¹⁸ kg (**1.5 x10¹⁹ / 2**) * C_sea.sed = **0.85 x 10²⁰** = 8.5 x10¹⁸kg

Answer 143

_Carbonica_ * Carbon 6:1 - seafloor:ocean * 1/7 (15%) present in atmosphere + ocean * **0.15 x 10²⁰ kg = 1.5 x10¹⁹ kg** * Catmos = Cocean = 7.5 x10¹⁸ kg (1.5 x10¹⁹ / 2) * Csea.sed = 0.85 x 10²⁰ = 8.5 x10¹⁸ kg _Present-day Earth_ * 4 x10¹⁶ + 7.6 x10¹⁴ (ocean + atmosphere) * 4.076 x10¹⁶ kg = **4.1 x10¹⁶** * Carbonica(/Hadean) has **_~400 (365.9)_** times more CO₂ * The effect = **substantial greenhouse effect**

Answer 144

* Photosynthesis * light + nCO₂ + nH₂O → (CH₂O)n + nO₂ * Light is harvested and converted to energy stores * Respiration * (CH₂O)n + nO₂ → nCO₂ + nH₂O + energy * Energy store is consumed to drive biochemical reactions * Balanced equations = only energy is consumed

Answer 145

no answer in notes

Earth Systems Flashcards

(175 cards)