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EOS > EOS 260 Part II > Flashcards

EOS 260 Part II Flashcards

1
Q

OILRIG

A

oxidation is loss, reduction is gain

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2
Q

geochemical oxidation states

A

doesn’t work to think of electron gain/loss in terms of reservoirs, must think of oxidation state in terms of compounds in them

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3
Q

Oxidation states of H

A

Reference species- H2O

Reduced- H2

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4
Q

oxidation states of C

A

reference species- CO2

reduced- CH4, CO

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5
Q

oxidations states of S

A

reference species- SO2
Reduced- S8
Oxidized- SO4 (2-)

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6
Q

fugacity

A

pressure value needed at a given temperature to make the properties of a non-ideal gas satisfy the equation for an ideal gas

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7
Q

used to infer oxygen fugacity from stable minerals

A

mineral redox buffers (ex. hematite-magnetite), in equilibrium at given oxidation state

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8
Q

oxidation states of iron

A

Fe (2+)- Ferrous, reduced, ex. mineral- wustite, FeO, soluble in water; Fe (3+)- Ferric, oxidized iron, ex mineralogy- hematite, Fe2O3, insoluble in water

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9
Q

magnetite

A

Fe3O4- mixed valence

i.e. FeO•Fe2O3

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10
Q

In a reducing atmosphere

A

lots of CH4, CO (reduced molecules)

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11
Q

evidence for redox state

A

geological indicators: reduced/oxidized minerals

modern geochemical evidence

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12
Q

geological indicators of redox state

A

redbeds
banded iron formations
certain detrital minerals
minerals in palaeosols

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13
Q

modern geochemical evidence of redox state

A

sulphur isotopes
trace metal abundances ex. (Mo)
Cr isotopes

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14
Q

Redbeds

A

detrital sed. rocks (lots of sandstone), with ferric (oxidized) Fe, form through subaerial alteration- deposited in air with lots of O2 available

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15
Q

Redbeds occur

A

only after ~2.3Ga

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16
Q

BIFs

A

alternating layers of magnetite/hematite and chert, deposited in anoxic H2O column, sedimentary rock

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17
Q

BIF sedimentation

A

ferrous Fe released at MOR– dissolved, transported in anoxic ocean– ferric precipitates where oxidation occurs; form major iron ores

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18
Q

indicator of oxygen

A

redbeds

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19
Q

anoxic oxidation

A

4Fe(2+) + CO2 + 11H2O +hv —- 4Fe(OH)3 + CH2O + 8H+

reducing power transferred from Fe(2+) to CH2O

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20
Q

BIF occurrences

A

frequency vs. years ago

1.5-4bya, mostly Precambrian (Archean), some proterozoic

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21
Q

Hamersley BIF

A

2.69-2.44Ga
deposition- 5x10^11 mol Fe/yr
1.25x10^11 mol O2 equiv. /yr
globally may have been 6X this

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22
Q

detrital uraninite

A

Archean U ores commonly detrital, imply anoxic event- UO2 would have oxidized and dissolved

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23
Q

detrital

A

deposited by rivers

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24
Q

mass-independent fractionation of S isotopes

A

requires photolysis by UV, which requires lack of ozone layer, which means lack of O2

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25
Q

S weird behaviour

A

δ33S, δ34S, different behaviours, increased weird behaviour ~2.5Ga, large increase in Δ33S ~2.5Ga

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26
Q

Ga =

A

billion years

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27
Q

S escape pathways

A

S8, SO2– need to get both forms out of atmosphere

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28
Q

most important geochemical change in history

A

anoxic- oxic atmosphere

reducing- oxidizing

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29
Q

oxygen level vs. age (Ga)

A

up to 2.5Ga- oxygen ~1ppb, MIF constraints, ~2Ga significant increase in O2 levels

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30
Q

present oxygen atmosphere

A

21% O2

3.7x10^19 mol O2

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31
Q

moles in atmosphere

A

1.8x10^20 mol

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32
Q

reserving oxygenic photosynthesis

A

respiration:

H2O + CO2– CH2O + O2

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33
Q

how to get O2 into atmosphere

A

Bury organic carbon in rocks- net oxygen source

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34
Q

marine productivity

A

103PgC/yr

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35
Q

burial flux

A

0.1PgC/yr

~10^13 mol/yr

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36
Q

total BOC

A

~10^21 mol, 25X the O2 in the atmosphere

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37
Q

accounting for oxidation

A

oxidants: in sediments (0.5), excess Fe3+ in igneous rocks (2.5)
reductants: reduced C in crust (~1.5), missing reductant (~1.5)

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38
Q

where is the rest of the O2

A

hydrogen escape

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39
Q

Hydrogen escape

A

H light- escapes atmosphere– oxygen source (splitting water)

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40
Q

photolysis of H2O

A

2H2O + hv — 4H(to space) + O2

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41
Q

hydrogen escape from H2O rich atmosphere

A

excess H2O in upper atmos. + energy source– hydrodynamic escape
energy limited
loose ocean worth of H in few hundred million years

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42
Q

hydrodynamic escape

A

hydrogen literally flows out

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43
Q

energy source for hydrodynamic escape

A

EUV- extreme UV radiation

limits rate of escape

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44
Q

hydrogen escape from normal atmosphere

A

H2O cold trapped at tropopause, diffusion limited, CH4 major H-bearing species, rate is small

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45
Q

normal atmosphere, ‘diffusion limited’

A
  • total hydrogen mixing ratio: fH_total = 2fH2O + 4fCH4 +… very small
  • buoyancy of light atoms above homopause
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46
Q

hydrogen escape rate from normal atmosphere

A

~10^10 mol O2/ yr

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47
Q

The Great Oxidation

A

~2.4Ga, reducing-oxidizing atmosphere, ~1ppmv-1% O2, biggest chemical transition in Earth history, changes in glaciation

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48
Q

bad hypotheses

A
  • GO followed oxygenic photosynthesis (2.7Ga)

- there has always been high O2 in atmosphere

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49
Q

great oxidation box model

A

atmos/ocean reservoir of O2, CH4 flux between organic carbon
also—> hydrogen escape = constant x CH4
also<— volcanic gases, reduced Fe from mantle

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50
Q

conceptual model of the environment, pre-GO

A

anoxic atmos./ocean, stromatolite reefs– oxygenic photosyn.– sinking organic matter (requires decay path)

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51
Q

anoxic decay path for organic matter

A

fermentation followed by methanogenesis (methane formation)

2CH2O — CH4 + CO2

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52
Q

processes

A
  1. Primary Productivity
    2i. Aerobic respiration
    2ii. Methanogenesis
  2. Atmospheric chemistry- methane oxidation
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53
Q

Methane oxidation

A

Net rxn: 2O2 + CH4 — 2H2O + CO2

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54
Q

methane oxidation rate constant

A

depends on OH availability

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55
Q

OH availability

A

produced by footless of H2O by UV
mostly deep in troposphere
depend on UV penetration to troposphere

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56
Q

UV photons today

A

attenuated in stratosphere by O3

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57
Q

bistability in atmospheric oxygen

A

Balanced (O2 + 1/2CH4) source— fast methane oxidation

or— slow methane oxidation

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58
Q

fast methane oxidation

A

low oxygen– no ozone– UV to troposphere– OH abundant– fast methane oxidation– low O2

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59
Q

slow methane oxidation

A

high oxygen– ozone layer– UV blocked— not much OH— slow methane oxidation– high O2 (can accumulate)

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60
Q

bistability graph

A

oxygen vs. NPP (input)
low O2 level stability– form O3 layer– ‘flip up’ to high O2 stability
instability in middle

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61
Q

closed cycle

A

production of methane and oxygen — atmospheric chemical destruction

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62
Q

to support reducing atmosphere

A

need strong flux of reductants (Fe2+) to ‘tip the balance’ (of the closed cycle)

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63
Q

rate of hydrogen escape depends on

A

fH_total, depends on reductant input; more reducing atmos. = faster planetary oxidation

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64
Q

high oxygen stability

A

more stable state

once high oxygen is reached, unlikely it will be lost

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65
Q

GO biochemistry

A

metabolisms, NPP

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66
Q

GO atmospheric chemistry

A

methane oxidation

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67
Q

GO upper atmosphere physics

A

hydrogen escape

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68
Q

GO aqueous chemistry

A

iron solubility

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69
Q

GO sedimentary geology

A

evidence for oxidation states

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70
Q

FYSP

A

faint young sun paradox- contradiction between observations of H2O_l early in Earth’s history, and Sun’s output only 70% as intense

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71
Q

Ice cover on Earth since 3Ga

A

globally- small periods in proterozoic, most of cryogen
regional- mostly Devonian- Permian
before 3.0Ga- not enough records

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72
Q

S 4.5bya

A

0.7S
Quasi-linear increase through time
feature of main sequence of stellar evolution

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73
Q

Energy deficit

A

σT^4 = (1-α) S/4
ΔF_s = (1-0.3)(1368/4)(1-0.8) = 50W/m^2
but no record of it being cold.. had to be warmer than today?

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74
Q

neoarchean S =

A

0.8S_o

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75
Q

deficit in solar forcing balanced with

A

radiative forcing
CO2
CH4
other GHGs

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76
Q

CO2 radiative forcing vs. concentration

A

50W/m^2 would require 80,000ppm

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77
Q

paleosols

A

fossilized soil in contact w/ atmos., look at mineral assemblage to determine if they could have been present w/ different CO2 levels

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78
Q

palaeosols show

A

10-100pCO2 at 2.5Ga ?

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79
Q

Methane radiative forcing

A

100ppm of CH4 gives 8-15W/m^2, not enough forcing

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80
Q

CO2 + CH4 forcing

A

~40W/m^2– need another 10

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81
Q

the missing F

A

turn up N2– pressure broadening

green line in graphs = 2XN2_atm levels– CO2 has higher forcing

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82
Q

pressure broadening

A

more molecules = more pressure = more molecular movement (more collisions with radiation)

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83
Q

measuring pressure in past

A

paleobarometer

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84
Q

methods for measure pressure in past

A

fossilized rain drop imprints (tell density)

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85
Q

other proposals for ‘the other 10’

A

mixture of other GHGs- ammonia, OCS, clouds

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86
Q

clouds

A

high clouds have strongest greenhouse effect– more low clouds? – very unknown

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87
Q

when is the cryogenian

A

650-750Ma, neo-proterozoic (top of the proterozoic)

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88
Q

importance of Cryogenian

A

extensive, Snowball Earth glaciations (pole-pole)
lead into second oxidation event
evolution of animals around this time

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89
Q

2 glaciations in cryogenian

A
  1. Sturtian (longer)

2. Marinoan

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90
Q

pole-pole glaciation

A

large ice cap instability (past ~30º)

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91
Q

sturtian timing

A

onset: 710-720 Ma
termination: 655-655 Ma
duration: 58Myr

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92
Q

Marinoan timing

A

onset: 640-660Ma
termination: 630-640Ma
duration: 4-14Ma

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93
Q

dating glacial onset/termination

A

O isotopes- get ‘reset’

U-Pb- volcanic ash right below/above glacial sediment

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94
Q

sedimentary record of a glacier

A

glaciers erode and deposit

produce variety of sediments/structures

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95
Q

glacial environment

A

ice– out wash plain

below ice– glacial till

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96
Q

post-glacial environment

A

till plain– terminal moraine– pitted outwash plain

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97
Q

till

A

very poorly sorted sediment ranging in size from very fine grained to giant boulders

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98
Q

glacial deposits

A 
till
striated clasts
glacial pavement
dropstones
polygonal sand wedges
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99
Q

glacial pavement

A

striations/grooves/chattermarks in bedrock

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100
Q

chattermark

A

something in bottom of glacier sticks for a bit then moves.. stick– move–stick–move

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101
Q

dropstone

A

glacier near body of water– iceberg– iceberg drops debris; warp layered beds; can cause folding (if high force)

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102
Q

glacial deposits

A

mostly around glacier margins

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103
Q

glacial movement

A

very dynamic, move all over the place all the time

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104
Q

polygonal sand wedges

A

freeze/thaw cycles at edge of glacier; ground water– ice– crack sed.– fill w/ sand– propagates; same shape as mud cracks, columnar joint

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105
Q

Importance of glacial deposit present locations

A

paleogeography, paleomagnetism– determining where continents were– determining if glaciation was low latitude

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106
Q

Paleomagnetism

A

rocks contain minerals w/ magnetic properties that align themselves w/ Earths dipole magnetic field; which way lines point- which way was up– determine paleo

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107
Q

flow/field lines

A

parallel to surface at equator

perpendicular to surface at pole

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108
Q

general cryogenian strat section, bottom up

A

coarse grain clastics– deep water carbonate– shallow water carbonate– fine grained clastic– glacigenic diamictice– DWC– SWC– glycogenic diamictice– DWC– SWC

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109
Q

in between glacial units (glacigenic diamictite)

A

we see carbonate– implies low latitude

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110
Q

diamictite

A

sedimentary rock that consists of a wide range of lithified, nonsorted to poorly sorted, terrigenous sediment, i.e. sand or larger size particles that are suspended in a mud matrix

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111
Q

Cryogenian BIFs

A

reappear in cryogenian after ~1Ga- dramatic drop in oxygen levels ~2-1bya- lower productivity

112
Q

cap carbonates

A

unique facies found only after snowball earth glaciations; imply very rapid deposition post-snowball; deepening upward progression of facies (transgression)- CUS, finely laminated, mostly parallel

113
Q

cap carbonate sequence

A

pre-glacial carb.– tillite– dolomite (dolostone, stromatolites, giant wave ripples, bariite)– limestone

114
Q

piercing points

A

align split up formations- large basalt beds, large deformation belts

115
Q

diamictite overlying carbonates

A

weird, till-cold, carbs-warm

116
Q

commonly seen cap carb ‘package’

A

carb.–diamic–cap carb–carb platform– diamic–cap–carb–shale–till

117
Q

carbonate platform

A

low latitude

118
Q

fine sedimentfrom

A

slow rain out of ice shelf into underlying water

119
Q

cap carb stromatolites

A

narrower, sharper than usual– indicate shallow water

120
Q

types of low-latitude glaciation

A

hard snowball- thick (700m) over all oceans

open water- slushball, or Jormungand

121
Q

Jormungand

A

thin belt of water around equator- ablation zone- old ice at tip of glacier- dirty, lower albedo

122
Q

slushball

A

low-lat continental glaciation but sea-ice instability not reached

123
Q

ice stability graph

A

stable state at ~10º, some open water

124
Q

initiating a snowball

A

must lower CO2, reduce GHGs, decrease source, increase sink

125
Q

decreasing GHG source

A

lower volcanism

126
Q

increasing sinks

A

weathering, rock formation

127
Q

silicate weathering feedback

A

negative feedback; temperature dependent; million year timescale
CO2 + CaSiO3— CaCO3 + SiO2
forward rxn: weathering
backward rxn: metamorphism

128
Q

lichen evolution

A

increased weathering (acids), photosynthesis, change albedo; CO2 draw down, more nutrients to ocean– further CO2 drawdown

129
Q

continents were at low latitudes

A

increasing albedo– increases Earth albedo (majority of insolation)– increases weathering

130
Q

Franklin LIP

A

large basalt eruption, low latitude Large Igneous Province, easily weatherable- large CO2 sink, glaciation driver

131
Q

continental area <15º latitude (%)

A

~25% at onset of glaciation (~5% 100Ma before that)

132
Q

evidence of increased basalt weathering

A

Sr isotopes; decreases in 87Sr/86Sr before each of the glaciations

133
Q

solar radiation absorbed

A

F_SW = (S/S_o)(S_o/4)(1-α)

134
Q

Present day F_SW

A

239 W/m^2

135
Q

deficit in solar radiation, and amount of CO2 needed to have a mean surface T equal to today, todays albedo

A

(0.94)(1368/4)(1-0.3) = 225W/m^2
∆F = 14W/m^2
~2-3000ppv CO2

136
Q

deficit in solar radiation, and amount of CO2 needed to have a mean surface T equal to today, low lat. glaciation albedo = 0.6

A

F = 129 W/m^2
∆F = 110W/m^2
>1,000,000ppv CO2 (1bar) ?

137
Q

300ppmv =

A

3x10^-4 ppv

300x10^-6 ppv

138
Q

deglaciation requires

A

mean surface T 0ºC

139
Q

∆T =

A

(alpha)(Forcing)

140
Q

climate models require

A

0.1bar CO2 to exit snowball earth

141
Q

cap carbonate problem

A

absence of primary carbonates during glaciation

fast deposition of thick cap carbonates following deglaciation

142
Q

old thinking of cap carbonate

A

hard snowball– no air-sea gas exchange– volcanic CO2 accumulates in atmosphere– ice melts– CO2 invades ocean– flux of alkalinity from rapid weathering– cap carb deposition

143
Q

enough CO2 to initiate warming and ice-albedo feedback

A

F = 90W/m^2
0.5bar CO2
very close to models for rudimentary calculations, see if you can get these answers

144
Q

problem with old thinking of cap carbonate problem

A

most likely some air-sea gas exchange taking place

145
Q

new thinking of cap carbonates

A

gas exchange allowed– atmos. ocean equilib– warming w/ deglaciation– CO2 flux from O-A– decrease DIC– speciate toward CO3(2-)– higher Ω– higher carbonate precipitation

146
Q

why no carbonate deposition

A

lower sea level– no suitable depositional environment

147
Q

to deposit more carbonate; DIC vs. CO3(2-)

A

have to move to higher CO3(2-) or lower DIC, generally diagonally down to the right

148
Q

was the ocean acid or neutral during glaciation

A

2 competing hypotheses
Acid- CO2 influx w/ no Alk flux
Neutral- continued Alk flux

149
Q

which hypothesis is right? (acid or neutral)

A

likely somewhat acidic

DIC vs. pCO2— higher pCO2, regardless of Alk we are in the higher portion of the graph

150
Q

Nitrogen discovered by

A

Daniel Rutherford, 1772

151
Q

nitrogen rich air

A

Noxious, Mephitic air

152
Q

how N was discovered

A

box of air w/ candle, candle absorbs O2, mouse in box, dies

153
Q

N cycles

A

biologic - fast, dominates in short periods of time

geologic - slow

154
Q

N characteristics

A

5th most abundant element in the solar system;

2 stable isotopes: 14N 99.634%, 15N (0.366%); geochemically flexible, lots of redox states, lots of transformations

155
Q

nitrogen oxidation states

A 
oxidations state and species
V, NO3(-) **abundant
III, NO2(-)
II, NO
I, N2O
0, N2 **
-I, NH2OH
-II, N2H4
-III, NH4 **
156
Q

N species most important for ocean biology

A

NO3

157
Q

N2 in the atmosphere

A

dominant gas, 78%

158
Q

N as a nutrient

A

very important, key ingredient in amino acids; triple bond very strong, requires lots of energy, limiting nutrient

159
Q

fixing

A

breaking triple bond and incorporating N into biomolecules, N2– NO

160
Q

natural N fixers

A

lightening (minor)- 5 Tg/yr

bacteria (major, dominant)- 252 Tg/yr, ~equal btw ocean/land

161
Q

anthropogenic N fixing

A

Haber-Bosch process

make NH3 for fertilizer and explosives

162
Q

N is fixed by using

A

nitrogenase enzyme

metal cofactors

163
Q

metal cofactors

A

Fe-Mo (most efficient)
Fe-Fe
Fe-V less efficient

164
Q

N sources before Haber-Bosch

A

gauno

165
Q

Haber-Bosch

A

Fritz Haber, 1909; industrialized by Carl Bosch; react N2 with H2 at high pressure– NH3; 140 Tg/yr; may have extended WWI; has pushed N cycle way out of equilibriumm

166
Q

N fixing reaction

A

N2– PN

particulate nitrogen

167
Q

ammonification

A

PN– NH3 or NH4(+)

168
Q

nitrification

A

NH4(+) — NO3(-)

bacterially mediated

169
Q

organisms prefer N in what form

A

NH4(+)- easiest to incorporate

NO3(-) is most abundant bioavailable

170
Q

denitrification

A

NO3(-)—- N2 or N2O

bacteria using NO3 in electron transport chain

171
Q

largest N flux out of the ocean

A

denitrification - 240 Tg/yr

out of balance with input

172
Q

known planets orbiting stars

A

~2000

173
Q

NASA, Kepler

A

watches one portion of sky constantly for dips in output radiation of stars (planet going in front of star)

174
Q

beginning of Gaia hypothesis

A

mars exploration

175
Q

disequilibrium in earths atmosphere

A

due to life

176
Q

indicate life

A

persistence of unstable gases in atmosphere

ex. CH4 only last ~10yrs: ice cores show ~500,000yrs of CH4

177
Q

early mars

A

features indicative of flowing water but no atmosphere; mars has no plate tectonics; dead planet

178
Q

how to find life

A

check atmos. composition for equilibrium by using slits to spread light (spectroscopy)

179
Q

what you will see on a planet with no atmosphere

A

theoretic Planck function

180
Q

determining presence of atmosphere, start with

A

water; life as we know it is water dependent; less sunlight in, less IR out ≠ planck function, greenhouse effect

181
Q

also look for

A

CO2, O2, O3, CH4

‘weird’ spectrums may equal life

182
Q

a slice in time?

A

must look at whole earth history– Archean biosphere had very little O2 even with life

183
Q

nitrogen cycle

A

Atm N2—dissolves ε=(-)0.6‰—N2—N fixing ε=0— PN—Ammonification ε=3‰— NH4—- Nitrification ε=+7‰ — NO3– Denitrification ε=25‰— N2— Atm N2

184
Q

Denitrification ε

A

= 25‰

enriches light isotope use– heavy isotopes left behind

185
Q

denitrification occurs

A

at boundary between oxic and anoxic layers

186
Q

Tg

A

10^12

187
Q

δ15N in plants on various substrates

A

N-rick substrate (schist): δ15N_plant = δ15N_rock

N-poor substrate (granite): δ15N_plant < δ15N_soil < δ15N_rock

188
Q

plant growth vs. δ15N_plant

A

increasing δ15N = increasing growth; δ15N > 0 are all spawning sites– salmon bring in isotopically heavy N; δ15N_ocean > δ15N_land

189
Q

anthropogenic climate change and N use on the N cycle

A

land-use change– atmospheric CO2, PP
FF burning– atmosph. CO2, N– climate warming– everything
Industrial N fixing- biologically available
large impacts, overall effects unknown- also increase weathering, release rock NH4

190
Q

δ15N and age, vs. [N]

A

most values are δ15N = 0-10.. for all ages; ~2.4Ga very anomalous- δ15N values from 0-50

191
Q

why was δ15N so high 2.4Ga

A

the great oxidation– beginning of nitrification; before 2.4Ga there was no nitrate in the ocean

192
Q

N-fixation, δ15N vs TOC

A

δ15N = 0-(-2) –– Nitrogenase enzyme with Mo and Fe
δ15N = (-6) - (-8)––– nitogenase w/ V, or 2Fe
majority of values are in the 0-2 range.. modern style

193
Q

why Fe, Mo enzyme is ‘modern style’

A

Vnf, Anf, are less efficient and = higher fractionation (more -)

194
Q

Archaen nitrogenase enzyme

A

Fe-Fe, Fe was very soluble and abundant, Mo was insoluble due to anoxic waters

195
Q

geological N cycles

A

sedimentation

hydrothermal alteration

196
Q

N cycle, sedimentation

A

PN sink– deposited– nitrification/denitrification in sed.– converts to NH4+– substitutes into clay minerals

197
Q

NH4+ substitution into clay mineral

A

similar ionic radius as K+ (1.61-1.69 vs. 1.46-1.63 Å), can substitute for K+, especially in K; average concentration = 430±25ppm

198
Q

N cycle, hydrothermal alteration

A

new oceanic crust = low N (~1ppm)– hydrothermal alteration transfers N from O-rocks– increases concentration up to ~7ppm

199
Q

ocean crust

A

basalt and gabbro

200
Q

where to look for life

A

circumstellar habitable zone; not too cold, not too hot, just right

201
Q

boundaries on habitable zone

A

runaway greenhouse– hydrogen escape– ø —snowball earth– CO2 condenses

202
Q

early life, exploiting chemical gradients

A

chemolithoautotrophic– limited by gradients set up in natural environment

203
Q

after great oxidation, life using existing gradients

A

heterotrophic
photoautotrophic
shift in life– huge earth change– gave life unlimited energy supply

204
Q

evolution of human systems

A

hunter/gatherer––farming–– FF burning–– Nuclear––Solar
use of existing resource–– big resource change–– potential to have unlimited energy depending on our next steps; human system evolution somewhat parallels life system evolution

205
Q

remarkable stable time in Earths history

A

Holocene, last 10,000yrs

unprecedented within last few million years

206
Q

climate stability leads to

A

societal growth

207
Q

climate sensitivity

A

~3ºC, changes through time

208
Q

climate change scenarios

A

usually underestimate changes

209
Q

<450ppm CO2

A

ice on Antarctica

210
Q

> 450ppm CO2

A

no ice anywhere

211
Q

last ppm we will likely see a Holocene like climate

A

350

212
Q

how to deal with climate change

A

stop changing things or adapt

213
Q

land surface that is crop land

A

12%

214
Q

rivers that run dry before they reach the ocean, due to human extraction

A

25%

215
Q

sources of nitrogen fixation

A

marine: ~100 ?g/yr
terrestrial: ~100 ?g/yr
industrial Haber-Bosch: ~100 ?g/yr

216
Q

pre-industrial aragonite saturation

A

3.44

217
Q

carbonate ion concentration

A

16%

218
Q

effects of anthropogenic N use

A

eutrophication

219
Q

biggest international transfer of fixed nitrogen

A

food (shipping crops)

220
Q

Phosphorus use

A

extraction since pre-industrial has increased by a factor of 20

221
Q

N subduction zones

A

hot subduction zone- more N volatilized

cold subduction zone- more N survives past subduction barrier

222
Q

N that makes it past the subduction barrier

A

possibly sequestered into the mantle

223
Q

calculating N in the mantle

A

noble gasses
xenoliths and diamonds
experimental petrology

224
Q

N in atmosphere

A

4x10^18 kg N

225
Q

calculating mantle N w/ noble gasses

A

Ar, N2 similar behaviour in basaltic melt: measure N2/Ar ratio in basalt- estime N content of mantle

226
Q

MORB N2:Ar

A

~120

227
Q

OIB N2:Ar

A

~9300

228
Q

how to measure Ar/N2

A

calculate 40Ar in mantle, from?

proportion MORB, OIB source mantle: 80:120, use K concentration and decay rate, find total 40Ar in Earths history

229
Q

OIB

A

ocean island basalt

230
Q

BSE

A

bulk silicate earth

231
Q

K concentration

A

280±120ppm

0.0117% 40K

232
Q

40K decay

A

10.72%

233
Q

total 40Ar in Earths history

A

4.2±1.8x10^18 mol

234
Q

calculate N2 abundance

A

(4. 2±1.8x10^18mol - atmosphere 1.65x10^18mol - cont. crust 0.35x10^18) = 2.2±1.8x10^18mol
2. 2±1.8 x 120 and 9300 = N2 abundance

235
Q

N2 abundance

A

24±16x10^18 kg N

236
Q

calculating mantle N with xenoliths

A

find total N = 7x10^18kg in upper mantle; 3X smaller than N2/Ar estimate

237
Q

N is more compatible

A

under reducing conditions- low oxygen activity, lots of eletrons

238
Q

upper mantle minerals

A

olivine, pyroxene

239
Q

upper mantle minerals sequester how much N

A

20 atmospheric masses, mostly in the lowermost upper mantle

240
Q

TZ

A

transition zone: 410-660km depth

241
Q

LM

A

lower mantle: ≤660km to core-mantle boundary

242
Q

N in TZ and LM

A

TZ, LM reduced–– contain metallic Fe, N loves Fe, can dissolve NH4, or bond and make FeN nitrides; potential to hold 3X more than atmos.

243
Q

N2, 40Ar correlation indicates

A
  • mantle N recycled
  • mantle N came from surface
  • N movement through BSE directly influenced evolution of atmosphere
  • possible solution to FYSP
244
Q

solution to FYSP?

A

more N2 in atmosphere makes CO2 a more efficient GHG

245
Q

core N

A

lots of Fe, N very soluble in Fe

estimate of amount: 180-300x10^18kg

246
Q

core mass

A

1.83x10^24kg

247
Q

cornerstone of climate science

A

Milankovitch hypothesis

248
Q

variations in atmospheric CO2

A

lag change of global ice volume- insolation variations have a bigger impact than CO2 on ice volume

249
Q

suggested Milankovitch hypothesis

A

orbitally-induced variations in summertime insolation in the norther high latitudes are in antipodes with the time rate of change of ice sheet volume

250
Q

direct physical connection to insolation variations

A

rate of change of ice volume dV/dt

251
Q

importance of ice sheet parameters

A

volume: matters most for sea level change; ice sheet extent: matters most for albedo; ice sheet hight: matters most for atmospheric circulation

252
Q

A physical basis for life detection experiments

A

Lovelock, 1965; experiment in ET life should include- definition of life in terms favourable for recognition, description of past and present environment of planet to be sampled

253
Q

physical basis of life

A

life is one member of the class of phenomena which are open or continuous reaction systems able to decrease their entropy at the expense of substances or energy taken in from the environment and subsequently rejected in a degraded form

254
Q

broadness of physical basis of life

A

includes flames, vortex motion and others

255
Q

wherever life exists, its biochemical form will be

A

strongly determined by the initiating event, environment at time of initiation

256
Q

planet with life can be distinguished by

A

having orderliness, structures/events improbably in terms of thermodynamic equilibrium, extreme departures from an organic steady-state equilibrium of chemical potential

257
Q

experiments for detection of life

A

search for order

search for non-equilibrium

258
Q

search for order

A

gas chromatograph– mass speck seek ordered molecular sequences, chemical identities; seek ordered molecular weight distributions- biological polymers have sharply defined molecular weights (inorganics do not); listen for ordered sequences of sound

259
Q

search for non-equilibrium

A

differential thermal analysis (DTA) to find chemical disequilibrium by comparing planet atmosphere with inert gas, likely to see a reaction if planet is in equilibrium; search for compounds that are incompatible in the long-term; apparatus to recognize objects in non-random motion

260
Q

life ‘as we know it’ on mars?

A

-dry, -atmosphere thin, -no trace of O2, -less filtered insolation, -lots of UV, -possible large amount of nitrogen oxides

261
Q

A search for life on Earth from the Galileo spacecraft

A

Sagan et al., 1993; look for indication of life on Earth; indications of life- abundant gaseous O2, atmospheric CH4 in disequilibrium, radio transmission (intelligence)

262
Q

Implies oceans are composed of liquid water

A

high humidities over most of planet

263
Q

why water is an ideal medium for life

A

dielectric constant, solvation properties, heat capacity, temperature range or liquid state

264
Q

CH4 on Earth

A

CH4 oxidizes quickly, major discrepancy btw observation and thermodynamic equilibrium, ~1ppm, some mechanism is pumping CH4 into atmosphere, strong indication of life

265
Q

N2O on Earth

A

atmospheric life = ~50yrs, non-biological mechanisms are too minuscule to contribute as much as is seen

266
Q

unusual RED spectral imaging

A

corresponds to no plausible mineral- signature of light-harvesting pigment in a photosynthetic system (chlorophyll a,b)

267
Q

radio waves

A

asymmetry- detected on night-side (can escape ionosphere), constant frequencies suggest artificial origin, pulse-like amplitude modulation- artificial, never observed for natural radio emissions

268
Q

Bistability of atmospheric oxygen and the great oxidation

A

Goldblatt, 2006; history of earth = major transitions separated by long periods of relative stability

269
Q

earths largest chemical transition

A

the Great Oxidation, ~2.4ba; [O2] rose from 0.01PAL

270
Q

origin of oxygenic photosynthesis gave rise to

A

2 simultaneously stable steady states for atmospheric oxygen; low oxygen steady state persisted 300million years after onset of oxygenic photosyn.

271
Q

Great Oxidation =

A

switch to high oxygen steady state

272
Q

bistability from

A

UV shielding of troposphere by O3– nonlinear increase in lifetime of atmospheric O2

273
Q

O2 before life

A

<10^-12 PAL

274
Q

GO consequence of

A

oxygenic photsyn. occurred 300Myr prior; increased mantle outgassing, contradicts geological constraints; oxidation of crust- decreased metamorphic reductants ‘r’, increased primary productivity ‘N’

275
Q

major metabolic pathway before GO

A

CO2 + H2O + hv––– 1/2CH4 + 1/2CO2 + O2

276
Q

bistability feedback

A

O2 >2x10^-5PAL–– O3 forms–– decreased CH4 oxidation (reduced O2 sink)–– O2 levels increase–– further O3 formation

277
Q

MIF

A

mass independent fractionation

EOS (7 decks)

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