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68 Cards in this Set
- Front
- Back
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___ signals the potential for life, but only ___ is a sign of it's fulfullment because the latter is produced only by life
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H2O signals the potential for life, but only O2 is a sign of it's fulfullment because the latter is produced only by life
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__ is the reactive constituent of air
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O2
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combustion and ________ are essentailly the same. Why?
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human respiration
they both consume O2 and hydrocarbons to produce CO2 and H2O |
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O2 is not only essential for life, but it is also _____ depending on concentration and duration of exposure. why is it so?
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toxic
causes massive generation of free radicals in the brain |
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what is the free radical theory
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aging (and death) is caused by breathing O2 over a lifetime because cells are damaged by free radicals
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What is a reducing atmosphere?
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similar to Jupiter's; no O2 but has H2, NH3, CH4 + CO2, H2O, N2, H2S
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What was the Miller-Urey experiment?
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they passed lightning through a combination of gases similar to early earth and a brown solution with organic compounds and amino acids was formed
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One theory of where life formed involves hydrothermal vents. What kind of energy source would early life forms have used?
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they would have oxidized sulfur compounds
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single-celled life in oceans superseded by first photosynthetic bacteria ....
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the cyanobacteria
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why did oxygen build up in the ocean before being released into the atmosphere?
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O2 reacted with minerals like Fe2+, which acted as a buffer
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what are the 2 theories of snowball earth (when tropics were covered in glaciers 1km thick)
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1. O2 used up CH4 (which is a greenhouse gas ... etc.)
2. tectonic activity exposed the earth, carbonic acid reacted with rocks, PS occurred, CO2 left atmosphere (CO2 is a greenhouse gas ... etc.) |
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how did snowball earth end? did it only happen once?
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ice-covered planet has no PS and no erosion -> volcanic eruptions caused CO2 to build up (greenhouse gas ... etc)
warming, snowballing, and melting event occurred several times as part of a feedback loop |
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how did life survive snowball earth?
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tough cyanobacteria could survive freezing and then bloom in melting thanks to nutrients from glaciers
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rise of O2 in atmosphere (0.58bya) followed by ______ _______ (0.55bya) when macroscopic fossils of large animals first appear
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Cambrian explosion!
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rising O2 levels opened new horizons for precambrian life: the cambrian explosion caused by interplay between _____ possibility and ______ opportunity
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interplay between genetic possibility and environmental opportunity
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___ is called "earth's natural sunscreen" ... why?
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O3, reduces UV penetration by 70%!
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what organism indirectly caused the formation of the ozone layer?
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cyanobacteria -> O2 -> (cambrian explosion) -> ozone layer!
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What does the coevolution of macro- and microscopic events on earth refer to?
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macro = atmospheric composition
micro = cyanobacteria / life |
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sum up the Gaia hypothesis as we learned it
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if life hadn't evolved when it did, the atmosphere would not have the necessary composition to support life, but since life did evolve the atmosphere is able to sustain life
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how do we know the historical CO2 concentrations 200,000 years ago and before that?
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now - 200,000 years ago = ice core data
before that = gas trapped in amber |
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define steady state
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inputs = outputs/sinks
value does not change much over time |
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What is a great proxy for historical temperature?
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deuterium in arctic ice
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what are the layers of the atmosphere from highest to lowest (low=ground)?
what is even above the highest level? |
TMST
thermosphere, mesosphere, stratosphere, and troposphere ionosphere |
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why is the tropopause a barrier for H2O vapour?
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because above it, in the stratosphere, the temp is like -65
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what happens when free electrons are recaptured by ionized gases?
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aurora borealis
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how are absolute and relative concentrations of atmospheric gases measured in?
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absolute: partial pressure (molecules per cm3)
relative: ppm |
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what are the 3 important ranges of the electromagnetic spectrum
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ultraviolet (50-400nm) - highest energy
visible (400-750) infrared (750+) |
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what is a photochemical reaction?
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a chemical reaction initiated by light
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what happens to O2 radicals high up in the atmosphere?
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since O2 is sparse the radicals recombine with one another to reform molecular O2
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the lifetime of ozone at __km is what? what is its relative concentration?
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1/2 hour at 30km
10 ppm |
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what is the Chapman mechanism? where does it occur?
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O2 -> O + O
O + O2 -> O3 + heat O3 -> O2 + O (starts over) |
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how does the atmosphere prevent harmful solar UV radiation from reaching the earth's surface?
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radiation breaks the bonds of molecules in the atmosphere
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a diatomic molecule has what 3 kinds of energy?
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vibrational, translational, and rotational
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why don't N2 and O2 absorb IR (recall they can absorb UV)?
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because their center of mass = center of charge so they don't have a dipole moment and so cannot interact with IR light
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what character of a molecule increases its capacity absorb IR?
an example |
the number vibrational modes
CH4 has 6 vibrational modes and is the most (?) efficient at absorbing IR |
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define albedo
what is earth's albedo approx. |
ratio of reflected to incoming solar radiation
0.3 |
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what affect does algal bloom have on albedo?
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increases
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what is sensible vs. latent heat
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sensible can be felt
latent = evaporation/melting increases H2O in air = warming |
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what two things add up to account for heat transfer to poles?
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50% atmospheric transport
50% by oceans |
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what 2 things force the ocean conveyer belt to keep moving? i.e. what forces the water downwards around Greenland?
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thermal forcing - heat is released
haline forcing - water is more saline/dense |
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what happen to the ocean conveyor belt if Greenland melts? then what?
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water is cooled AND diluted so it doesn't sink down in the critical part - belt shuts down -> no warm water would come north -> next ice age
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El Nino _____ affects Peru's growing season. El Nina are becoming more ____ and ______.
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El Nino positively affects Peru's growing season. El Nina are becoming more frequent and severe.
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in order for IR radiation to be absorbed by a molecule, the molecule must have either a ________ or a __________. Give an example of each.
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induced dipole moment - CO2
permanent dipole moment - H2O |
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4 molecule that absorb IR
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CO2
H2O CH4 O3 |
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what makes a gas a greenhouse gas (3)?
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1. must absorb IR
2. must be long-lived 3. must be in high enough concentration to affect the global radiation budget |
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What does this define: the redirection of thermal IR towards earth.
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greenhouse effect
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how far above ground in the tropopause?
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10 km
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what is radiative forcing?
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change in average net radiation at the tropopause due to either a change in incoming solar or outgoing IR radiation
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what do + and - radiative forcing values indicate?
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+ net warming
- net cooling |
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do aerosols cause net warming or cooling? how are they different from greenhouse gases?
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depends! can cause cooling (may even outweigh effects of greenhouse gases)
aerosols DO NOT accumulate in the atmosphere |
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how does stratospheric ozone affect radiative forcing?
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negative (cooling) because it's above the tropopause and so reflects incoming solar radiation
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What is mechanism I of stratospheric O3 destruction?
What is one example of X? What does this mechanism require? |
X + O3 -> XO + O2
XO + O -> X + O2 (X = free radical catalyst = can do this over and over!) X = NO (comes from N2O + O) Requires stratosphere O radicals |
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What is mechanism II of stratospheric O2 destruction?
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X + O3 - > XO + O2 (same as mech I)
X + O3 - > XO + O2 - again now XO + XO -> [XOOX] -> X + X + O2 |
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how is O3 self-healing?
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if rate of O3 destruction increases (more X) there can be a lower concentration, but the Chapman mechanism will keep going so O3 cannot be permanently and totally destroyed
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which mechanism of stratospheric 3 destruction happens when [X] are high / no O radicals?
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II
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one Cl radical can destroy ~10,000 O3! but ...
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99% of Cl is catalytically inactive
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why are CFCs dangerous to ozone?
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they are a precursor to a catalyst (X)!
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How are polar stratospheric clouds important?
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they convert all inactive forms of Cl into Cl and ClO radicals! (Cl2 + light)
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which mechanism destroys the most O3 in the antarctic? Why>
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II
low temps stabilize the dimer (XOOX), which drives the chemistry |
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what is photochemical smog?
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high levels of O3 in urban areas because of light-induced chemical reactions
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what are the primary and secondary gaseous air pollutants?
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primary = VOC's and NO
secondary = O3 and HNO3 primary + sun -> secondary |
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3 conditions for bad smog?
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1. traffic/people (NO, HC)
2. sun 3. little air movement |
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4 ingredients of smog
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O2 + NO + HCs + sun
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2 types of tropospheric pollutants
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gases
particulate matter |
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NOx and SO2 have both ______ in recent year. why?
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decreased because of controls
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main cause of acid rain
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SO2
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great way to reduce NOx
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catalytic converters
2NO -> N2 + O2 |
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what is the GWP
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global warming potential
how effective a greenhouse gas is relative to CO2 |
