earth’s early atmosphere
DESCRIPTION
Earth’s Early Atmosphere. First Atmosphere. Probably H 2 or He Rare on our planet, lost to space because: Gravity not strong enough to hold lighter gases No magnetosphere (Van Allen belt) to deflect solar winds Once we had a differentiated core, the heavier gases could be retained. - PowerPoint PPT PresentationTRANSCRIPT
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Earth’s Early Atmosphere
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First Atmosphere
• Probably H2 or He– Rare on our planet, lost to space because:• Gravity not strong enough to hold lighter gases• No magnetosphere (Van Allen belt) to deflect solar
winds
• Once we had a differentiated core, the heavier gases could be retained.
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Side note: Some of those solar particles hit our upper atmosphere
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Developing Atmosphere• Produced by volcanoes• Probably H2O, CO2, SO2, CO, S2,
Cl2, N2, H2, NH3, and CH4
• As Earth cooled...
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Here comes the Oxygen!
• Produced in two ways:– Photochemical dissociation
• Sun breaks up water with UV rays• 1-2% of Oxygen made this way• Now Ozone (O3) can form! (we’ll get to this in a second)
– Photosynthesis• CO2 + H2O + sun organic compounds + OXYGEN produced by
cyanobacteria and higher plants
• Evidence of this is shown in the rock history. There is less and less Oxygen in rocks as you go back in time.
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New evidence, as of November 2011 suggests that:
Early Earth did NOT start out with a heavy methane and CO2 atmosphere, but had a healthy dose of O2, very much like our current atmosphere.
THIS IS NOT WHAT IS ON THE TEST, HOWEVER!!!
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What is Ozone?
• Diatomic Oxygen is TWO atoms of oxygen bonded together to form oxygen gas.
• Ozone is THREE oxygenatoms bonded together.
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What does Ozone Do?
• It absorbs most of the harmful UV rays that enter out atmosphere.
• Up high in the atmosphere, it is beneficial.• At ground level, it is a pollutant and is harmful
to our health.• Ever smell that metallic tang near electrical
motors?
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So, now that we have some Oxygen…. Where does this Ozone come from?
First, we have to look at how our atmosphere is structured…..
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The ozone layer is found in the Stratosphere
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Formation of Ozone by UV rays
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The Truth
• Science is still not decided on the Ozone layer being destroyed by CFCs
• The Montreal Treat (to ban CFCs) was decided on without concrete data… only ideas, very political.
• Much of the studies and data used to “prove” the ozone depletion are faulty or politically driven.
• A 10% decrease in ozone would be the equivalent of moving 60 miles closer to the equator.– Moving from New York to Florida raises your UV exposure
by 200%.
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What you need to know for the Test
• The hole in the ozone layer threatens life because of raised UV penetration.
• It is caused by CFCs, Chlorofluorocarbons.• We must use less CFCs in aerosols, refrigerants
(AC liquids), use less foam insulation with CFCs, no halon fire extinguishers, or cleaners with CFCs.
• One Chlorine or bromine atom can destroy 100,000 ozone molecules during its life.