The Atmosphere

The Atmosphere

1. the FIRST TWO BILLION YEARS

   • the surface of the Earth was originally molten, so super hot that any atmosphere just boiled away into space
     • after a few million years of boiling, the planetary metaphorical hot potato cooled down just enough to form a thin crust
       • nevertheless, volcanoes kept erupting and spewing out loads of gases, including carbon dioxide, water vapour and nitrogen
         • we think that this was how the atmosphere was formed - if this was the case, then the early atmosphere would've been mostly carbon dioxide and water vapour with hardly any oxygen
           • as the earthy potato continued cooling, water vapour condensed to form oceans

2. the NEXT TWO BILLION YEARS

   • green plants evolved over most of the Earth, quite content in the carbon dioxide-rich atmosphere
     • lots of the early carbon dioxide got dissolved into the ocean and those happy green plants removed a whole load more through photosynthesis, while simultaneously producing oxygen
       • when plants died they were buried under layers of sediment and the carbon that they'd removed from the air (as carbon dioxide in photosynthesis) became locked up in sedimentary rocks as insoluble carbonates and fossil fuels
         • this build-up of oxygen in the atmosphere killed off some early organisms, who couldn't tolerate it, but allowed other more complex organisms to evolve and thrive

3. the FUTURE

   • HUMAN ACTIVITY is CHANGING the ATMOSPHERE(!)
     • the concentrations of nitrogen, oxygen and argon in the air are pretty much constant...
       • ...BUT human activity is adding small amounts of POLLUTANTS to the air
         • for example....
           • carbon dioxide
           • carbon monoxide
           • particulates (i.e. soot etc.)
           • nitrogen oxides
           • sulfur dioxide
         • these pollutants come from many different sources, exempli gratia...
           • burning fuels
             • in power stations
             • in vehicles
           • nature
             • gases (and particulates as well) released from volcanoes like in the first two billion years
         • some pollutants are DIRECTLY harmful to humans
           • this can cause disease (bad) or death (worse) to people who breathe enough in
           • उदाहरण के लिये...
             • carbon monoxide reduces the amount of oxygen that the blood can carry, causing flu-like symptoms and then death (notoriously difficult to treat)
         • other pollutants are INDIRECTLY harmful to humans, damaging our environment
           • για παράδειγμα...
             • sulfur dioxide can cause acid rain → pollutes rivers and lakes → kills fish → people get hungry
             • other pollutants (მაგალითად carbon dioxide) are causing climate change, which is big and scary and likes to eat people and so forth

4. ATMOSPHERE: "The envelope of gases surrounding the earth or another planet"

5. NOW

   • by now, pretty much all of the carbon dioxide has been absorbed by plants, and we have been left with the amounts of gases above...

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