EARTH

EARTH

1. Atmosphere: made up of gas, begins at earth surface and leads up into exosphere.

   • 78% N2
   • 21% O2
     • LAYERS OF THE ATMOSPHERE
       • Thermosphere
         • Outermost layer. 84.9km and higher.
         • Temp. increase with height
         • Ionosphere
           • Extends from meso-thermosphere
           • Contains ions and free electrons
       • Mesosphere
         • 47km to 84.9 km
         • Temp. decrease with height
       • Stratosphere
         • Contains the ozone layer (O3 molecules). Upper boundary: stratopause
         • 11km to 47km
         • Temp. increase with height
       • Troposphere
         • 0-11km
         • Temp. decrease with height
         • Almost all clouds and weather occur in this layer. Upper boundary: Tropopause
   • HYDROGEN CYCLE
   • 0.9% argon
   • Current:
   • Past: composed of hydrogen and helium
     • Escaped to space as temperatures were too high, new gases resulted from 'outgassing'
       • Outgassing: release of gas from the earth's interior
       • Condensation of water vapour as water cooled down formed lakes and oceans
         • Lakes and oceans absorbed CO2 from atmosphere (can be defined as a sink)
       • When O2 producing plants evolved they formed modern atmosphere

2. Lithosphere: earth surface- specific to land

3. Hydrosphere: bodies of liquid water (not ice)

4. Biosphere: all living organisms on earth.