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Atmosphere

Atmosphere. THE Layers of gases that surround the Earth. Composition: . 78% Nitrogen 21% Oxygen 1% Other Gases. Lower atmosphere is a mixture of many gases called air Remains the same until about 80km altitude Above 80km air is extremely thin, almost a vacuum

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Atmosphere

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  1. Atmosphere THE Layers of gases that surround the Earth

  2. Composition: • 78% Nitrogen • 21% Oxygen • 1% Other Gases Lower atmosphere is a mixture of many gases called air Remains the same until about 80km altitude • Above 80km air is extremely thin, almost a vacuum 99% of the atmosphere’s weight is within 32km of the surface

  3. Changes in the Earth’s Atmosphere • When earth was formed volcanic eruptions released gases such as CO2 • called outgassing • produced a poisonous atmosphere • About 2.5 bya cells began photosynthesis • Photosynthesisproduces oxygen as a waste product • Over millions of years the atmosphere filled to it’s current levels of oxygen

  4. What else is in the atmosphere: Water Vapor, Ozone and Dust • Water vapor enters the air through evaporation and transpiration • Ozone - a molecule of oxygen that has 3 oxygen atoms (O3) • Forms when ultra violet (UV) rays act on oxygen in the upper atmosphere • Ozone absorbs 99% of harmful UV rays • Dust includes tiny grains of rock, dirt, pollen, soot, chemicals and bacteria

  5. Atmospheric Pressure: • The pressure exerted on a surface by the atmosphere • Decreases as altitude increases • Measured using a barometer Units of measure: Atmospheres Mm or inches of mercury Millibars 1 atmosphere = 760 mm Hg = 1000 mb

  6. Layers of the Atmosphere: • Troposphere • Stratosphere • Mesosphere • Thermosphere http://www.youtube.com/watch?v=FHtvDA0W34I

  7. Structure of the Atmosphere Divided into five layers based on temperature changes • Troposphere – 0 – 18 km • Closest to the earth • Weather occurs here • Boundary of the troposphere is the tropopause • Stratosphere – 18 - 50 km • Clear and dry • Contains the ozone layer • Very little water vapor

  8. Troposphere: • Temperature decreases as altitude increases because its heated by Earth’s surface

  9. Stratosphere: • As altitude increases temperature increases because UV rays absorbed by ozone

  10. Structure of the Atmosphere • Mesosphere – 50-80 km • Gets colder with increasing altitude • Coldest temp in atmosphere in this layer (-80°C) • Thermosphere — 80-480 km • Very hot (980°C) • *The Ionosphere – • in the lower thermosphere and upper mesosphere • where electrically charged ions are formed • These ions reflect radio signals back to earth

  11. Aurora Borealis http://www.youtube.com/watch?v=MfPXLfkmQss

  12. Mesosphere: • Temperature decreases as altitude increases

  13. Thermosphere: • As altitude increases temperature increases because oxygen and nitrogen atoms absorb solar radiation

  14. Exosphere – above 500km • Outermost layer of atmosphere • Very few gas particles • No clear boundary between exosphere and space • Very low temperature

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