2 Characteristics All gases that surround the Earth, called air Altitude extends to ~80 km above the surfaceMost abundant elements:nitrogen, oxygen, argonMost abundant compounds:Carbon dioxide (CO2), water vapor (H2O)Characteristics
3 Nitrogen Cycle - moves nitrogen from the air, to soil, to plants and animals, and back to air. Nitrogen is removed from the air by nitrogen-fixing bacteria that live in the soil and on plant rootsWhy all that Nitrogen?
4 Ozone A molecule with 3 oxygen atoms Absorbs harmful UV radiation from the sunChlorofluorocarbons, or CFC’s, break down ozoneOzone
5 Layers of the Atmosphere Troposphere – where most weather occurs; most H20 and CO2 is hereStratosphere – includes the ozone layerMesosphere – where meteorites burn upThermosphere - high energy rays from the sun are absorbed by N2 and O2 here; hottest layerExosphere - Molecules from atmosphere escape into space; satellites orbit here.Layers of the Atmosphere
7 The gases in Earth’s atmosphere slow the escape of energy that radiates from Earth’s surface. Gases: carbon dioxide, methane, water vapor, nitrous oxide, fluorocarbonsSome heat escapes into spaceGreenhouse gases trap some heatSunlightEarth’s SurfaceAtmosphereThe Greenhouse Effect