earth’s atmosphere chapter 3, section 2 describe the composition of the earth’s atmosphere...
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Earth’s Atmosphere
Chapter 3, Section 2
•Describe the composition of the Earth’s atmosphere•Describe the layers of the Earth’s atmosphere•Explain 3 mechanisms of heat transfer in Earth’s atmosphere•Explain the greenhouse effect
General Description of Atmosphere
• Mixture of gases– Nitrogen– Oxygen– Carbon dioxide & others
• Addition/removal results in change– Living organisms (plants & animals)– Volcanic eruptions– Vehicles/industries
• Insulates Earth’s surface
Composition of Earth’s Atmosphere• Gases– 78% Nitrogen– 21% Oxygen– 1% other (Ar, CO2, CH4, H2O)
• Atmospheric Dust– Solid particles
• Soil, salt, ash fro fire & volcanic eruptions• Particulate matter (combustion, skin, hair,
clothing bits, pollen bacteria & viruses• Aerosols (tiny liquid droplets)
• Creates air pressure– Due to gravitational pull– Greatest near Earth’s surface
Earth’s Atmospheric Layers
(Ionosphere)
Earth’s Atmospheric Layers
• Divided into 4 layers based on– Temperature
changes– Pressure
changes
Location of Atmospheric Layers above Earth’s Surface
Troposphere• Nearest Earth’s surface (up to 18 km)• Makes up 75% of Earth’s atmospheric mass• Densest layer• Temperature & pressure decrease with altitude– Except tropopause – very top of layer– Stable temperature – called “cold trap”
• Wider at equator than poles• Location of weather occurrence– Uneven heating due to convection current & winds– Causes cloud formation (rising water vapor cooled)
• Related to Greenhouse effect
Stratosphere
• 2nd layer above Earth’s surface (32 km thick, 18-50 km above surface)
• Temperature increases with altitude
• Contains ozone layer– Reduces UV radiation– Thinning in Europe, Asia,
North America & Antarctica
Mesosphere
• 50-80 km above surface• Coldest layer– Temperature decreases
with increase in altitude– -30°C (-130°F)
• Slows, prevents meteors entering atmosphere
Thermosphere
• 80 – 1000 km above surface
• Very hot temperatures (200-2000°C or 360-3600°F)
• Ionization of gases – N2 & O2 absorb X-rays &
gamma rays– Radiate light (auroras)
• Reflect radio waves• Area where shuttles orbit
Energy Transfer in the Atmosphere• Radiation– Electromagnetic waves – absorbed & converted to
heat– Visible light, X-rays, UV, Gamma (from sun)
• Conduction– Transfer by contact between different matter
• Convection – Caused by temperature differences & changes in
densities of materials– Occurs only in fluids– Creates currents
Energy Transfer Diagram
Atmospheric Energy
• Reaches Earth as electromagnetic radiation– ½ entering atmosphere reaches surface– ½ absorbed or reflected by gases, clouds, dust
• Oceans & land radiate energy back into atmosphere– Prevents overheating of Earth’s surface
• Dark colors absorb more energy than lighter ones– More energy released by darker colors– Explains higher temperatures in cities than surrounding
country sides
Energy Movement in Atmosphere
• Result of convection currents– Air heated by Earth’s surface & rises into
atmosphere– Cools as it rises & becomes more dense & sinks– Continual process results in circular movement of
air (currents)– Occurs in troposphere, resulting in weather
occurrences (rain, wind, tornadoes, etc.)
Greenhouse Effect• Warming of Earth’s surface & lower atmosphere • Due to carbon dioxide, water vapor & other gases
(methane, nitrous oxide) absorbing & radiating infrared waves – Called “greenhouse gases”– Maintain temperatures that support life
• Excess amounts of carbon dioxide & methane result in increased heat retention– Caused by natural & industrial events– Cause abnormal increases in temperatures (heat) – Result in shifts in climatic zones, melting of polar ice
caps, increased ocean levels around the world
How is Earth’s atmosphere like glass in a car?
• Both allow solar energy to pass through
• Both can absorb and stop heat from escaping
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