The Atmosphere
Atmosphere: mixture of gases that surround a planet
Includes nitrogen, oxygen, carbon dioxide, & other gases
Gases can be added/removed by volcanic gases, automobiles, & living organisms
Ex: photosynthesis, cell respiration
The Atmosphere
The atmosphere insulates Earth’s surface
Slows the rate at which the Earth’ surface loses heat
Keeps a stable temperature
Composition of the Atmosphere
Nitrogen: 78%
Enters the atmosphere during volcanic eruptions & when plants/animals decay
Oxygen: 21%
Mostly produced by plants
Other gases: argon, carbon dioxide, methane, water vapor
Atmosphere contains many types of tiny, solid particles called atmospheric dust
Air Pressure
Atmosphere is denser near the Earth’s surface
Due to gravity
Makes breathing difficult at higher altitudes
Layers of the Atmosphere
Layers divided based on temperature changes
The Troposphere
The Stratosphere
The Mesosphere
The Thermosphere
The Troposphere
Lowest layer of the atmosphere
As altitude increases, temperature decreases
Where weather conditions exist
Densest atmospheric layer
Extends 18 km above the surface
The StratosphereAbove the troposphere
10-50 km above the surface
As altitude increases, temperature increases
Airplane level
Ozone (O3) absorbs sun’s ultraviolet (UV) energy, warming the air & reducing UV to reach Earth
UV can damage living cells
The Thermosphere
Farthest from the Earth’s surface
Nitrogen & Oxygen absorb solar radiation
Temperatures >2,000°C
Air is so thin that particles barely collide
Little heat is transferred
Would not feel hot to us
The Thermosphere (cont’d)
X-rays & gamma rays absorbed by nitrogen & oxygen causes electrically charged atoms (ions)
Ions radiate energy as light
Causes auroras (Northern & Southern Lights) near the poles
The Greenhouse Effect
Greenhouse Effect: warming of the Earth’s surface & lower atmosphere that occurs when gases absorb & reradiate infrared radiation
Makes temperature warm enough for life
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