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Chapter 3
Section 2: The Atmosphere
The Atmosphere

Mixture of gases
that surround the
earth.
Composition of the
Atmosphere
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78% nitrogen
21% Oxygen
1 % other (argon, carbon dioxide,
methane, and water vapor)
SOLIDS: soil, salt, ash from fire,
volcanic ash, particulate matter from
skin, hair, bits of clothing, pollen,
bacteria, viruses
Air Pressure
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Gravity pulls the
Earth’s atmosphere
towards earth
Atmosphere is
denser near Earth’s
surface.
Layers of the Atmosphere

Four layers:
–
–
–
–
TROPOSPHERE
STRATOSPHERE
MESOSPHERE
THERMOSPHERE
Troposphere
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Nearest Earth’s surface
Extends to 18 km (11mi) above Earth’s surface
Densest layer
Temperature decreases as altitude increases.
Stratosphere
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Extends from 18km to 50 km (31 mi).
Temperatures rise as altitude increases.
Ozone absorbs UV energy and warms air.
Mesosphere
Extends from 50 km to 80 km (49mi).
 Coldest layer
 As low as
-93 degrees C.

Thermosphere
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Farthest from earth.
Nitrogen and oxygen
absorb solar
radiation.
Temperatures above
2,000 degrees C.
Lower region of
thermosphere
absorbs x-rays and
gamma rays causing
energy to be radiated
as light (Northern
lights)
Energy in the Atmosphere

Sun’s energy is transferred in 3 ways:
–Radiation: transfer of heat
across space in the atmosphere.
–Conduction: flow of heat from
warmer object to colder one.
–Convection: transfer of heat
by air currents.
Heating of the
Atmosphere

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
Solar energy reaches earth as
ELECTROMAGNETIC RADIATION
(visible light, infrared radiation,
ultraviolet light)
Small amount of radiation penetrates,
but a large amount of energy reaches
earth.
Excess heat is radiated back into the
atmosphere.
The Movement of Energy
in the Atmosphere


Air moves upward, downward and
sideways causing earth’s weather.
Warm air rises into the atmosphere,
cools, and sinks back down toward
earth. The process repeats causing a
CONVECTION CURRENT.
The Greenhouse Effect


Gases trap heat near the earth and
keep earth warm.
Greenhouse gases: water vapor,
Carbon dioxide, methane, nitrous
oxide.
Objectives

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Describe the composition of the
Earth’s atmosphere
Describe the layers of the Earth’s
atmosphere.
Explain the three mechanism’s of heat
transfer in Earth’s atmosphere.
Explain the greenhouse effect.
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atmosphere.swf