Section 11.1 – Atmosphere Basics
8th Grade Earth and Space Science
Class Notes
Atmosphere Basics
• Combination of gases, dust, water droplets,
and ice crystals
• Surrounds the Earth
• Extends from the Earth’s
surface to outer space
Picture of the Earth’s
atmosphere taken
from a space shuttle
Permanent Atmospheric Gases
• Earth’s atmosphere consists mainly of
nitrogen (78 percent) and oxygen (21
percent).
• The amounts of nitrogen and
oxygen in the atmosphere are
fairly constant over recent
time.
Variable Atmospheric Gases
• The concentrations of some atmospheric
gases are not as constant over time.
• The amount of water vapor, ozone, and
carbon dioxide vary significantly from place to
place.
Water Vapor (H2O(g))
• Invisible, gaseous form of water
• Can range of 0% - 4%
• Concentration depends on the seasons,
altitude, and properties of the surface
underneath
Carbon Dioxide (CO2)
• During the past 150 years, the concentration
of atmospheric carbon dioxide has increased,
due primarily to the burning of fossil fuels.
• Currently 0.039% (up by 0.028%)
Ozone (O3)
• Mostly in ozone layer (20 – 50 km above)
• Only 0.0012% but plays important role in
blocking out harmful rays from the sun
• Concentration has decreased due to CFCs
which are now banned
• Scientists estimate it should
fully recover by the 2100
Atmosphere Particles
• Contains variable amounts of solids in the
form of tiny particles, such as dust, salt, and
ice
• Fungi and bacteria are often attached to these
particles
Fluorescent sample
of bacteria taken
from the air.
Atmospheric Layers
Troposphere
•
•
•
•
•
Closest to the Earth’s surface
Contains most of the atmosphere’s mass
Weather occurs in this layer
Air temperature decreases with altitude
Top is called tropopause
Stratosphere
• Above tropopause
• Contains the ozone layer
• Air temperature increases with altitude since
the ozone layer absorbs the sun’s energy
• Ends at the stratopause
Mesosphere
• Above the stratopause
• Air temperature decreases with altitude since
very little solar radiation is absorbed
• Ends at mesopause
Thermosphere
• Low air density so temperature rises (can be
over 1000°C)
• Contains the ionosphere (made up of charged
particles)
• Ends at thermopause
Exosphere
• Outermost layer
• Transitional region between the Earth’s
atmosphere and outer space
Review of Thermal Energy and Heat
• Remember – all matter is made of particles in
constant, random motion!
• These moving particles contain kinetic energy.
• The total kinetic energy of the moving
particles is called thermal energy.
Less thermal
energy 
More thermal
 energy
Review of Thermal Energy and Heat
• Heat is the transfer of thermal energy from
regions of higher temperature to regions of
lower temperature
Direction of
movement 
Energy Transfer in the Atmosphere
• In the atmosphere thermal energy is
transferred by:
– Radiation
– Conduction
– Convection
Radiation
• Transfer of thermal energy by electromagnetic
waves
• Thermal energy is transferred from the Sun to
Earth by radiation
Absorption and Reflection
• Incoming solar radiation is either reflected
back into space or absorbed by Earth’s
atmosphere or its surface.
• 30% reflected
• 20% absorbed
by atmosphere
and clouds
• 50% absorbed
by Earth’s surface
Rate of Absorption
• Depends on physical characteristics of the
surface and the amount of solar radiation
• Examples – water heats and cools more
slowly; dark colors absorb energy faster
Solar Radiation Around
the World
Darker = more
Conduction
• Transfer of thermal energy when objects at
two different temperatures are in contact
• Occurs between the Earth’s surface and
lowest part of the atmosphere
Convection
• Remember – convection is the transfer of thermal
energy by the movement of heated material from
one place to another
• Near the Earth’s surface air becomes heated,
expands, and rises then as it rises it cools, contracts,
and sinks.
• This creates convection currents in the atmosphere.