Download Chapter 12 Atmosphere

EARTH’S
PROTECTIVE BUBBLE
NASA accessed via Wikipedia
LOOKING AT
THE EARTH’S
ATMOSPHERE
Earth’s Atmosphere
• compared to the size of
the Earth (104 km), the
atmosphere is a thin
shell (120 km).
http://www.gsfc.nasa.gov/gsfc/earth/pinatuboimages.htm
WHAT’S SO SPECIAL?
 Earth is surrounded by a blanket of air called the atmosphere
 Extends near or over 600 kilometers from Earth’s surface
 Held by Earth’s gravitational pull
 Composed of many different gases
 Separated into several different layers
 Protects us from outer space
 Blocks out dangerous rays (UV) from the sun
 Quite transparent to visible light
Ionosphere
Heterosphere
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Homosphere
A PROFILE OF THE
ATMOSPHERE
REVEALS IT CAN
BE DIVIDED INTO
DISTINCT LAYERS
EACH LAYER CAN
BE DEFINED BY
THE GASES THAT
COMPRISES IT OR
TEMPERATURE
VARIATION OR
ELECTRICAL
PROPERTIES
SEPARATING THE
LAYERS IS A
BOUNDARY OR
“PAUSE” WHERE
THE GREATEST
CHANGES
PROPERTIES
OCCUR
The source of this material is Windows to the Universe, at http://www.windows2universe.org http://www.windows.ucar.edu/ at the National Earth Science Teachers Association (NESTA) <http://www.ucar.edu>. Windows to the Universe® is a registered trademark. All Rights Reserved
ATMOSPHERIC GASES
(MIXTURE OF GASES, SOLIDS, AND
LIQUIDS)
Nitrogen ~78%
Oxygen ~20%
Argon ~ 1%
Trace Gases of neon, helium, methane, krypton,
xenon, hydrogen, ozone and
Carbon Dioxide ~.04% (and rising)
 Keeps Earth warm and is used by plants to make food
 Particles are also in the air
Origin of Modern Atmosphere
• original atmosphere surrounded the homogenous planet
Earth and probably was composed of H and He
• second atmosphere evolved from gases from molten
Earth
– H2O, CO2, SO2, CO, S2, Cl2, N2, H2, NH3, and CH4
– allowed formation of oceans and earliest life
• modern Atmosphere
– evolved after Cyanobacteria started photosynthesizing
– oxygen produced did not reach modern levels until about 400
million years ago
www.degginger.com/digitalpage.html
Air Pressure
Air Column
The weight of the column of air
above you puts pressure on you.
How does pressure from air
molecules keep you from being
crushed?
Air Pressure
Reading a Mercury Barometer
What would a low air pressure reading look like?
Air Pressure
Inside an Aneroid Barometer
An aneroid barometer has an
airtight metal chamber, shown
in red. Which diagram shows
the aneroid barometer under
high pressure and which shows
it under low pressure?
Units of Pressure
• One atmosphere = 101.3 kPa
• Pressure is also measured in inches of
mercury (inHg)
• One atmosphere = 29.9 inches of
mercury
Air Pressure
Effect of Altitude on Pressure and Density
How densely packed would the molecules be at the different altitudes?
Atmospheric Temperatures
Differences in temperature are what
separate each layer in the atmosphere
from the one above and/or below it.
Atmospheric Temperatures
In the troposphere:
•
As altitude increases,
temperature decreases
Altitude
Temperature
Atmospheric Temperatures
In the stratosphere:
•
The stratosphere is cold
except in its upper
region where ozone is
located.
Altitude
Temperature
Ozone
Layer
Atmospheric Temperatures
In the Mesosphere:
•
This is the COLDEST
layer in the atmosphere.
Altitude
Temperature
Atmospheric Temperatures
In the thermosphere:
•
Even though the air is thin
in the thermosphere, it is
very HOT.
Altitude
Temperature
Atmospheric Temperatures
Beyond the thermosphere is
the exosphere which
leads into outer space
where it is very cold,
because there is little to
no atmosphere to
absorb the Sun’s heat
energy.
Altitude
Temperature
Atmospheric Temperatures
Temperature
Outer Space
Exosphere
Thermosphere
Mesosphere
Stratosphere
Troposphere
Earth’s Surface
Altitude
Atmospheric Pressure
•
Air pressure is the
force exerted by the
gases pushing on an
object.
•
Air pressure is greatest
near the surface of the
Earth in the troposphere.
Altitude
Air Pressure