Transcript The Atmosphere

The Atmosphere
Chapter 26 page 641
First atmosphere
The first atmosphere was probably H
and He
 This was when the sun was still a
protostar
 When it became a star the initial blast
probably blew away the atmosphere

Composition of
atmosphere
Different now than early
earth. Why?
 Early atmosphere
came from out
gassing of volcanoes.
 Early earth CO2 and
water vapor.

Remember it was a very
hot place.

After condensation of water vapor
produced the earth's oceans, they swept
out the carbon dioxide and locked it up
into rocks, our atmosphere was mostly
nitrogen.
To get our present atmosphere
we needed oxygen.

How do we get it?

Plants: Stromatolites and algae at first
Photosynthesis
 H20 + CO2 + light

C6H12O6 + O2
With the production of oxygen, O2, we
could have ozone (O3).

Filters out UV light
Composition of
Atmosphere
KNOW 1st 2
 Nitrogen 78%
Oxygen
21%




Argon
Neon, helium,
hydrogen, methane
H2O vapor
CO2
Structure of the
Atmosphere

The
atmosphere
is divided
into five
layers. It is
thickest near
the surface
and thins out
with height
until it
eventually
merges with
space.
troposphere-
ground to 16km
The troposphere is
the first layer above
the surface and
contains half of the
earth's atmosphere.
 Weather occurs in
this layer.
 Warmest near ground,
cools as you go up

Stratosphere 16km-50km
UV absorbed by ozone in the
stratosphere
 -50 at bottom to 0C at top
 Many jet aircraft fly in the
stratosphere because it is very
stable

Mesosphere 50-80km
gases absorb little E
 0C at bottom to -90C at top
 Meteors burn up in the
mesosphere.

Thermosphere
Very little air but,
reaches 2000C--hot
 The thermosphere
is a layer with
auroras, meteors
and where the
space shuttle orbits

Ionosphere


Layer within the
thermosphere and
upper mesosphere
Ion rich charged
particles
Atmospheric O2 and N2
are stripped of electrons
by solar radiation


reflects radio signals
Aurora borealis-northern
lights
Exosphere

The atmosphere
merges into space
in the extremely
thin exosphere.
This is the upper
limit of our
atmosphere.
After this there are
radiation belts and magnetic fields of
interplanetary space
Magnetic field
Protects us from
the solar wind
 Remember the
effects shown in
The Core

Temperatures

This image shows the
average temperature
profile through the
Earth's atmosphere.
Temperatures in the
thermosphere are
very sensitive to solar
activity and can vary
from 500°C to
1500°C.
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The source of this material is Windows
to the Universe, at
http://www.windows.ucar.edu/ at the
University Corporation for Atmospheric
Research (UCAR). ©1995-1999, 2000
The Regents of the University of
Michigan; ©2000-02 University
Corporation for Atmospheric Research.
All Rights Reserved.