12-1 Sci
Layers of the Atmosphere
Unit.12-1
Learning Objectives
Identify the four main layers of the atmosphere.
Explain the characteristics of the atmosphere’s layers.
What is the atmosphere?
What gases are found in Earth’s
atmosphere?
How Is the Air Up There?
What changed as you increased in
altitude?
Four Main Layers of the Atmosphere
Troposphere
Stratosphere
Mesosphere
Thermosphere
Scientists divide Earth’s atmosphere
into four main layers according to
changes in temperature.
These layers are the troposphere,
the stratosphere,
the mesosphere,
and the thermosphere.
Start Taking Notes
Draw Two Columns (Atmosphere
Layer & Characteristics) & four
rows ( Names of the Layers)
The Troposphere
The troposphere
is where Earth’s
weather occurs.
Troposphere
lowest, layer of Earth’s atmosphere.
Tropo- means “turning” or “changing
The troposphere is the layer of the atmosphere in
which Earth’s weather occurs.
is the troposphere the densest layer of the
atmosphere
the troposphere is about 12 kilometers thick.
However, it varies from 16 kilometers thick above
the equator to less than 9 kilometers thick above
the North and South Poles.
The Stratosphere
The stratosphere contains the
ozone layer.
Stratosphere
the stratosphere extends from the top of the
troposphere to about 50 kilometers above
Earth’s surface.
Strato means “layer” or “spread out.”
the stratosphere is the second layer of the
atmosphere and contains the ozone layer.
The stratosphere is at a higher altitude than the
troposphere.
the lower stratosphere is cold, about –60°C.
, the upper stratosphere is warmer than the lower
stratosphere.
This is because the middle portion of the stratosphere
has a layer of air where there is much more ozone than in
the rest of the atmosphere
Ozone is a form of oxygen that has three atoms in each
molecule instead of the usual two.
When ozone absorbs energy from the sun, the energy is
converted into heat, warming the air.
The ozone layer protects living things from ultraviolet
radiation from the sun.
The Mesosphere
The mesosphere is the layer that
protects Earth’s surface from being
hit by most meteoroids.
above the stratosphere, a drop in
temperature marks the beginning of the
next layer, the mesosphere.
Meso- means “middle,” so the mesosphere
is the middle layer of the atmosphere.
The mesosphere begins 50 kilometers
above Earth’s surface and ends at an
altitude of 80 kilometers.
In the upper mesosphere, temperatures
approach –90°C.
the mesosphere is the layer of the
atmosphere that protects Earth’s surface
from being hit by most meteoroids.
Meteoroids are chunks of stone and metal
from space. What you see as a shooting
star, or meteor, is the trail of hot, glowing
gases the meteoroid leaves behind in the
mesosphere as it burns up.
The Thermosphere
The thermosphere is the outermost
layer of Earth’s atmosphere.
the thermosphere extends from 80
kilometers above Earth’s surface outward
into space. It has no definite outer limit.
Sunlight strikes the thermosphere first,
making the air very hot, up to 1,800°C.
The Two Layers of the Thermosphere
The thermosphere is divided into two
layers:
the upper layer, the exosphere
the lower layer, the ionosphere
the thermosphere has two layers. The
lower layer, the ionosphere, begins
about 80 kilometers above Earth’s
surface and extends to about 400
kilometers. The exosphere is the
upper layer. It extends from about 400
kilometers outward for thousands of
kilometers
.
Changing Temperatures in the Atmosphere
How does temperature change with altitude in the
stratosphere?
Why does temperature increase with altitude in the
stratosphere?
What layer of the atmosphere has the lowest
temperature?
Why does the temperature go so high in the
thermosphere?
Layers of the Atmosphere Overview
Stratosphere