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Layers of the Atmosphere
Study Jams Video: Earth’s Atmosphere
http://studyjams.scholastic.com/studyjams/jams/science/weather-andclimate/earths-atmosphere.htm
What Is Earth’s Atmosphere Made Of?
An atmosphere is a layer of gases that surrounds a
planet or moon. On Earth, the atmosphere is often called
just “the air.” When you take a breath of air, you are
breathing in atmosphere.
The air you breathe is made of many different things.
Almost 80% of it is nitrogen gas. The rest is mostly oxygen,
the gas we need to live. There is also water in the
atmosphere. Some of it is invisible, in the form of a gas
called water vapor.
Water is also found in the atmosphere as water
droplets and ice crystals, like those that make up clouds.
The atmosphere also contains tiny particles, or solid
pieces. These particles are things like dust and dirt from
continents, salt from oceans, and ash from volcanoes.
Where Do the Gases in the Atmosphere
Come From?
The gases in Earth’s atmosphere come from many different
sources. The table below shows some of those sources.
Why Does Air Pressure Change with Height?
Air pressure is how much the air above you weighs.
It is a measure of how hard air molecules push on a surface.
We don’t normally notice air pressure, because our
bodies are used to it.
As you move up from the ground and out toward
space, there are fewer gas molecules pressing down from
above. Therefore, the air pressure drops. The higher you
go, the lower the air pressure gets.
Using the passage above complete the questions below.
1. Define Atmosphere:
2. Why is the Earth’s atmosphere important?
3. What is air pressure?
4. What is the relationship between air pressure and altitude?
5. What causes air pressure?
6. Where is air pressure the greatest? Why?
Atmospheric Layers
Earth’s atmosphere is held in place by gravity. The atmosphere protects life on
the planet by absorbing ultraviolet radiation and by regulating temperature.
There is no exact place where Earth’s atmosphere ends. Instead, it just gets
gradually thinner and thinner (less dense) until it merges with outer space where
it consists mostly of interplanetary gases such as hydrogen and helium.
The atmosphere surrounds Earth and protects us by blocking out dangerous rays
from the sun. The atmosphere is a mixture of gases that becomes thinner until it
gradually reaches space. It is composed of Nitrogen (78%), Oxygen (21%), and
other gases (1%).
Oxygen is essential to life because it allows us to breathe. In addition, some of
the oxygen has changed over time forming ozone. The ozone layer filters out the
sun's harmful ultraviolet radiation. Recently, there have been many studies on
how humans caused a hole to develop in the ozone layer.
Humans are also affecting Earth's atmosphere through the greenhouse effect.
Due to increases in gases, such as carbon dioxide, that trap heat being radiated
from the Earth, scientists believe that the atmosphere may have problems
balancing the incoming solar radiation and the reradiated heat from Earth's
surface creating the greenhouse effect.
The atmosphere is divided into five layers depending on how temperature
changes with height. Most of the weather occurs in the first layer.
The troposphere is the atmospheric layer closest to the earth. It is often referred
to as the “lower atmosphere.” The troposphere is the lowest region of the Earth's
atmosphere, where masses of air are very well mixed together and the
temperature decreases with altitude.
The air is heated from the ground up
because the surface of the Earth absorbs energy and heats up faster than the
air. The heat is mixed through the troposphere because on average the
atmosphere in this layer is slightly unstable. Weather occurs in the Earth's
troposphere. In fact, most clouds form in this layer. As you move higher into the
troposphere (say, to the top of a mountain), air temperature decreases as the
altitude increases.
The stratosphere is just above the troposphere, starting at an average altitude
of about 7 miles above sea level. The air here is more dry and less dense. Only
the highest clouds can be found in this layer. Aircraft often fly in the lower
stratosphere to escape the turbulence present in the troposphere. Near the top of
the stratosphere lies the ozone layer. In the Earth's stratosphere, the
temperature increases with altitude (as opposed to the troposphere, where it gets
colder with altitude).The increasing temperature in the stratosphere is caused by
the presence of a layer of ozone near an altitude of 25 kilometers. The ozone
molecules absorb high-energy UV rays from the sun, which warm the
atmosphere at that level.
The mesosphere lies just above the stratosphere, ranging from about 30 to 50
miles above sea level. This layer contains chemicals which absorb energy from
the sun. Together, the stratosphere and the mesosphere are often called the
“middle atmosphere.” In the Earth's mesosphere, the air masses are relatively
mixed together and the temperature decreases while altitude increases.
Atmospheric temperatures reach the lowest average value of around -90°C in the
mesosphere. This is also the layer in which a lot of meteors burn up while
entering the Earth's atmosphere. This layer is the coldest layer in the
atmosphere.
The thermosphere lies above the mesosphere, starting at about 50 miles above
sea level. This layer is often called the “upper atmosphere.” Any person traveling
at an altitude of more than 50 miles above sea level is considered an astronaut.
Space shuttles and some satellites orbit the Earth within this layer. The thermosphere also is the layer in which auroras take place. The Earth's thermosphere is
the layer of the atmosphere which is first exposed to the Sun's radiation and so is
first heated by the Sun. The air is so thin that a small increase in energy can
cause a large increase in temperature. This layer is the hottest layer in the
atmosphere. Temperatures increase with altitude in the thermosphere.
The ionosphere is a name often given to the combination of the mesosphere
and the thermosphere. In both these layers, free ionic particles can be found.
The ionosphere is important because it reflects radio waves, enabling much of
our long- distance communication.
The exosphere is the outermost atmospheric layer. It has no definite outer limit,
as it merges with space. Many satellites orbit the Earth within the exosphere,
usually at altitudes of from 300 to 600 miles above sea level. The temperature of
the exosphere decreases as the altitude increases.
After reading the background information complete the data table below
Atmospheric Layer
Troposphere
Stratosphere
Mesosphere
Thermosphere
Ionosphere
Exosphere
Based on the background information, list important
characteristics of each layer
Atmospheric Layer
Describe what happens to the temperature as altitude
increases.
Troposphere
Stratosphere
Mesosphere
Thermosphere
Exosphere
Match each layer with its description.
_______ exosphere
A. closest to Earth, where almost all weather is created
______ ionosphere
B. mesosphere plus thermosphere; reflects radio waves
_______ mesosphere
C. furthest from Earth; hosts the most satellites
_______ ionosphere
D. too high for aircraft, but too low for satellites
_______ thermosphere
E. hosts a few clouds and the ozone layer
_______ stratosphere
F. hosts the space shuttle and some satellites
List the percentage of each gas found in the atmosphere
Nitrogen ______
Oxygen ______
Other particles ______
Label the atmospheric layers and draw things you may find in each layer.