Percy Bysshe Shelley I MET A TRAVELLER from an antique land
Who said: Two vast and trunkless legs of stone
Stand in the desert. Near them on the sand,
Half sunk, a shattered visage lies, whose frown
And wrinkled lip and sneer of cold command
Tell that its sculptor well those passions read
Which yet survive, stamped on these lifeless things,
The hand that mocked them and the heart that fed.
And on the pedestal these words appear:
"My name is Ozymandias, King of Kings:
Look on my works, ye mighty, and despair!"
Nothing beside remains. Round the decay
Of that colossal wreck, boundless and bare,
The lone and level sands stretch far away
Importance of the Atmosphere (1) The Earth is surrounded by an
ocean of gases we call the atmosphere. The atmosphere is important because it
contains the air most living things
breathe. It also absorbs heat energy and
dangerous rays from the sun. It even
recycles water. Without the atmosphere,
life as we know it could not exist on Earth.
The Layers of the Atmosphere
(2) The atmosphere extends about 600
kilometres above the surface of the
Earth. Scientists have discovered it is
divided into layers, just like a layer cake.
The names and number of layers are
pictured in the diagram to the right. As
you can see, each layer varies in
thickness and in temperature. They also
differ in composition - the types of gases they contain.
The Troposphere
(3) The layer of the atmosphere we live in is called the Troposphere. Tropo is a Greek word meaning turning or change. This first layer
begins at sea level and ends between 8 and 15 kilometres up. The
Troposphere contains about 50% of all the air in the entire atmosphere. Because it is at the bottom, air pressure (the weight of
the air) is greatest in this layer. All the clouds we see and the changes
in weather we experience occur in the Troposphere.
