Layers of the Atmosphere 6-4.1 Compare the composition and structure of Earth’s atmospheric layers (including the gases and differences in temperature and pressure within the layers).

Essential Question How do each of the layers of the Earth’s atmosphere compare to each other?

These are the layers in order from the Earth upwards Troposphere Stratosphere Mesosphere Thermosphere Exosphere

Create a saying to remember them Such as “Try sending me to the exosphere!”

The Troposphere Lowest layer. Weather occurs here and therefore clouds. We live in it. “Tropo” means turning or changing conditions. Densest layer. Temperature is warmer at the surface and decreases with altitude.

Temperature/Density and the Troposphere Troposphere: temperature at surface is warmed by the earth absorbing energy from the sun. Convection currents carry the heat upward, so the air cools as it rises. Density decreases since there is less air above.

The Stratosphere “Strato” means layer or spreading out Contains the ozone layer which absorbs energy and causes the temperature to rise. The ozone layer protects the surface from dangerous UV rays (ultraviolet radiation from the Sun).

Temperature and the Stratosphere Ozone, made of oxygen, absorbs ultraviolet radiation from the sun, causing the temperature to increase. Density still decreases.

The Mesosphere Drop in temperature marks beginning of mesosphere “Meso” means middle Most meteors burn up here

Temperature and the Mesosphere This layer does not absorb energy from the sun, so it starts to cool again. Without greenhouse gases, energy pretty much passes straight through!

The Thermosphere “Thermo” means heat Very hot (over 1000°C), but since air is so thin (not very dense) it would not feel warm at all. The space shuttle orbits here. So even though it is very hot (over 1000°C), it would feel cold because there are so few particles to transfer heat to you. It takes special instruments to measure the temperature.

Temperature and the Thermosphere Solar radiation first hits this layer, so the few particles that are here can gain lots of energy. They move rapidly, so they have a very high temperature. But the air is so thin here that it takes special instruments to measure the temperature accurately.

The Exosphere “Exo” means outer Extends for 1000’s of miles Satellites orbit here No definite edge Molecules gradually escape out into space

Atmospheric gases Two most common? Nitrogen is the most common Oxygen is the second most common These gases are found throughout all the atmospheric levels.

Atmospheric gases

Inflating example Air inside a ball pushes against the sides. The more air we put in a ball, the more the molecules push. So the pressure increases as we add air.

Air Pressure Air pressure is the result of the column of air that is above you. There is so much air above you that at sea level you have 14.7 lbs/in2 pushing on you. Gravity causes most of the air to be pulled down to the surface.

Why are we not crushed by air pressure? Air pressure is equal in all directions. So air pushes equally in all sides of us. The forces are balanced!

Altitude and Density As the air pressure decreases, the density of the air decreases. The air particles are not squashed together as tightly the higher one goes. This is caused by gravity! The air at sea level and at 6km has the same 21% oxygen, but at 6km there are fewer molecules, so you take in less oxygen with each breath.

A journey through the Atmosphere - YouTube.wmv