1. Geosphere or

2. Atmosphere The surrounding air of the Earth

3. Composition of Air There are many different types of gasses in the atmosphere They include nitrogen, oxygen, argon, carbon dioxide and other noble gasses The gas that is most abundant is nitrogen

4. Properties of Air Air has mass, therefore, in a given volume, it has density. If there are more molecules in a given volume, the density is greater. If there are fewer molecules, the density is less. Air Pressure is the result of the weight of a column of air pushing down on an area. Denser air exerts more pressure than less dense air.

5. Altitude and the Properties of Air Altitude, or elevation, is the distance above sea level. Air pressure decreases as altitude increases. As air pressure decreases, so does density. We measure air pressure with a barometer in units called “inches of mercury” or “millibars”.

6. What is pushing down on us? Layers of the atmosphere There are 4 layers in the atmosphere They are the --troposphere --stratosphere --mesosphere --thermosphere

7. Troposphere This is the layer that is closest to the surface of the earth It’s elevation ranges from 0 to 10 km It’s the shallowest of the layers. The layer where weather occurs. It contains almost all of the mass of the atmosphere.

8. Stratosphere This layer sits on top of the troposphere It’s elevation ranges from 10 km to around 25 km This layer contains the ozone layer, which protects us from harmful sunlight The lower stratosphere is colder than the upper stratosphere.

9. Mesosphere This layer is above the stratosphere It’s elevation ranges from 25 to 100 km It protects the Earth’s surface from being by most meteoroids.

10. Mesosphere from space

11. Thermosphere This is the highest layer of the atmosphere It’s height ranges from 100 to 400 km It is divided into two layers: –Ionosphere : This is where most small meteorites burn up and is also the location in the atmosphere that the northern lights occur (aurora borealis) –Exosphere : is the outer portion of the thermosphere and extends all the way into outer space.