1. The Earth’s Atmosphere

2. Early Atmosphere
The early Atmosphere was very different then today's atmosphere
The early atmosphere was composed of out gassing from the volcanic activity of a young Earth.
These gasses were primarily Carbon Dioxide, Water Vapor, and Nitrogen
About 1 billion years ago Oxygen began to accumulate in the atmosphere allowing complex life to evolve

3. Modern Atmosphere
Earth’s atmosphere is made up of nitrogen, oxygen, carbon dioxide, water vapor, and many other gases, as well as particles of liquids and solids.
The modern atmosphere consists primarily of 2 gases
Nitrogen about 71% and Oxygen about 28%
The remaining 1 % is made up of a variety of gases of Which Argon is the most abundant

5. Layers of the Atmosphere
Troposphere begins at the surface and extends to between 7 km at the poles and 17 km ) at the equator.
The troposphere is mostly heated by the transfer of energy from the surface, so on average the lowest part of the troposphere is the warmest and temperature decreases with altitude.
The troposphere contains roughly 80% of the mass of the atmosphere. It also contains 99% of it’s water vapor and 75% of the gases that make up the atmosphere
The troposphere is where Earth’s weather occurs.

6. Layers Of the Atmosphere
The stratosphere is the next layer of the atmosphere
It is located directly above the troposphere.
It extends from 10 km to 50 km above earth’s surface.
It is very cold in the stratosphere and what ever water vapor is there turns to ice crystals
The stratosphere contains the Ozone layer which is a layer of O3 or an oxygen molecule with 3 atoms of oxygen.
The ozone layer protects Earth from the sun’s ultraviolet rays by absorbing them. Without the ozone layer Life on Earth could not exist as we know it.

7. Ozone Layer In the stratosphere is the ozone layer
Holes in the ozone layer were caused by man made chemicals Known as Chlorofluorocarbons or CFC.
These chemicals have been banned by the world leading to a decrease in the size of hole in the ozone layer.

8. Layers of the Atmosphere
The upper layers of the atmosphere contain the Mesosphere, Thermosphere and Exosphere
The mesosphere extends from 50km-85km and is the layer where meteors burn up in the atmosphere
The thermosphere is the hottest of all the layers of the atmosphere. It extends from 85km – 500km into space.
All of these layers have little mass meaning the gas molecules are very far apart.

9. Atmospheric pressure
Air pressure is the result of the weight of a column of air pushing down on an area.
The weight of the column of air above your desk is about the same as the weight of a large school bus! It doesn’t crush you because it pushing on you from all sides.
The air pressure at sea level is measured in square inches. It is apporximately14.7 pounds/per square inch.

10. Altitude and Air Density The density of air decreases as altitude increases. Air at sea level has more gas molecules in each cubic meter than air at the top of a mountain