1. The Atmosphere Chapter 15 Section1

2. Composition of the Atmosphere The most abundant gas in the atmosphere that we breathe is Nitrogen 78% Nitrogen The second most abundant gas in the atmosphere is Oxygen 21% Oxygen The remaining gases amount to less than 1% of the atmosphere The atmosphere is a mixture of gases that surrounds the Earth

3. Atmospheric Pressure Air pressure is the measure of the force with which the air molecules push on a surface Air pressure changes with altitude Altitude is the height of an object above the Earth’s surface The closer or lower you are in the atmosphere the more pressure that is exerted on you. The higher you move into the Earth’s atmosphere the lower the pressure you will feel. The pressure on the Earth’s surface is measured with a barometer

4. Layers of the Atmosphere Based on temperature, the Earth’s atmosphere is divided into four layers By the way did I say the layers are based on temperature.

5. Troposphere The troposphere lies next to the Earth’s surface It is the densest layer of the atmosphere This is the layer that we live in This is the layer that all the weather forms As you move up through the troposphere the temperature and air pressure drops

6. Stratosphere The layer just above the troposphere is called the stratosphere In the stratosphere the air is very thin and contains little moister The lower part is very cold -60 Celsius The temperature is high in the upper part of the stratosphere The upper part of the stratosphere has an area called the ozone Ozone is a molecule that is made up of three oxygen atoms The ozone absorbs ultraviolet radiation, warming the air The ozone protects the life on Earth

7. Mesosphere The mesosphere is just above the stratosphere The mesosphere is the coldest layer of the atmosphere The mesosphere get cooler as you move to the upper part of it

8. Thermosphere Just above the mesosphere is the thermosphere The thermosphere is the upper most part of the atmosphere In this part of the atmosphere the temperature rises as you move up through it Temperatures in this layer can reach 1,700 Celsius If you could stand in the thermosphere you would not feel hot

9. Ionosphere The upper part of mesosphere & lower part of the thermosphere is the ionosphere Nitrogen & oxygen atoms absorb X rays and gamma rays This causes the particles to become electrically charged, electrically charged particles are called ions Ions radiate energy as light (Aurora borealis) It also reflects some radio signals like am radio back to Earth