2.  Gasses make up the air around us  Primary gasses are Nitrogen and Oxygen  Small amounts of many other gasses are present.

3. A. Troposphere (0km – 10km)  75% of all air in atmosphere  All weather takes place here  Temps warmer near Earth’s surface  Temp decreases as altitude increases B. Stratosphere (10km – 50km)  Temp increases with altitude  Contains most of Ozone Gas C. Mesosphere (50km – 200km)  Coldest layer in atmosphere  Temperature decreases with altitude D. Thermosphere (200km – 500km)  Air particles spread out  Particles disturbed by energy from Sun produce visible auras. 10km 50km 200km 500km