 Ranges from 0 km to 12 km  Lowest layer of the atmosphere  Where we live  Where almost all of the Earth’s weather occurs  “Tropo” means turning or changing; named because conditions are always changing  Shallowest layer of the atmosphere with almost all of the mass of the entire atmosphere  As altitude increases, temperature drops. Why?  Because the air gets less dense as altitude increases.

 Ranges from 12 km to 50 km  “Strato” means layer or spreading out  The ozone layer is located in the upper stratosphere, and it protects the Earth by absorbing and filtering out the sun’s harmful U-V rays.  As altitude increases, temperature increases. Why?  The upper stratosphere contains the ozone layer which absorbs energy and turns it into heat causing the temperature to be greater in the upper stratosphere.

 Ranges from 50 km to 80 km  Middle layer of the atmosphere  “Meso” means middle  protects the Earth from most meteors  As altitude increases, temperature drops. Why?  The lower mesosphere is closer to the ozone layer (hot) and the air gets less dense with altitude so it gets colder.

 Ranges from 80 km and beyond  very thin air  “Thermo” means heat  Broken into 2 layers- The Ionosphere and the Exosphere  As altitude increases, temperature increases. Why?  Although the air is very thin, the molecules are the first to receive energy from the sun, so the molecules are very hot.

 Is the lower portion of the Thermosphere  Ranges from 80 km to 550 km  where gas molecules become electrically charged particles called ions  Radio waves bounce off ions and back to Earth  Where the Aurora borealis is found (Northern Lights)

 Is the outer portion of the Thermosphere  Ranges from 550 km to outer space  “Exo” means outer  satellites orbit here