National Geographic <br/><br/>
Atmosphere: On the Air 

 - Washington, D.C.  National Geographic Society  1993 
<br/><br/> An ocean of air completely surrounds Earth.  Extending from our feet to 1,000 Kilometers into space, the atmosphere acts as a shield for Earth, protecting it and making it possible for plants and animals to survive. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Atmosphere<br/>Air