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Across 4. Alteration of the natural environment by natural or man-made sources creating harm to living organisms. 6. Radiation of higher frequencies than visible light, which can cause sunburn and other types of damage. 8. A colorless, highly flammable gas in rocket fuels, producing synthetic ammonia and methanol and in petroleum refining. Has the symbol "H" 9. A heavy, colorless gas. The fourth most abundant gas in the atmosphere. 10. A whitish, inert gas used in gas-dis-charge lamps and fluorescent lamps. Super Man is afraid of it. Has the symbol "Kr". 12. A half of a sphere bounded by a great circle. 13. Transfer on energy (heat) by direct contact. 14. A smooth and steady onward movement (e.g. water or a flow of electric charge). Flowing. Running. 15. A fast wind that flows west to east in the stratosphere. 16. A colorless, odorless inert gas. The third most abundant gas in teh atmosphere. 18. A process by which electromagnetic radiation is emitted or propagated through space by virtue of joint undulatory variation in the element electric amd magnetic fields. 21. The vertical distance above sea level. 22. The heating effect of the atmosphere caused by the absorbtion of heat by pollution gases. 23. The layer of the atmosphere that meteors burn in. 27. Outer most layer of the atmosphere. 28. Principal means of energy transfer by vertical motion. 29. A gas molecule that consists of three atoms.

Down 1. Synthetic compounds containing carbons and halogens that destroy the ozone. 2. A gaseous element found in television tubes and and fills the colorful bright light tubes found in Las Vegas. Has the symbol "Ne". 3. The layer of the atmosphere above the troposphere. 5. Layer of Earth's atmosphere that is closest to the ground; contains 99 percent of the water vapor and 74 percent of the atmospheric gases, and is where clouds and weather occur. 7. A colorless, odorless, highly unreactive gas found in small amounts. Has the symbol "Xe". 11. The layer of the atmosphere where temperature is the hottest. 17. In its free form, colorless, tasteless, and odorless gas. It is the second most abundant gas in the atmosphere. 19. Layer in the atmosphere with a high concentrations of ozone. 20. A colorless, odorless, flammable gas, the major component in natural gas and used as a fuel. Has the symbol "CH4". 21. The invisible envelop of air surrounding the planet earth. 24. A colorless, odorless, almost inert gas in various minerals, and in all proteins, nonmetallic. Most dominanat gas in the atmosphere. 25. A natural abundant nonmetallic element that occurs in many inorganic and in all organic compounds. Has the symbol "C". 26. A colorless, odorless, tasteless inert gas that provide lift for balloons.