| A | B |
|---|
| Weather | The condition of Earth;s atmosphere at a particular time and place. |
| Ozone | A form of oxygen that has three oxygen atoms in each molecule instead of the usual two. |
| Atmosphere | The mixture of gases that surrounds earth. The outermost of the four spheres into which scientsists divide Earth. |
| Air Pressure | A force that is the result of the weight of a column of air pushing down on an area. |
| Altitude | Elevation above sea level. |
| Troposphere | The lowest layer of earth's atmosphere, where wather occurs. |
| Stratosphere | The second-lowest layer of earth's atmosphere; the ozone layer is located in the upper parts of this sphere. |
| Mesosphere | The middle layer of Earth's atmosphere; the layer in which most meteoroids burn up. |
| Thermosphere | The outermost layer of Earth's atmosphere. |
| Exosphere | The outer layer of the thermosphere, extending outward into space. |
| Ionosphere | The lower part of the thermosphere, where electrically charged particles called ions are found. |
| aurora borealis | A colorful, glowing display in the sky caused when particles from the sun strike oxygen and nitrogen atoms in the ionosphere; also called the Northern Lights. |
| barometer | An instrument used to measure changes in air pressure. |
