| A | B |
|---|
| pressure | amount of force pressing down on an area |
| atmosphere | a thin layer of air made up of many gases that forms a protective covering around the planet |
| troposphere | layer of Earth's atmosphere that is closest to the ground, contains 99% of the water vapor and 75% of the atmospheric gases; where clouds and weather occur |
| ionosphere | layer of electrically charged particles in the thermosphere that absorbs AM radio waves during the day and reflects them back at night |
| ozone layer | layer of the stratosphere with a high concentration of ozone; absorbs most of the Sun's harmful ultraviolet radiation |
| ultraviolet radiation | a type of energy that comes to Earth from the Sun, can damage skin and cause cancer, and is mostly absorbed by the ozone layer |
| chlorofluorocarbons (CFCs) | group of chemical compounds used in refrigerators, air conditioners, foam packaging, and aerosol sprays that may enter the atmosphere and destroy ozone |
| stratosphere | layer above the troposphere that extends from 10 km above Earth's surface to 50 km; contains ozone |
| mesosphere | atmospheric layer above stratosphere that extends to about 85 km above Earth's surface |
| thermosphere | thickest atmospheric layer found between 85 km and 500 km above Earth's surface; named for its high temperatures |
| exosphere | top layer of atmosphere beginning at 500 km above Earth's surface; beyond this layer is outer space |
