APES Textbook Ch 19

atmosphere

a thin envelope of gases surrounding the earth

atmospheric pressure

the force, or mass, per unit area of a column of air. This force is caused by the bombardment of a surface such as your skin by air molecules

• Atmospheric pressure decreases with altitude because there are fewer gas molecules at higher altitudes.

troposphere

the atmospheric layer closest to the earth’s surface.

• This layer extends only about 17 kilometers (11 miles) above sea level at the equator and 8 kilometers (5 miles) over the poles. If the earth were the size of an apple, this lower layer containing the air we breathe would be no thicker than the apple’s skin

• a dynamic system involved in the chemical cycling of the earth’s vital nutrients

• Its rising and falling air currents and winds are largely responsible for the planet’s short-term weather and long-term climate

stratosphere

extends from about 17 to about 48 kilometers (from 11 to 30 miles) above the earth’s surface (Figure 18-3).

• Although the stratosphere contains less matter than the troposphere, its composition is similar, with two notable exceptions: its volume of water vapor is about 1/1,000 that of the troposphere, and its concentration of ozone (O3) is much higher.

ozone layer

Much of the atmosphere’s small amount of ozone (O3) is concentrated here.

• Found roughly 17–30 kilometers (11–19 miles) above sea level

Air pollution

the presence of chemicals in the atmosphere in concentrations high enough to harm organisms, ecosystems, or human-made materials. The effects of air pollution range from annoying to lethal.

Primary pollutants

harmful chemicals emitted directly into the air from natural processes and human activities

secondary pollutants

when some primary pollutants react with one another and with the basic components of air to form new harmful chemicals