2 Summarize the structure and composition of the atmosphere. Atmospheric BasicsLearning TargetI can:Summarize the structure and composition of the atmosphere.
3 Atmospheric Composition Atmospheric BasicsAtmospheric CompositionAir is a mixture of many gases, each with its own unique characteristics.About 99 percent of the atmosphere is composed of nitrogen and oxygen, with the remaining one percent consisting of small amounts of argon, hydrogen, carbon dioxide, water vapor, and other gases.
8 Atmospheric Composition Atmospheric BasicsAtmospheric CompositionLower Atmospheric LayersThe troposphere, the layer closest to Earth’s surface, contains most of the mass of the atmosphere, including water vapor.Most weather takes place in and most air pollution collects in the troposphere.The troposphere is characterized by a general decrease in temperature from bottom to top.The upper limit of the troposphere, called the tropopause, varies in height.
9 Atmospheric Composition Atmospheric BasicsAtmospheric CompositionLower Atmospheric LayersThe stratosphere, which is above the tropopause, is a layer made up primarily of concentrated ozone.The stratosphere is heated because ozone absorbs ultraviolet radiation, and air gradually increases in temperature to the top of the layer, called the stratopause.
10 Atmospheric Composition Atmospheric BasicsAtmospheric CompositionUpper Atmospheric LayersThe mesosphere is above the stratosphere. Temperature drops in this layer due to lower pressure and thinning air.The thermosphere increases in temperature due to exposure to intense solar radiation.
11 Atmospheric Composition Atmospheric BasicsAtmospheric CompositionUpper Atmospheric LayersThe ionosphere, which is made up of electrically charged particles and layers of progressively lighter gases, is part of the thermosphere.The exosphere, which is composed of light gases such as helium and hydrogen, is the outermost layer of Earth’s atmosphere.There is no clear boundary between the atmosphere and space.