3.2: The Atmosphere
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The Atmosphere
The atmosphere is a gaseous mass or envelope surrounding the Earth, and retained by the Earth's gravitational field. The Earth's atmosphere is subdivided into levels:
* The troposphere is the lowest portion (up to about 6-8 miles [10-13 km]) where all weather takes place and contains about 80% of the atmosphere's mass and 99% of its water vapor. |
* The overlying stratosphere extends up to about 31 miles (50 km). It contains an abundance of ozone which absorbs ultraviolet radiation, protecting life on land and in the shallow ocean . |
*The mesosphere is the part of the earth's upper atmosphere above the stratosphere in which temperature decreases with altitude to the atmosphere's absolute minimum. |
* The thermosphere the region of the atmosphere above the mesosphere and below the height at which the atmosphere ceases to have the properties of a continuous medium (about 60 miles [100 km]). The thermosphere is characterized throughout by an increase in temperature with height. Here where the charged atomic particles of the solar wind interacts with atmospheric gases. |
