THE ATMOSPHERE (chapter 24.1)

ATMOSPHERE - the layer of gases that surrounds the Earth ATMOSPHERE - the layer of gases that surrounds the Earth. The atmosphere forms a protective boundary between the Earth and space which provides conditions suitable for life... protects Earth’s surface from meteorites and space debris as well as high energy radiation holds in heat and moderates Earth’s temperature provides gases essential for life (oxygen, nitrogen, carbon dioxide)

AIR PRESSURE - the force exerted by the weight of a column of air on a surface air pressure changes with altitude - as the altitude increases, the depth of the column of air above decreases, so the pressure decreases As the altitude increases, air pressure and density decrease air pressure is measured with a barometer

temperature decreases as altitude increases Scientists use variations in temperature to divide the atmosphere into four vertical layers... 1. TROPOSPHERE (0-12 km)- lowest layer of the Earth’s atmosphere - contains almost all of the atmosphere’s water vapor which are important in the formation of clouds and precipitation weather - the condition of the atmosphere in a particular place at a particular time temperature decreases as altitude increases

2. STRATOSPHERE (12-50 km)- layer above the troposphere temperature fairly constant up to 20 km - temperature increases with altitude (-57 - 0*C) the upper stratosphere is warmer than the lower due to the ozone layer - a region of high ozone concentration - ozone in a highly reactive gas composed of three oxygen atoms

temperature decreases as altitude increases 3. MESOSPHERE (50-80 km)- layer above the stratosphere temperature decreases as altitude increases meteoroids that enter the atmosphere burn up in the mesosphere

4. THERMOSPHERE (>80 km)- outermost layer of the atmosphere temperature increases rapidly with altitude (gas molecules in the thermosphere absorb solar radiation and move very fast, the temp is very high) ionosphere - not a distinct layer of the atmosphere - region of charged particles / ions that overlaps the lower thermosphere

The aurora occurs in the ionosphere a colorful display of light produced when charged particles from the sun are attracted to the Earth’s magnetic poles the particles cause ions in the ionosphere to glow