A glacier is a mass of ice that moves or flows under its own weight in response to the pull of gravity.
Alpine glaciers are by far the most numerous today.
Atmospheric gases, volcanic ash, and other materials trapped in glacier ice provide a record of past conditions on earth. Possible consequences of global warming include changes in climate, melting of the ice caps, and a rise in sea level. Movements of air, or wind, take place in response to pressure differences in the atmosphere which are related to temperature differences. A desert is an extremely arid region that is incapable of supporting appreciable life. Most of the world's major deserts fall in belts close to 30 degrees north and south of the equator.