essay on structure of atmosphere
Answers
Earth’s atmosphere is composed of about 78% nitrogen, 21% oxygen, and 0.93% argon. The remainder, less than 0.1%, contains such trace gases as water vapor, carbon dioxide, and ozone. All of these trace gases have important effects on Earth’s climate. The atmosphere can be divided into vertical layers determined by the way temperature changes with altitude. The layer closest to the surface is the troposphere, which contains over 80% of the atmospheric mass and nearly all the water vapor. The next layer, the stratosphere, contains most of the atmosphere’s ozone, which absorbs high-energy radiation from the sun and makes life on the surface possible. Above the stratosphere are the mesosphere and thermosphere. These two layers include regions of charged atoms and molecules, or ions. The upper mesosphere and lower thermosphere are called the ionosphere, this region is important to radio communications, because radio waves can bounce off the layer and travel great distances. It is thought that the present atmosphere developed from gases ejected by volcanoes. Oxygen, upon which all animal life depends, probably accumulated as excess emissions from plants that produce it as a waste product during photosynthesis. Human activities may be affecting the levels of some important atmospheric components, particularly carbon dioxide and ozone.
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