The gaseous mass or envelope of air surrounding the Earth is termed as atmosphere. This is further sub divided into the troposphere, stratosphere, mesosphere and thermosphere. . It is a very important place where climatic changes, rainfall etc take place. Atmosphere ensures the continuity of life on earth by blocking the harmful UV rays of the sun and by burning down\slowing meteors crashing into Earth.
Atmosphere plays an important role in many important cycles like the Carbon cycle, the water cycle and the nitrogen cycle. Troposphere is region of the atmosphere closest to the Earth. It extends from the surface up to about 10 km in altitude. Almost all weather takes place in the troposphere. Mt. Everest, the highest mountain on Earth, is only 8.8 km high. Temperatures decrease with altitude in the troposphere. As warm air rises, it cools, falling back to Earth. This process, known as convection, means there are huge air movements that mix the troposphere very efficiently. Stratosphere is the region of the atmosphere above the troposphere. Stratosphere extends from about 10km to about 50km in altitude. Commercial airlines fly in the lower stratosphere. The stratosphere gets warmer at higher altitudes. In fact, this warming is caused by ozone absorbing ultraviolet radiation. Warm air remains in the upper stratosphere, and cool air remains lower, so there is much less vertical mixing in this region than in the troposphere. Stratosphere is important for life on earth because it is home to the ozone layer. Ozone is the gas composed of three atoms of oxygen. Ozone is a pollutant at ground level. Nearly 90% of the Earth's ozone is in the stratosphere and is referred to as the ozone layer. Ozone absorbs a band of ultraviolet radiation called UVB that is particularly harmful to living organisms. The ozone layer prevents most UVB from reaching the ground. The stratospheric layer composed of a form of oxygen with three atoms to the...