The atmosphere is divided into different regions, called layers. The layer closest to the surface is known as troposphere, after which comes the stratosphere. The stratosphere begins at an altitude of 10 miles above the surface of the earth and stretches up to 31 miles above the surface of the earth. It is the second layer of the atmosphere (beginning from the surface of the earth) and it is the region which contains ozone, which plays a vital role in stopping ultraviolet radiation from reaching the earth's surface.