Which layer of Earth's atmosphere contains the ozone layer?

• A. Stratosphere
• B. Troposphere
• C. Mesosphere
• D. Exosphere

Answer: (A)

The ozone layer is located in the stratosphere, the second major layer of Earth’s atmosphere above the troposphere. In this region, ultraviolet radiation from the Sun splits oxygen molecules and helps form ozone (O3), which then concentrates there. The stratosphere also warms with height due to ozone absorbing UV light, creating a stable zone where ozone can accumulate. The troposphere, where weather occurs, is nearer the surface and generally has less ozone. The mesosphere lies above the stratosphere and is cooler with much less ozone, while the exosphere is the outermost, extremely thin layer with almost no ozone.