Why is the ozone layer important to Earth?

Ozone is a coating of ozone in the Earth's atmosphere. The ozone layer is found between 9 and 25 miles up in the atmosphere and is caused by the interaction of sunlight with certain air molecules. While this blue-tinged gas is good for the atmosphere, it also creates a layer of chemical fog at ground level. Smog is a secondary pollutant formed by photochemical reactions of certain air pollutants, which are often produced by internal-combustion engines and industrial activity.

The ozone layer is critical to all life on Earth because it protects all living things from the Sun's harmful UV radiation. Scientists estimate that shallow water marine creatures generated oxygen around 2 billion years ago. This emitted oxygen contributed to the formation of the ozone layer. Ocean creatures developed as oxygen levels rose. Once the protective barrier in the atmosphere was in place, sea plants and animals could safely expand onto land. Because of the depletion of ozone, some delicate creatures, which are essential to the Earth's food chain, may be destroyed by the Sun's powerful UV radiation.