layer peaks at 8 to 15 parts per million of ozone, while the average ozone concentration in Earth's atmosphere as a whole is about 0.3 parts per million. The ozone layer is mainly found in the lower portion of the stratosphere, from approximately 15 to 35 km above Earth, although its thickness varies seasonally and geographically.

The ozone layer was discovered in 1913 by French physicists Charles Fabry and Henri Buisson.