The Ozone Layer Explained
Understanding the thin shield that protects all life on Earth.
What is the ozone layer?
The ozone layer is a region of Earth's stratosphere, roughly 15 to 35 kilometres above the surface, that contains a high concentration of ozone (O₃) molecules. Despite being only a few millimetres thick if compressed to surface pressure, this layer absorbs 97–99% of the Sun's medium-frequency ultraviolet light (UV-B), which is potentially damaging to life on Earth.
How does it protect us?
UV-B radiation can cause skin cancer, cataracts, and immune suppression in humans, harm marine ecosystems and phytoplankton, reduce agricultural yields, and degrade plastics and other materials. The ozone layer acts as a natural sunscreen, absorbing this harmful radiation before it reaches the surface.
How is it formed?
Ozone is continuously created and destroyed in the stratosphere by the Chapman cycle. UV radiation splits oxygen molecules (O₂) into individual atoms, which then combine with other O₂ molecules to form ozone (O₃). Ozone itself absorbs UV, splitting back into O₂ and O. In an undisturbed atmosphere, this cycle maintains a stable ozone concentration.