The Ozone Layer
Ozone shields us from UV radiation.
About this topic
The ozone layer, in the stratosphere about 15–35 km up, contains O₃, which absorbs most of the Sun's harmful UV-B and UV-C radiation, protecting people from skin cancer and cataracts and protecting ecosystems. Chlorofluorocarbons (CFCs) from aerosols and refrigerators release chlorine that destroys ozone, creating the "ozone hole" over Antarctica.
The 1987 Montreal Protocol banned CFCs, and the layer is slowly recovering, a success of international cooperation. Ground-level ozone, in contrast, is a pollutant.
Picture the ozone layer as sunscreen for the planet. If all the ozone were compressed to sea-level pressure, it would be a layer only about 3 mm thick, yet it absorbs the vast majority of dangerous UV. Ozone is continually made and destroyed in the Ozone-Oxygen cycle, in which UV splits O2 into atoms that join other O2 molecules. A single chlorine atom can destroy tens of thousands of ozone molecules as a catalyst, which explains why small amounts of CFCs did so much damage.
The hole forms each Southern Hemisphere spring because polar stratospheric clouds in the cold Antarctic winter help chlorine become active when sunlight returns. Thanks to the Montreal Protocol, scientists expect the ozone layer to recover to 1980 levels around the middle of this century. Wearing sunscreen, hats and the UV index remain relevant. A common misconception is that the ozone hole is a literal hole or the main cause of global warming; it is a region of thin ozone. Another is that all ozone is good; near the ground it is smog and harms lungs and crops.
Key ideas
- CFCs damaged it
- Montreal Protocol helped recovery
- Found in the stratosphere
Quick check
Use cases: where The Ozone Layer helps
- Homework: review the key idea behind The Ozone Layer before you start a problem set.
- Exam revision: use the quick check to test whether you can recall The Ozone Layer without notes.
- Visual learning: play with the interactive lab to see how The Ozone Layer changes when you adjust its inputs.
- Teaching a friend: explain The Ozone Layer in your own words, then compare your version with the key ideas.
Earth science helps with weather forecasts, natural hazards, energy and climate planning.
Frequently asked questions
What is The Ozone Layer?
Ozone shields us from UV radiation.
What will I learn in The Ozone Layer?
CFCs damaged it. Montreal Protocol helped recovery. Found in the stratosphere.
Is The Ozone Layer part of Earth & Space?
Yes. It is one of 60 Earth & Space topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the The Ozone Layer lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study The Ozone Layer?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.