Final answer:
Ozone depletion is primarily caused by human activities, but natural processes such as volcanic eruptions also contribute to it. Sulfur aerosols released during volcanic eruptions break down ozone-depleting substances, while nitrous oxide can also reach the stratosphere and contribute to ozone depletion.
Step-by-step explanation:
Ozone depletion is primarily caused by human activities, but there are natural processes that also contribute to it. One of these natural processes is the breakdown of ozone molecules by volcanic eruptions, which release sulfur aerosols into the atmosphere. The sulfur aerosols break down ozone-depleting substances, such as chlorofluorocarbons (CFCs) and halon, resulting in the release of chlorine and bromine gases that deplete ozone molecules. Additionally, nitrous oxide has become a major chemical that can reach the stratosphere and contribute to the ozone depletion process.