The "hole" in the ozone layer refers to a significant thinning of the ozone layer, particularly over Antarctica, which occurs each spring (from September to November). The ozone layer is a region of the Earth's stratosphere that contains a high concentration of ozone (O₃) molecules and plays a crucial role in protecting life on Earth by absorbing the majority of the Sun's harmful ultraviolet (UV) radiation.
The primary cause of the depletion of ozone in this region is the release of chlorofluorocarbons (CFCs) and other ozone-depleting substances (ODS) into the atmosphere. When these substances reach the stratosphere, they are broken down by UV radiation, releasing chlorine atoms. These chlorine atoms can react with ozone, leading to its destruction.
The "hole" does not represent a complete absence of ozone but rather a significant reduction in ozone concentrations, leading to increased levels of UV radiation reaching the Earth's surface, which can have harmful effects on human health, ecosystems, and wildlife. International efforts, such as the Montreal Protocol established in 1987, have led to significant reductions in the use of many ozone-depleting substances and have contributed to the gradual healing of the ozone layer.