Environmental Protection Agency (EPA) MVAC Certification

What natural phenomenon is a cause of ozone layer depletion?

1. Volcanic eruptions

2. Rainforest deforestation

3. Ocean pollution

4. Urbanization

The correct answer is: Volcanic eruptions

Volcanic eruptions are indeed a natural phenomenon that can contribute to ozone layer depletion. When volcanoes erupt, they release various gases and particulates into the atmosphere, including sulfur dioxide. This gas can lead to the formation of sulfate aerosols, which, while they can contribute to atmospheric cooling, can also have complex interactions with ozone molecules. The more significant concern regarding ozone depletion primarily comes from human-made substances, like chlorofluorocarbons (CFCs); however, volcanic eruptions can still add to the complexity of atmospheric chemistry and influence ozone levels in the natural context. The other options—rainforest deforestation, ocean pollution, and urbanization—while they can have environmental impacts, are not recognized as direct causes of ozone layer depletion specifically. Deforestation typically impacts climate regulation and carbon cycle, ocean pollution affects marine ecosystems, and urbanization contributes to air pollution and local climates, but none of these phenomena are primary drivers in the depletion of the ozone layer compared to natural volcanic activity.