Volcanic gases

Part of Hall of Planet Earth.

In the Museum’s Hall of Planet Earth, a board with text, photo, and line graph explaining the composition and effects of volcanic gases. AMNH/R.Mickens

Volcanic gases are composed mainly of water, carbon dioxide, and sulfur dioxide. During violent eruptions, these gases are injected into the stratosphere. There, the sulfur dioxide reacts with water to form microscopic droplets, or aerosols, of sulfuric acid. The aerosols block sunlight from reaching the Earth’s surface, causing cooling. Sulfurous aerosols, along with chlorine, contribute to the destruction of stratospheric ozone, though most of this depletion comes from man-made chemicals.