Activity 5 — Volcanoes and the Atmosphere
Background Information
Volcanic Gas
All magmas contain dissolved gases that are released into the atmosphere during and between eruptions. Water vapor is the most abundant gas released, followed by carbon dioxide and sulfur-containing gases (predominantly sulfur dioxide and hydrogen sulfide). Magma also releases minor amounts of other gases such as hydrogen, carbon monoxide, hydrogen chloride, and hydrogen fluoride. The two volcanic gases most hazardous to people, animals, crops, and property are sulfur dioxide and carbon dioxide. Sulfur dioxide gas combines with water and oxygen to form sulfuric acid, and leads to abnormal acid rain downwind from a volcano. Large explosive eruptions that inject tremendous volumes of ash and sulfur dioxide gas into the stratosphere can contribute to temporary global cooling. Because carbon dioxide gas is heavier than air and collects in topographically low areas, people and animals in these low areas may suffocate and vegetation may die. Also, a few historic eruptions have released sufficient fluorine-compounds gas to deform or kill animals grazing in areas of ash fall; the fluorine compounds tend to be concentrated on fine-grained ash particles.
The EarthComm web site www.agiweb.org/earthcomm contains a variety of links to web sites that will help you deepen your understanding of content and prepare you to teach this activity. Many of the sites also contain images which can be downloaded and made into overheads for incorporation into class discussions. |