Volcanic gas

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Augustine Volcano Jan 12 2006

Sketch showing typical CO2 emission patterns from volcanic and magmatic systems

Summit crater of Villarrica, Chile

Volcanic injection

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Vog from Sulfur dioxide emissions

Volcanic gas refers to the gases emitted from a volcano during an eruption or from diffuse emissions such as volcanic fumaroles. These gases originate from the magma and are released into the atmosphere as the magma rises to the surface and degasses. The composition of volcanic gas can vary significantly but typically includes water vapor (H₂O), carbon dioxide (CO₂), sulfur dioxide (SO₂), hydrogen sulfide (H₂S), carbon monoxide (CO), hydrogen chloride (HCl), hydrogen fluoride (HF), and a variety of minor and trace gases including noble gases and volatile metals.

Composition and Emission

The primary components of volcanic gases are water vapor, carbon dioxide, and sulfur dioxide. Water vapor is the most abundant volcanic gas, constituting about 60% to 90% of the total emissions. Carbon dioxide is the second most common gas, followed by sulfur dioxide, which can have significant environmental and climatic impacts due to its ability to form sulfuric acid in the atmosphere, leading to acid rain and cooling effects on the global climate.

Volcanic gases are emitted from various sources, including the main vent during an eruption, through ground cracks, and from fumaroles, which are openings in the Earth's crust that emit steam and gases. The release of these gases can pose significant hazards, not only directly from toxic exposure but also by contributing to volcanic smog (vog) and acid rain, which can affect air quality and have health implications for humans and animals, as well as impacts on water quality and vegetation.

Environmental and Climatic Impact

Volcanic gases can have profound impacts on the environment and climate. For example, sulfur dioxide (SO₂) emitted during volcanic eruptions can lead to the formation of sulfate aerosols in the stratosphere, which reflect sunlight and can cause global cooling. This phenomenon was observed after the 1991 eruption of Mount Pinatubo, which resulted in a measurable cooling of the Earth's surface for a period of up to two years.

In addition to climatic effects, volcanic gases can also have direct impacts on the environment. Acid rain, resulting from the dissolution of sulfur dioxide and other acidic gases in the atmosphere, can lead to soil and water acidification, affecting agriculture and water resources. Volcanic smog, or vog, created by the reaction of volcanic gases with sunlight and atmospheric oxygen, can reduce air quality and visibility, and pose health risks to humans and animals.

Monitoring and Mitigation

Monitoring volcanic gases is crucial for volcanic hazard assessment and eruption forecasting. Techniques for monitoring gases include direct sampling from fumaroles, remote sensing using satellites, and ground-based spectroscopy. By analyzing changes in gas composition and emission rates, scientists can gain insights into the movement of magma beneath a volcano and the likelihood of an eruption.

Mitigation of the impacts of volcanic gases involves measures such as evacuation of affected areas, use of masks or respirators to protect against inhalation of harmful gases, and the development of early warning systems to alert populations of increased volcanic activity and gas emissions.

See Also

• Volcanology
• Volcanic eruption
• Environmental impact of volcanic eruptions