Editing Stratovolcano (section)

=== Volcanic gas ===
{{Main|Volcanic gas}}
As a volcano forms, several different [[Volcanic gas|gases]] mix with [[magma]] in the volcanic chamber. During an eruption the gases are then released into the [[atmosphere]] which can lead to toxic human exposure. The most abundant of these [[Volcanic gas|gases]] is [[Water|H<sub>2</sub>O]] ([[water]]) followed by [[Carbon dioxide|CO<sub>2</sub>]] ([[carbon dioxide]]), [[Sulfur dioxide|SO<sub>2</sub>]] ([[sulfur dioxide]]), [[Hydrogen sulfide|H<sub>2</sub>S]] ([[hydrogen sulfide]]), and [[Hydrogen fluoride|HF]] ([[hydrogen fluoride]]).<ref name=":04"/> If at concentrations of more than 3% in the air, when breathed in [[Carbon dioxide|CO<sub>2</sub>]] can cause dizziness and difficulty breathing. At more than 15% concentration [[Carbon dioxide|CO<sub>2</sub>]] causes death. [[Carbon dioxide|CO<sub>2</sub>]] can settle into depressions in the land, leading to deadly, odorless pockets of gas.<ref name=":06">{{Cite web|title=Volcanic gases can be harmful to health, vegetation and infrastructure {{!}} U.S. Geological Survey|url=https://www.usgs.gov/programs/VHP/volcanic-gases-can-be-harmful-health-vegetation-and-infrastructure|access-date=24 October 2024|publisher=United States Geological Survey}}</ref> [[Sulfur dioxide|SO<sub>2</sub>]] classified as a respiratory, skin, and eye irritant if come into contact with. It is known for its pungent egg smell and role in ozone depletion and has the potential to cause acid rain downwind of an eruption.<ref name=":06" /> [[Hydrogen sulfide|H<sub>2</sub>S]] has an even stronger odor than [[Sulfur dioxide|SO<sub>2</sub>]] as well as being even more toxic. Exposure for less than an hour at concentrations of over 500 ppm causes death.<ref name=":06" /> [[Hydrogen fluoride|HF]] and similar species can coat [[ash]] particles and once deposited can poison soil and water.<ref name=":06" /> Gases are also emitted during volcanic degassing, which is a passive release of [[gas]] during periods of dormancy.<ref name=":06" />