The main gas produced by volcanic eruptions is water vapor, often accompanied by other gases like carbon dioxide, sulfur dioxide, and hydrogen sulfide. As magma rises to the surface, pressure decreases, causing dissolved gases to expand and escape, resulting in explosive eruptions. Water vapor can account for up to 90% of the emitted gases during certain eruptions. The presence of these gases plays a significant role in determining the eruption's violence and the formation of ash plumes. Understanding these gases and their effects is crucial for volcanic monitoring and predicting potential hazards.