Volcanic gases

VOLCANIC GASES (EN: volcanic gases; DE: Vulkangase; FR: gaz volcaniques; ES: gases volcanicos; RU: вулканические газы) are the gases, which are released during and after the eruption from the crater, from the cracks, which are situated on the slopes of the volcanoes, from the lava flows and pyroclastic rocks. Within the composition of these gases, besides the H2O vapour (more than 90% by volume), there have been identified: CO2, CO, CH4, H2S, SO2, H2, N2, HCl, HF, the noble and other gases, small quantities of the volatile compounds, prevalently of the halogens, with many chemical elements, including with various metals.

The volcanic gases, which are released during the eruption from the craters, boccas, and eruptive fissure vents, during the process of the degassing of the magma, which is rising to the surface, are called the eruptive gases; they determine the character of the explosive eruptions, and influence the ability to flow of the lavas, which are outpouring. The volcanic gases, which are released during the periods of the calm activity of the volcanoes from the fumarole fields, in the form of the jets and swirling masses, from the individual places of the craters, or from the surface of the cooling lava flows, are called the fumarolic, mofetta, and solfatara gases, depending on the composition and temperature of the gases (see the "Fumaroles", "Mofette", and "Solfataras" articles); these gases represent by themselves the mixture of the gases, which have arrived from the lavas or pyroclastic rocks, with the gases, which have been captured from the atmosphere, and which have been formed during the interaction of the hot volcanic products with the rocks, soil, vegetation, ground waters, and other waters, which have been buried under these products.