what gases are commonly released during a volcanic eruption
GAS COMPOSITION. Other than free oxygen, generated by photosynthesis, all atmospheric gases were derived from inside the earth and released by volcanic eruptions. The gaseous portion of magma varies from ~1 to 5% of the total weight. Water vapor constitutes 70-90%.
1 TOMS MEASUREMENTS -- On a more regional scale, t he distribution and amount of sulfur dioxide released into the stratosphere by volcanic eruptions can be measured by the total ozone mapping spectrometer (TOMS), which is a sensor originally sent aloft in 1979 aboard the Nimbus-7 and Meteor-3 satellites.