There are several ways in which volcanic gases are measured by scientists at the UAF Geophysical Institute and the Alaska Volcano Observatory. These methods include direct sampling, ground and air-based remote sensing, and satellite remote sensing. Each method is designed to determine either the gas composition or the gas flux (mass per unit time) from an actively degassing volcano. Scientists measure these gases to determine the type of magma (and therefore type of possible eruption) that lies below the surface. The animations here show different gas measurements and what is likely occurring below the surface.