A study of volcanic activity and its effects on the atmosphere is one of 28 interdisciplinary investigations, for the Earth Observing System (EOS), due to be launched in 1997 and 1999. The volcanology investigation will include long- and short-term monitoring of selected volcanoes, the detection of precursory activity associated with unanticipated eruptions, and the detailed study of on-going eruptions. The data collected will allow us to address two aspects of volcanism: volcanic padforms and the atmospheric effects of eruptions. A variety of instruments on the two NASA EOS platforms, together with supplemental data from the Japanese and European platforms, will enable the study of local- to regional-scale thermal and deformational features of volcanoes, and the chemical and structural features of volcanic eruption plumes and aerosols. This investigation fits well within the overall goal of the EOS Project, which is to study the regional and global interrelationships between components of the Earth System, because it specifically investigates the links between volcanism, atmospheric chemistry and short-term (1-3 year) climate change.