Scientists identify flank instability at a volcano with history of collapse Landslides caused by the collapse of unstable volcanoes are one of the major dangers of volcanic eruptions. A method to detect long-term movements of these mountains using satellite images could help identify previously overlooked instability at some volcanoes, according to Penn State scientists. “Whenever there is a large volcanic eruption, there is a chance that if a flank of the volcano is unstable there could be a collapse,” said Judit Gonzalez-Santana, a doctoral student in the Department of Geosciences. “To better explore this hazard, we applied an increasingly popular and more sensitive time-series method to look at these movements, or surface deformation, over longer time periods.”