Fig. 3
From: Understanding and forecasting phreatic eruptions driven by magmatic degassing
Reproduced with permission from de Moor et al. (2016a) and used courtesy of the American Geophysical Union
High-resolution gas monitoring at Turrialba in 2014 and 2015. Note the increases in CO2/ST prior to ash emission events. Note water-rich gas plumes in phases 1–3 (photos). The disappearance of H2S in early March 2015 marks the rapid transition from hydrothermally influenced to purely magmatic degassing, interpreted to reflect expulsion of the hydrothermal system and conduit opening.