ERUPTIVE AND DIFFUSE EMISSIONS OF CO2 FROM MOUNT ETNA

MOUNT Etna, in Sicily, is one of the world's most actively degassing volcanoes 1. Here we use data collected from 1975 to 1987 to estimate carbon dioxide emissions from the summit craters and the upper flanks of the volcano. By combining measurements of the SO2 flux in the plume (refs 1-6 and this paper) with measurements of the CO2/SO2 ratio of the plume gases, we find that the average output of CO2 from summit crater degassing is 13 +/- 3 Tg yr-1. This is an order of magnitude higher than the annual CO2 output from Kilauea 7,8, Hawaii, and representative arc volcanoes 9,10. Furthermore, we find that diffuse emissions of CO2 from the upper flanks of Etna are magma-derived and are of a similar magnitude to those emitted from the crater plume. This observation, as well as others 11-14, verifies the idea 15 that extensive diffuse release of magmatic CO2 may occur in volcanically active regions - a process that needs to be taken into account when evaluating the volatile budget of subaerial volcanism. Such degassing may be of use for monitoring volcanic activity, could provide a means for radiocarbon dating of eruptions, and may be a mechanism by which CO2 is injected into crater lakes.