Sulfur dioxide emissions and degassing behavior of Erebus volcano, Antarctica

Abstract

Emission rates of sulfur dioxide (SO 2) were measured at Erebus volcano, Antarctica in December between 1992 and 2005. Since 1992 SO 2 emissions rates are normally distributed with a mean of 61 ± 27 Mg d − 1 (0.7 ± 0.3 kg s − 1 ) ( n = 8064). The emission rates vary over minutes, hours, days and years. Hourly and daily variations often show systematic and cyclic trends. Long-wavelength, large amplitude trends appear related to lava lake area and both are likely controlled by processes occurring at depth. Time series analysis of continuous sequences of measurements obtained over periods of several hours reveals periodicity in SO 2 output ranging from 10 to 360 min, with a 10 min cycle being the most dominant. Closed and open-system degassing models are considered to explain observed variable degassing rates. Closed-system degassing is possible as rheological stiffening and stick/slip may occur within the system. However, the timescales represented in these models do not fit observations made on Erebus. Open-system degassing and convection fits the observations collected as the presented models were developed for a system similar to Erebus in terms of degassing, eruptive activity and process repose time. We show that with the observed emission rate (0.71 kg s − 1 ) and a crystal content of 30%, magma will cool 65 °C to match observed heat fluxes; this cooling is sufficient enough to drive convection.