Long-term monitoring on active volcanoes. Time relationship between surface variations of temperature and changes of energy release from magmatic sources, verified by multi-parameter and interdisciplinary comparisons

Abstract:

The longest records of temperature data from active volcanoes in southern Italy are presented. One dataset comes from continuous monitoring of fumaroles temperature of la Fossa cone of Vulcano (Aeolian Islands), it runs from 1990 to 2014, but the first measurements started in 1984. Another dataset is from thermal aquifers of Mount Etna volcano, since 1989 the acquisition period has been one month, more recently data with hourly frequency are registered on the continuous monitoring network. Both monitoring systems are still ongoing. In 1984 at Vulcano the monitoring of fumaroles suffered of a pioneering approach, our technicians faced for the first time with extreme condition, absence of energy power, temperature range covering up to 2 order of magnitude (from normal ambient to several hundreds °C), steam, corrosive acidic fluids released by fumaroles (Sulphur and Chlorine compounds, Carbon dioxide). The experience matured in the high temperature fumarole field of Vulcano can be useful to support new surveillance programs on other volcanoes around the world. Time series analysis applied to fumaroles temperature highlighted the cyclic character of the main observed variations and major trends, lasting some years. Long term monitoring allowed comparisons of many temperature subsets with other validated geochemical and geophysical dataseries and highlighted common source mechanisms accounting for endogenous processes. Changes in the magma source and/or seismo-tectonic activity are the primary causes of the main time variations. A similar comparative approach has been applied to time series of temperature data recorded on Etna volcano. Time relationships have been found with the eruptive activity, particularly with the emission rates of volcanic products, although the monitoring sites are far from the eruptive vents. The collected data show confirmation about the effectiveness of the geochemical approach to follow in real time changes from the source, even being far from estimation of magmatic energy release retrieved by surface temperature monitoring.