Preface: fluids and tectonics

The 8th International Conference on Gas Geochemistry provided the opportunity for scientists from different countries to meet each other, exchange ideas on the state of the art in gas geochemistry, and discuss advance in fluid geochemistry. The 8th ICGG meeting focused on three main geologic environments currently interacting with the human life: volcanoes, earthquakes and hydrocarbons. Ninety-four presentations gave participants chance to cover a variety of important research topics on gas geochemistry in geosciences including: gas migration in terrestrial and marine environments, Earth degassing and its relation to seismicity, volcanic eruptions, rare gases and application of isotope techniques, measurement and analytical techniques. This special issue of Annals of Geophysics collects some of the papers presented dealing with the general problem of the relation between fluids and tectonic activity. Since virtually all geodynamic processes are related to fluids, the conference constituted a further step to enhance our understanding of the special role of gases in the sesismogenic processes