： Over the past two decades, La Soufrière volcano in Guadeloupe has displayed a growing degassing unrest whose actual source mechanism still remains unclear. Based on new measurements of the chemistry and mass flux of fumarolic gas emissions from the volcano, here we reveal spatio-temporal variations in the degassing features that closely relate to the 3D underground circulation of fumarolic fluids, as imaged by electrical resistivity tomography, and to geodetic-seismic signals recorded over the past two decades. Discrete monthly surveys of gas plumes from the various vents on La Soufrière lava dome, performed with portable MultiGAS analyzers, reveal important differences in the chemical proportions and fluxes of H2O, CO2, H2S, SO2 and H2, which depend on the vent location with respect to the underground circulation of fluids. In particular, the main central vents, though directly connected to the volcano conduit and preferentially surveyed in past decades, display much higher CO2/SO2 and H2S/SO2 ratios than peripheral gas emissions, reflecting greater SO2 scrubbing in the boiling hydrothermal water at 80–100 m depth. Gas fluxes demonstrate an increased bulk degassing of the volcano over the past 10 years, but also a recent spatial shift in fumarolic degassing intensity from the center of the lava dome towards its SE–NE sector and the Breislack fracture. Such a spatial shift is in agreement with both extensometric and seismic evidence of fault widening in this sector due to slow gravitational sliding of the southern dome sector. Our study thus provides an improved framework to monitor and interpret the evolution of gas emissions from La Soufrière in the future and to better forecast hazards from this dangerous andesitic volcano.

The use of the Internet must be able to be in confidence for users but security provisioning has a cost for ISPs 1 . In a mobility context this security must be set up from scratch after each handover and for each customer. Therefore, a mechanism has been designed in the standardization bodies: the Context Transfer. This mechanism aims to transfer suitable information between equipments in order to reduce handover time. The benefit for an operator would then be a same security level during and after handover in mobile networks but with a cost as lower as possible. The purpose of this paper is to set out an application of the Context Transfer Protocol to IPsec 2 in a IPv6 mobile environment. After a state of the art of context transfer for security, the paper quickly presents CXTP 3 defined at the IETF 4 . Then, it defines the IPsec context and finally, it describes a CXTP based solution to transfer this context between two access routers in a IPv6 mobility environment.