In situ measurements of gas discharges across fissures associated with lava flows at Réunion Island

Analysis of gases accumulating at a shallow depth below the ground surface can indicate the presence of fractures and other gas migration routes. nique for sampling and analysis of a range of gases is described, which is fast and mobile and can be applied to gases emitted by an active volcano, as it is particularly suitable for field conditions where little or no laboratory backup is available. sed in conjunction with other geophysical techniques such as seismic and gravity measurements, the methods described aid prediction of the point of emergence of an imminent eruption, leading to improvements in early warning and public safety. r development could make the technique applicable to different types of active volcanoes, and would be particularly useful in areas where a population centre is close to an intermittently active volcano. l analysing carbon dioxide, carbon monoxide, oxygen, methane, hydrogen sulphide and helium was conducted on Piton de la Fournaise, Réunion Island, during an eruptive phase. Results show that a major lava tube was detected, and gradual degassing was measured with increasing distance of the lava from the point of emission.