BBC: Volcanoes are always leaking gas, but a specific change in the composition of the gas could provide an early warning sign that an eruption is imminent. David Pyle of Oxford University and his colleagues examined the dormant Campi Flegrei volcano near Naples, Italy, which last erupted in 1538. They were looking for bubbles of gas that were trapped in molten rock shortly before the eruption. By comparing the composition of the gas in those bubbles with that of gases trapped at other times, the researchers reconstructed the magma's evolution leading up to the eruption. The models revealed that the composition of the gas changed significantly in a relatively short period of time before the eruption. Finding similar evidence at other volcanoes will be necessary to support the theory. If fluctuating gas compositions are a common pattern, monitoring volcanic gas could prove useful for identifying potential eruptions ahead of time.
