Constraints on gas release from shallow lake sediments--a case study from the Sea of Galilee

The presence of methane gas in the shallow sub-surface sediments of the Sea of Galilee, northern Israel, has been well documented over the years. Numerous theories for the mechanism responsible for the release of this gas into the water column have been put forth. These include changes in lake levels, seasonality, and seismic activity. The presence of gas in the sediments has been shown to cause acoustic blanking of the seismic signal. In effect, this means that areas of good seismic penetration are areas where gas is not present in the underlying sediment. In this study, 30 years of high-resolution seismic reflection data from the northwestern corner of the lake was examined. This database has allowed for the examination of changes in the spatial extent of gas in the area over time. Results show that the presence or absence of gas in the sediments does not adhere to one clear governing mechanism as previously assumed, but is rather a combination of factors that must be taken into account.